⚠️ Warning: This is a draft ⚠️
This means it might contain formatting issues, incorrect code, conceptual problems, or other severe issues.
If you want to help to improve and eventually enable this page, please fork RosettaGit's repository and open a merge request on GitHub.
{{task|Text processing}} [[Category:Simple]]
;Task: Create a boolean function which takes in a string and tells whether it is a numeric string (floating point and negative numbers included) in the syntax the language uses for numeric literals or numbers converted from strings.
8th
## ActionScript
```actionscript
public function isNumeric(num:String):Boolean
{
return !isNaN(parseInt(num));
}
Ada
The first file is the package interface containing the declaration of the Is_Numeric function.
package Numeric_Tests is
function Is_Numeric (Item : in String) return Boolean;
end Numeric_Tests;
The second file is the package body containing the implementation of the Is_Numeric function.
package body Numeric_Tests is
function Is_Numeric (Item : in String) return Boolean is
Dummy : Float;
begin
Dummy := Float'Value (Item);
return True;
exception
when others =>
return False;
end Is_Numeric;
end Numeric_Tests;
The last file shows how the Is_Numeric function can be called.
with Ada.Text_Io; use Ada.Text_Io;
with Numeric_Tests; use Numeric_Tests;
procedure Is_Numeric_Test is
S1 : String := "152";
S2 : String := "-3.1415926";
S3 : String := "Foo123";
begin
Put_Line(S1 & " results in " & Boolean'Image(Is_Numeric(S1)));
Put_Line(S2 & " results in " & Boolean'Image(Is_Numeric(S2)));
Put_Line(S3 & " results in " & Boolean'Image(Is_Numeric(S3)));
end Is_Numeric_Test;
{{out}}
152 results in TRUE
-3.1415926 results in TRUE
Foo123 results in FALSE
Aime
integer
is_numeric(text s)
{
return !trap_q(alpha, s, 0);
}
integer
main(void)
{
if (!is_numeric("8192&*")) {
o_text("Not numeric.\n");
}
if (is_numeric("8192")) {
o_text("Numeric.\n");
}
return 0;
}
ALGOL 68
{{trans|Ada}}
{{works with|ALGOL 68|Revision 1 - no extensions to language used}}
{{works with|ALGOL 68G|Any - tested with release [http://sourceforge.net/projects/algol68/files/algol68g/algol68g-1.18.0/algol68g-1.18.0-9h.tiny.el5.centos.fc11.i386.rpm/download 1.18.0-9h.tiny]}} {{wont work with|ELLA ALGOL 68|Any (with appropriate job cards) - tested with release [http://sourceforge.net/projects/algol68/files/algol68toc/algol68toc-1.8.8d/algol68toc-1.8-8d.fc9.i386.rpm/download 1.8-8d] - due to extensive use of FORMATted transput}}
PROC is numeric = (REF STRING string) BOOL: (
BOOL out := TRUE;
PROC call back false = (REF FILE f)BOOL: (out:= FALSE; TRUE);
FILE memory;
associate(memory, string);
on value error(memory, call back false);
on logical file end(memory, call back false);
UNION (INT, REAL, COMPL) numeric:=0.0;
# use a FORMAT pattern instead of a regular expression #
getf(memory, ($gl$, numeric));
out
);
test:(
STRING
s1 := "152",
s2 := "-3.1415926",
s3 := "Foo123";
print((
s1, " results in ", is numeric(s1), new line,
s2, " results in ", is numeric(s2), new line,
s3, " results in ", is numeric(s3), new line
))
)
{{out}}
152 results in T
-3.1415926 results in T
Foo123 results in F
ALGOL W
begin
% determnines whether the string contains an integer, real or imaginary %
% number. Returns true if it does, false otherwise %
logical procedure isNumeric( string(32) value text ) ;
begin
logical ok;
% the "number" cannot be blank %
ok := ( text not = " " );
if ok then begin
% there is at least one non-blank character %
% must have either an integer or real/immaginary number %
% integer: [+|-]digit-sequence %
% real: [+|-][digit-sequence].digit-sequence['integer][L] %
% or: [+|-]digit-sequence[.[digit-sequence]]'integer[L] %
% imaginary: %
% [+|-][digit-sequence].digit-sequence['integer][L]I%
% or: [+|-]digit-sequence[.[digit-sequence]]'integer[L]I%
% The "I" at the end of an imaginary number can appear %
% before or after the "L" (which indicates a long number) %
% the "I" and "L" can be in either case %
procedure nextChar ; charPos := charPos + 1;
logical procedure have( string(1) value ch ) ;
( charPos <= maxChar and text(charPos//1) = ch ) ;
logical procedure haveDigit ;
( charPos <= maxChar and text(charPos//1) >= "0" and text(charPos//1) <= "9" ) ;
integer charPos, maxChar;
logical hadDigits, isReal;
charPos := 0;
maxChar := 31;
hadDigits := false;
isReal := false;
% skip trailing spaces %
while maxChar > 0 and text(maxChar//1) = " " do maxChar := maxChar - 1;
% skip leading spacesx %
while have( " " ) do nextChar;
% skip optional sign %
if have( "+" ) or have( "-" ) then nextChar;
if haveDigit then begin
% have a digit sequence %
hadDigits := true;
while haveDigit do nextChar
end if_have_sign ;
if have( "." ) then begin
% real or imaginary number %
nextChar;
isReal := true;
hadDigits := hadDigits or haveDigit;
while haveDigit do nextChar
end if_have_point ;
% should have had some digits %
ok := hadDigits;
if ok and have( "'" ) then begin
% the number has an exponent %
isReal := true;
nextChar;
% skip optional sign %
if have( "+" ) or have( "-" ) then nextChar;
% must have a digit sequence %
ok := haveDigit;
while haveDigit do nextChar;
end if_ok_and_have_exponent ;
% if it is a real number, there could be L/I suffixes %
if ok and isReal then begin
integer LCount, ICount;
LCount := 0;
ICount := 0;
while have( "L" ) or have( "l" ) or have( "I" ) or have( "i" ) do begin
if have( "L" ) or have( "l" )
then LCount := LCount + 1
else ICount := ICount + 1;
nextChar
end while_have_L_or_I ;
% there can be at most one L and at most 1 I %
ok := ( LCount < 2 and ICount < 2 )
end if_ok_and_isReal ;
% must now be at the end if the number %
ok := ok and charPos >= maxChar
end if_ok ;
ok
end isNumeric ;
% test the isNumeric procedure %
procedure testIsNumeric( string(32) value n
; logical value expectedResult
) ;
begin
logical actualResult;
actualResult := isNumeric( n );
write( s_w := 0
, """", n, """ is "
, if actualResult then "" else "not "
, "numeric "
, if actualResult = expectedResult then "" else " NOT "
, "as expected"
)
end testIsNumeric ;
testIsNumeric( "", false );
testIsNumeric( "b", false );
testIsNumeric( ".", false );
testIsNumeric( ".'3", false );
testIsNumeric( "3.'", false );
testIsNumeric( "0.0z44", false );
testIsNumeric( "-1IL", false );
testIsNumeric( "4.5'23ILL", false );
write( "---------" );
testIsNumeric( "-1", true );
testIsNumeric( " +.345", true );
testIsNumeric( "4.5'23I", true );
testIsNumeric( "-5'+3i", true );
testIsNumeric( "-5'-3l", true );
testIsNumeric( " -.345LI", true );
end.
{{out}}
" " is not numeric as expected
"b " is not numeric as expected
". " is not numeric as expected
".'3 " is not numeric as expected
"3.' " is not numeric as expected
"0.0z44 " is not numeric as expected
"-1IL " is not numeric as expected
"4.5'23ILL " is not numeric as expected
---------
"-1 " is numeric as expected
" +.345 " is numeric as expected
"4.5'23I " is numeric as expected
"-5'+3i " is numeric as expected
"-5'-3l " is numeric as expected
" -.345LI " is numeric as expected
Apex
The isNumeric() method is part of the Apex String Class. Note that it will return false if applied to a decimal, because the '.' character is not a Unicode digit.
String numericString = '123456';
String partlyNumericString = '123DMS';
String decimalString = '123.456';
System.debug(numericString.isNumeric()); // this will be true
System.debug(partlyNumericString.isNumeric()); // this will be false
System.debug(decimalString.isNumeric()); // this will be false
System.debug(decimalString.remove('.').isNumeric()); // this will be true
APL
{{works with|Dyalog APL}}
⊃⎕VFI{w←⍵⋄((w='-')/w)←'¯'⋄w}'152 -3.1415926 Foo123'
1 1 0
AppleScript
-- isNumString :: String -> Bool
on isNumString(s)
try
if class of s is string then
set c to class of (s as number)
c is real or c is integer
else
false
end if
on error
false
end try
end isNumString
-- TEST
on run
map(isNumString, {3, 3.0, 3.5, "3.5", "3E8", "-3.5", "30", "three", three, four})
--> {false, false, false, true, true, true, true, false, false, false}
end run
-- three :: () -> Int
script three
3
end script
-- four :: () -> Int
on four()
4
end four
-- GENERIC FUNCTIONS FOR TEST
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
tell mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to lambda(item i of xs, i, xs)
end repeat
return lst
end tell
end map
-- Lift 2nd class handler function into 1st class script wrapper
-- mReturn :: Handler -> Script
on mReturn(f)
if class of f is script then
f
else
script
property lambda : f
end script
end if
end mReturn
{{Out}}
{false, false, false, true, true, true, true, false, false, false}
ARM Assembly
{{works with|as|Raspberry Pi}}
/* ARM assembly Raspberry PI */
/* program strNumber.s */
/* Constantes */
.equ STDIN, 0 @ Linux input console
.equ STDOUT, 1 @ Linux output console
.equ EXIT, 1 @ Linux syscall
.equ READ, 3 @ Linux syscall
.equ WRITE, 4 @ Linux syscall
.equ BUFFERSIZE, 100
/* Initialized data */
.data
szMessNum: .asciz "Enter number : \n"
szMessError: .asciz "String is not a number !!!\n"
szMessInteger: .asciz "String is a integer.\n"
szMessFloat: .asciz "String is a float.\n"
szMessFloatExp: .asciz "String is a float with exposant.\n"
szCarriageReturn: .asciz "\n"
/* UnInitialized data */
.bss
sBuffer: .skip BUFFERSIZE
/* code section */
.text
.global main
main:
loop:
ldr r0,iAdrszMessNum
bl affichageMess
mov r0,#STDIN @ Linux input console
ldr r1,iAdrsBuffer @ buffer address
mov r2,#BUFFERSIZE @ buffer size
mov r7, #READ @ request to read datas
swi 0 @ call system
ldr r1,iAdrsBuffer @ buffer address
mov r2,#0 @ end of string
sub r0,#1 @ replace character 0xA
strb r2,[r1,r0] @ store byte at the end of input string (r0 contains number of characters)
ldr r0,iAdrsBuffer
bl controlNumber @ call routine
cmp r0,#0
bne 1f
ldr r0,iAdrszMessError @ not a number
bl affichageMess
b 5f
1:
cmp r0,#1
bne 2f
ldr r0,iAdrszMessInteger @ integer
bl affichageMess
b 5f
2:
cmp r0,#2
bne 3f
ldr r0,iAdrszMessFloat @ float
bl affichageMess
b 5f
3:
cmp r0,#3
bne 5f
ldr r0,iAdrszMessFloatExp @ float with exposant
bl affichageMess
5:
b loop
100: @ standard end of the program
mov r0, #0 @ return code
mov r7, #EXIT @ request to exit program
svc 0 @ perform system call
iAdrszMessNum: .int szMessNum
iAdrszMessError: .int szMessError
iAdrszMessInteger: .int szMessInteger
iAdrszMessFloat: .int szMessFloat
iAdrszMessFloatExp: .int szMessFloatExp
iAdrszCarriageReturn: .int szCarriageReturn
iAdrsBuffer: .int sBuffer
/******************************************************************/
/* control if string is number */
/******************************************************************/
/* r0 contains the address of the string */
/* r0 return 0 if not a number */
/* r0 return 1 if integer eq 12345 or -12345 */
/* r0 return 2 if float eq 123.45 or 123,45 or -123,45 */
/* r0 return 3 if float with exposant eq 123.45E30 or -123,45E-30 */
controlNumber:
push {r1-r4,lr} @ save registers
mov r1,#0
mov r3,#0 @ point counter
1:
ldrb r2,[r0,r1]
cmp r2,#0
beq 5f
cmp r2,#' '
addeq r1,#1
beq 1b
cmp r2,#'-' @ negative ?
addeq r1,#1
beq 2f
cmp r2,#'+' @ positive ?
addeq r1,#1
2:
ldrb r2,[r0,r1] @ control space
cmp r2,#0 @ end ?
beq 5f
cmp r2,#' '
addeq r1,#1
beq 2b
3:
ldrb r2,[r0,r1]
cmp r2,#0 @ end ?
beq 10f
cmp r2,#'E' @ exposant ?
beq 6f
cmp r2,#'e' @ exposant ?
beq 6f
cmp r2,#'.' @ point ?
addeq r3,#1 @ yes increment counter
addeq r1,#1
beq 3b
cmp r2,#',' @ comma ?
addeq r3,#1 @ yes increment counter
addeq r1,#1
beq 3b
cmp r2,#'0' @ control digit < 0
blt 5f
cmp r2,#'9' @ control digit > 0
bgt 5f
add r1,#1 @ no error loop digit
b 3b
5: @ error detected
mov r0,#0
b 100f
6: @ float with exposant
add r1,#1
ldrb r2,[r0,r1]
cmp r2,#0 @ end ?
moveq r0,#0 @ error
beq 100f
cmp r2,#'-' @ negative exposant ?
addeq r1,#1
mov r4,#0 @ nombre de chiffres
7:
ldrb r2,[r0,r1]
cmp r2,#0 @ end ?
beq 9f
cmp r2,#'0' @ control digit < 0
blt 8f
cmp r2,#'9' @ control digit > 0
bgt 8f
add r1,#1
add r4,#1 @ counter digit
b 7b
8:
mov r0,#0
b 100f
9:
cmp r4,#0 @ number digit exposant = 0 -> error
moveq r0,#0 @ erreur
beq 100f
cmp r4,#2 @ number digit exposant > 2 -> error
movgt r0,#0 @ error
bgt 100f
mov r0,#3 @ valid float with exposant
b 100f
10:
cmp r3,#0
moveq r0,#1 @ valid integer
beq 100f
cmp r3,#1 @ number of point or comma = 1 ?
moveq r0,#2 @ valid float
movgt r0,#0 @ error
100:
pop {r1-r4,lr} @ restaur des 2 registres
bx lr @ return
/******************************************************************/
/* display text with size calculation */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
push {r0,r1,r2,r7,lr} @ save registers
mov r2,#0 @ counter length */
1: @ loop length calculation
ldrb r1,[r0,r2] @ read octet start position + index
cmp r1,#0 @ if 0 its over
addne r2,r2,#1 @ else add 1 in the length
bne 1b @ and loop
@ so here r2 contains the length of the message
mov r1,r0 @ address message in r1
mov r0,#STDOUT @ code to write to the standard output Linux
mov r7, #WRITE @ code call system "write"
svc #0 @ call system
pop {r0,r1,r2,r7,lr} @ restaur registers
bx lr @ return
AutoHotkey
AutoHotkey has no explicitly defined variable types. A variable containing only digits (with an optional decimal point) is automatically interpreted as a number when a math operation or comparison requires it.
list = 0 .14 -5.2 ten 0xf
Loop, Parse, list, %A_Space%
MsgBox,% IsNumeric(A_LoopField)
Return
IsNumeric(x) {
If x is number
Return, 1
Else Return, 0
}
;Output: 1 1 1 0 1
AWK
The following function uses the fact that non-numeric strings in AWK are treated as having the value 0 when used in arithmetics, but not in comparison:
$ awk 'function isnum(x){return(x==x+0)} BEGIN{print isnum("hello"),isnum("-42")}'
{{out}}
0 1
BaCon
INPUT "Your string: ", s$
IF VAL(s$) = 0 AND s$ <> "0" THEN
PRINT "Not a number"
ELSE
PRINT "This is a number"
END IF
{{out}}
user@host $ bacon isnumber.bac
Converting 'isnumber.bac'... done, 7 lines were processed in 0.006 seconds.
Compiling 'isnumber.bac'... cc -c isnumber.bac.c
cc -o isnumber isnumber.bac.o -lbacon -lm
Done, program 'isnumber' ready.
user@host $ ./isnumber
Your string: 12.3
This is a number
user@host $ ./isnumber
Your string: 12E3
This is a number
user@host $ ./isnumber
Your string: PI
Not a number
user@host $ ./isnumber
Your string: Hello
Not a number
BASIC
10 INPUT "Enter a string";S$:GOSUB 1000
20 IF R THEN PRINT "Is num" ELSE PRINT"Not num"
99 END
1000 T1=VAL(S$):T1$=STR$(T1)
1010 R=T1$=S$ OR T1$=" "+S$
1099 RETURN
Batch File
set /a a=%arg%+0 >nul
if %a% == 0 (
if not "%arg%"=="0" (
echo Non Numeric.
) else (
echo Numeric.
)
) else (
echo Numeric.
)
BBC BASIC
{{works with|BBC BASIC for Windows}}
REPEAT
READ N$
IF FN_isanumber(N$) THEN
PRINT "'" N$ "' is a number"
ELSE
PRINT "'" N$ "' is NOT a number"
ENDIF
UNTIL N$ = "end"
END
DATA "PI", "0123", "-0123", "12.30", "-12.30", "123!", "0"
DATA "0.0", ".123", "-.123", "12E3", "12E-3", "12+3", "end"
DEF FN_isanumber(A$)
ON ERROR LOCAL = FALSE
IF EVAL("(" + A$ + ")") <> VAL(A$) THEN = FALSE
IF VAL(A$) <> 0 THEN = TRUE
IF LEFT$(A$,1) = "0" THEN = TRUE
= FALSE
{{out}}
'PI' is NOT a number
'0123' is a number
'-0123' is a number
'12.30' is a number
'-12.30' is a number
'123!' is NOT a number
'0' is a number
'0.0' is a number
'.123' is a number
'-.123' is a number
'12E3' is a number
'12E-3' is a number
'12+3' is NOT a number
'end' is NOT a number
Befunge
~:0\`#v_:"+"-!#v_:"-"-!#v_::"E"-\"e"-*#v_ v
v _v# < < 0<
>~:0\`#v_>::"0"-0\`\"9"-0`+!#v_:"."-!#v_::"E"-\"e"-*!#v_ v
^ $< > > $ v
>~:0\`#v_>::"0"-0\`\"9"-0`+!#v_:"."-!#v_::"E"-\"e"-*!#v_> v>
^ $< >$~:0\`#v_:"+"-#v_v
v $_v# < < :#<
>~:0\`#v_>::"0"-0\`\"9"-0`+!#v_:"."-!#v_::"E"-\"e"-*!v 0 > v
^ $< v < << ^_^#-"-"<
> "ciremuN">:#,_@ >>#$_"ciremun toN">:#,_@^ <
Although only integer inputs are strictly allowed in Befunge, the code tries to adhere to the floating point conventions in other languages when recognising valid numbers.
{{out}}
'PI' Not numeric
'0123' Numeric
'-0123' Numeric
'12.30' Numeric
'-12.30' Numeric
'123!' Not numeric
'0' Numeric
'0.0' Numeric
'.123' Numeric
'-.123' Numeric
'12E3' Numeric
'12E-3' Numeric
'12+3' Not numeric
'end' Not numeric
'12..34' Not numeric
'12e3.4' Not numeric
'192.168.0.1' Not numeric
Bracmat
To check whether a string is a number, a fraction or an integer, use the patterns #, / and ~/# ("not a fraction and yet a number"). In the pattern matching examples below (which can be typed in at the Bracmat prompt) F denotes 'failure' and S denotes 'success'.
43257349578692:/
F
260780243875083/35587980:/
S
247/30:~/#
F
80000000000:~/#
S
Bracmat doesn't do floating point computations (historical reason: the Acorn Risc Machine a.k.a. ARM processor in the Archimedes computer did not have an FPU), but the pattern /# (|"." (|? 0|`) (|/#:>0)) (|(E|e) ~/#)
@("1.000-4E-10":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
F
@("1.0004E-54328":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
@("-464641.0004E-54328":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
@("1/2.0004E-10":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
F
@("1357E-10":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
@("1357e0":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
@("13579":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
@("1.246":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
@("0.0":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
@("0.0000":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
S
To do computations with such "floating point strings" you would have to convert such strings to fractional representations first.
(float2fraction=
integerPart decimalPart d1 dn exp sign
. @( !arg
: ~/#?integerPart
( &0:?decimalPart:?d1:?dn
| "."
[?d1
(|? 0|`)
( &0:?decimalPart
| ~/#?decimalPart:>0
)
[?dn
)
( &0:?exp
| (E|e) ~/#?exp
)
)
& ( !integerPart*(-1:?sign):>0:?integerPart
| 1:?sign
)
& !sign*(!integerPart+!decimalPart*10^(!d1+-1*!dn))*10^!exp
);
( out$float2fraction$"1.2"
& out$float2fraction$"1.02"
& out$float2fraction$"1.01"
& out$float2fraction$"10.01"
& out$float2fraction$"10.01e10"
& out$float2fraction$"10.01e1"
& out$float2fraction$"10.01e2"
& out$float2fraction$"10.01e-2"
& out$float2fraction$"-10.01e-2"
& out$float2fraction$"-10e-2"
& out$float2fraction$"0.000"
);
{{out}}
6/5
51/50
101/100
1001/100
100100000000
1001/10
1001
1001/10000
-1001/10000
-1/10
0
Burlesque
ps^^-]to{"Int""Double"}\/~[\/L[1==?*
Assumes string is not empty.
C
Returns true (non-zero) if character-string parameter represents a signed or unsigned floating-point number. Otherwise returns false (zero).
#include <ctype.h>
#include <stdlib.h>
int isNumeric (const char * s)
{
if (s == NULL || *s == '\0' || isspace(*s))
return 0;
char * p;
strtod (s, &p);
return *p == '\0';
}
C++
Using stringstream:
#include <sstream>
// for istringstream
using namespace std;
bool isNumeric( const char* pszInput, int nNumberBase )
{
istringstream iss( pszInput );
if ( nNumberBase == 10 )
{
double dTestSink;
iss >> dTestSink;
}
else if ( nNumberBase == 8 || nNumberBase == 16 )
{
int nTestSink;
iss >> ( ( nNumberBase == 8 ) ? oct : hex ) >> nTestSink;
}
else
return false;
// was any input successfully consumed/converted?
if ( ! iss )
return false;
// was all the input successfully consumed/converted?
return ( iss.rdbuf()->in_avail() == 0 );
}
Using find:
bool isNumeric( const char* pszInput, int nNumberBase )
{
string base = "0123456789ABCDEF";
string input = pszInput;
return (input.find_first_not_of(base.substr(0, nNumberBase)) == string::npos);
}
Using all_of (requires C++11)
bool isNumeric(const std::string& input) {
return std::all_of(input.begin(), input.end(), ::isdigit);
}
C#
'''Framework:''' [[.NET]] 2.0+
public static bool IsNumeric(string s)
{
double Result;
return double.TryParse(s, out Result); // TryParse routines were added in Framework version 2.0.
}
string value = "123";
if (IsNumeric(value))
{
// do something
}
'''Framework:''' [[.NET]] 1.0+
public static bool IsNumeric(string s)
{
try
{
Double.Parse(s);
return true;
}
catch
{
return false;
}
}
Clojure
(defn numeric? [s]
(if-let [s (seq s)]
(let [s (if (= (first s) \-) (next s) s)
s (drop-while #(Character/isDigit %) s)
s (if (= (first s) \.) (next s) s)
s (drop-while #(Character/isDigit %) s)]
(empty? s))))
This works with any sequence of characters, not just Strings, e.g.:
(numeric? [\1 \2 \3]) ;; yields logical true
COBOL
Intrinsic Functions
COBOL has the intrinsic functions TEST-NUMVAL and TEST-NUMVAL-C to check if a string is numeric (TEST-NUMVAL-C is used to check if it is also a monetary string). Implementations supporting the 20XX draft standard can also use TEST-NUMVAL-F for floating-point numbers. They return 0 if the string is valid, or the position of the first incorrect character.
program-id. is-numeric.
procedure division.
display function test-numval-f("abc") end-display
display function test-numval-f("-123.01E+3") end-display
if function test-numval-f("+123.123") equal zero then
display "is numeric" end-display
else
display "failed numval-f test" end-display
end-if
goback.
Implementation
{{works with|OpenCOBOL}}
IDENTIFICATION DIVISION.
PROGRAM-ID. Is-Numeric.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 Numeric-Chars PIC X(10) VALUE "0123456789".
01 Success CONSTANT 0.
01 Failure CONSTANT 128.
LOCAL-STORAGE SECTION.
01 I PIC 99.
01 Num-Decimal-Points PIC 99.
01 Num-Valid-Chars PIC 99.
LINKAGE SECTION.
01 Str PIC X(30).
PROCEDURE DIVISION USING Str.
IF Str = SPACES
MOVE Failure TO Return-Code
GOBACK
END-IF
MOVE FUNCTION TRIM(Str) TO Str
INSPECT Str TALLYING Num-Decimal-Points FOR ALL "."
IF Num-Decimal-Points > 1
MOVE Failure TO Return-Code
GOBACK
ELSE
ADD Num-Decimal-Points TO Num-Valid-Chars
END-IF
IF Str (1:1) = "-" OR "+"
ADD 1 TO Num-Valid-Chars
END-IF
PERFORM VARYING I FROM 1 BY 1 UNTIL I > 10
INSPECT Str TALLYING Num-Valid-Chars
FOR ALL Numeric-Chars (I:1) BEFORE SPACE
END-PERFORM
INSPECT Str TALLYING Num-Valid-Chars FOR TRAILING SPACES
IF Num-Valid-Chars = FUNCTION LENGTH(Str)
MOVE Success TO Return-Code
ELSE
MOVE Failure TO Return-Code
END-IF
GOBACK
.
CoffeeScript
The isFinite function is built into JavaScript, so we don't need to create our own function in CoffeeScript.
console.log (isFinite(s) for s in [5, "5", "-5", "5", "5e5", 0]) # all true
console.log (isFinite(s) for s in [NaN, "fred", "###"]) # all false
ColdFusion
Adobe's ColdFusion
TestValue: <cfoutput>#TestValue#</cfoutput>
<cfif isNumeric(TestValue)>
is Numeric.
<cfelse>
is NOT Numeric.
</cfif>
<cfset TestValue="NAS">
TestValue: <cfoutput>#TestValue#</cfoutput>
<cfif isNumeric(TestValue)>
is Numeric.
<cfelse>
is NOT Numeric.
</cfif>
Alternative solution
## CFScript
ColdFusion Script (CfScript)
```cfm
isNumeric(42)
Common Lisp
If the input may be relied upon to not be especially malicious, then it may be ''read'' and the result checked for being a number.
(defun numeric-string-p (string)
(let ((*read-eval* nil))
(ignore-errors (numberp (read-from-string string)))))
ignore-errors here handles returning nil in case the input is invalid rather than simply non-numeric.
However, read[-from-string] has the side effect of interning any symbols encountered, and can have memory allocation larger than the input size (due to read syntax such as #*, which takes a length). The [http://www.cliki.net/PARSE-NUMBER parse-number] library provides a numbers-only equivalent of read.
(defun numeric-string-p (string)
(ignore-errors (parse-number:parse-number string))) ; parse failed, return false (nil)
D
Standard Version
Using the standard Phobos function (currently binary and hex literals are not recognized):
import std.stdio, std.string, std.array;
void main() {
foreach (const s; ["12", " 12\t", "hello12", "-12", "02",
"0-12", "+12", "1.5", "1,000", "1_000",
"0x10", "0b10101111_11110000_11110000_00110011",
"-0b10101", "0x10.5"])
writefln(`isNumeric("%s"): %s`, s, s.strip().isNumeric(true));
}
{{out}}
isNumeric("12"): true
isNumeric(" 12 "): true
isNumeric("hello12"): false
isNumeric("-12"): true
isNumeric("02"): true
isNumeric("0-12"): false
isNumeric("+12"): true
isNumeric("1.5"): true
isNumeric("1,000"): true
isNumeric("1_000"): true
isNumeric("0x10"): false
isNumeric("0b10101111_11110000_11110000_00110011"): false
isNumeric("-0b10101"): false
isNumeric("0x10.5"): false
An Implementation
import std.stdio, std.string, std.conv, std.array, std.exception;
bool isNumeric(in string s) pure {
immutable s2 = s.strip.toLower.replace("_", "").replace(",", "");
try {
s2.to!real;
} catch (ConvException e) {
if (s2.startsWith("0x"))
return !s2[2 .. $].to!ulong(16)
.collectException!ConvException;
else if (s2.startsWith("0b"))
return !s2[2 .. $].to!ulong(2)
.collectException!ConvException;
else
return false;
}
return true;
}
void main() {
foreach (immutable s; ["12", " 12\t", "hello12", "-12", "02",
"0-12", "+12", "1.5", "1,000", "1_000",
"0x10", "0b10101111_11110000_11110000_00110011",
"-0b10101", "0x10.5"])
writefln(`isNumeric("%s"): %s`, s, s.isNumeric);
}
{{out}}
isNumeric("12"): true
isNumeric(" 12 "): true
isNumeric("hello12"): false
isNumeric("-12"): true
isNumeric("02"): true
isNumeric("0-12"): false
isNumeric("+12"): true
isNumeric("1.5"): true
isNumeric("1,000"): true
isNumeric("1_000"): true
isNumeric("0x10"): true
isNumeric("0b10101111_11110000_11110000_00110011"): true
isNumeric("-0b10101"): false
isNumeric("0x10.5"): false
=={{header|Déjà Vu}}==
is-numeric s:
true
try:
drop to-num s
catch value-error:
not
for v in [ "1" "0" "3.14" "hello" "12e3" "12ef" "-3" ]:
!.( v is-numeric v )
{{out}}
"-3" true
"12ef" false
"12e3" true
"hello" false
"3.14" true
"0" true
"1" true
Delphi
This simple function is a wrapper around a built-in Delphi function
function IsNumericString(const inStr: string): Boolean;
var
i: extended;
begin
Result := TryStrToFloat(inStr,i);
end;
This console application tests the function:
program isNumeric;
{$APPTYPE CONSOLE}
uses
Classes,
SysUtils;
function IsNumericString(const inStr: string): Boolean;
var
i: extended;
begin
Result := TryStrToFloat(inStr,i);
end;
{ Test function }
var
s: string;
c: Integer;
const
MAX_TRIES = 10;
sPROMPT = 'Enter a string (or type "quit" to exit):';
sIS = ' is numeric';
sISNOT = ' is NOT numeric';
begin
c := 0;
s := '';
repeat
Inc(c);
Writeln(sPROMPT);
Readln(s);
if (s <> '') then
begin
tmp.Add(s);
if IsNumericString(s) then
begin
Writeln(s+sIS);
end
else
begin
Writeln(s+sISNOT);
end;
Writeln('');
end;
until
(c >= MAX_TRIES) or (LowerCase(s) = 'quit');
end.
{{out}} Example summarised:
123 is numeric
-123.456 is numeric
-123.-456 is NOT numeric
.345 is numeric
m1k3 is NOT numeric
Dyalect
func String.isNumeric() {
try {
var o = parse(this)
o.getType() == Integer || o.getType() == Float
} catch _ {
false
}
}
var str = "1234567"
print(str.isNumeric())
E
def isNumeric(specimen :String) {
try {
<import:java.lang.makeDouble>.valueOf(specimen)
return true
} catch _ {
return false
}
}
EasyLang
because every variable must be used
h# = h# + h .
test$[] = [ "abc" "21a" "1234" "-13" "7.65" ] for i range len test$[] call is_numeric test$[i] r if r = 1 print test$[i] & " is numeric" else print test$[i] & " is not numeric" . .
## EchoLisp
The conversion function '''string->number''' returns #f - false - in the string is not a number, else returns a number, which is #t - true - as far as logical operations are concerned
```scheme
(string->number "albert")
→ #f
(string->number -666)
→ -666
(if (string->number 666) 'YES 'NO)
→ YES
Elixir
defmodule RC do
def is_numeric(str) do
case Float.parse(str) do
{_num, ""} -> true
_ -> false
end
end
end
["123", "-12.3", "123.", ".05", "-12e5", "+123", " 123", "abc", "123a", "12.3e", "1 2"] |> Enum.filter(&RC.is_numeric/1)
{{out}}
["123", "-12.3", "-12e5", "+123"]
Erlang
Erlang doesn't come with a way to say if a string represents a numeric value or not, but does come with the built-in function is_number/1, which will return true if the argument passed is either an integer or a float. Erlang also has two functions to transform a string to either a floating number or an integer, which will be used in conjunction with is_number/1.
is_numeric(L) ->
Float = (catch erlang:list_to_float(L)),
Int = (catch erlang:list_to_integer(L)),
is_number(Float) orelse is_number(Int).
ERRE
Short form using predeclared ERRE functions VAL and STR$.
PROGRAM NUMERIC
PROCEDURE IS_NUMERIC(S$->ANS%)
LOCAL T1,T1$
T1=VAL(S$)
T1$=STR$(T1)
ANS%=(T1$=S$) OR T1$=" "+S$
END PROCEDURE
BEGIN
PRINT(CHR$(12);)
INPUT("Enter a string",S$)
IS_NUMERIC(S$->ANS%)
IF ANS% THEN PRINT("is num") ELSE PRINT("not num")
END PROGRAM
{{out}}
Enter a string? 12.30
is num
Euphoria
include get.e
function is_numeric(sequence s)
sequence val
val = value(s)
return val[1]=GET_SUCCESS and atom(val[2])
end function
=={{header|F_Sharp|F#}}==
let is_numeric a = fst (System.Double.TryParse(a))
Factor
: numeric? ( string -- ? ) string>number >boolean ;
Fantom
The 'fromStr' methods return a parsed number or given an error. The 'false' tells each method to return null if the string does not parse as a number of given type, otherwise, the 'fromStr' method throws an exception.
class Main
{
// function to see if str contains a number of any of built-in types
static Bool readNum (Str str)
{
int := Int.fromStr (str, 10, false) // use base 10
if (int != null) return true
float := Float.fromStr (str, false)
if (float != null) return true
decimal := Decimal.fromStr (str, false)
if (decimal != null) return true
return false
}
public static Void main ()
{
echo ("For '2': " + readNum ("2"))
echo ("For '-2': " + readNum ("-2"))
echo ("For '2.5': " + readNum ("2.5"))
echo ("For '2a5': " + readNum ("2a5"))
echo ("For '-2.1e5': " + readNum ("-2.1e5"))
}
}
{{out}}
For '2': true
For '-2': true
For '2.5': true
For '2a5': false
For '-2.1e5': true
Forth
{{works with|gforth|0.6.2}}
: is-numeric ( addr len -- )
2dup snumber? ?dup if \ not standard, but >number is more cumbersome to use
0< if
-rot type ." as integer = " .
else
2swap type ." as double = " <# #s #> type
then
else 2dup >float if
type ." as float = " f.
else
type ." isn't numeric in base " base @ dec.
then then ;
s" 1234" is-numeric \ 1234 as integer = 1234
s" 1234." is-numeric \ 1234. as double = 1234
s" 1234e" is-numeric \ 1234e as float = 1234.
s" $1234" is-numeric \ $1234 as integer = 4660 ( hex literal )
s" %1010" is-numeric \ %1010 as integer = 10 ( binary literal )
s" beef" is-numeric \ beef isn't numeric in base 10
hex
s" beef" is-numeric \ beef as integer = BEEF
s" &1234" is-numeric \ &1234 as integer = 4D2 ( decimal literal )
Fortran
FUNCTION is_numeric(string)
IMPLICIT NONE
CHARACTER(len=*), INTENT(IN) :: string
LOGICAL :: is_numeric
REAL :: x
INTEGER :: e
READ(string,*,IOSTAT=e) x
is_numeric = e == 0
END FUNCTION is_numeric
FreeBASIC
FreeBASIC has a built-in Val() function which converts numeric strings to doubles. However, it is not ideal for the present task since it will try to convert as much of the string as it can (so "123xyz" would convert to 123) and return 0 if a conversion on this basis is not possible (i.e. "xyz" would return 0).
I've therefore written a custom function which recognizes signed numbers in bases from 2 to 16 (but only integral numbers for bases other than 10). For base 10, it will treat "123." or ".123" as numbers but not ".". It doesn't recognize scientific notation but does recognize the integral prefixes &H, &O and &B if bases 16, 8 or 2 respectively are specified.
' FB 1.05.0 Win64
Dim Shared symbols(0 To 15) As UByte
For i As Integer = 48 to 57
symbols(i - 48) = i
Next
For i As Integer = 97 to 102
symbols(i - 87) = i
Next
Const plus As UByte = 43
Const minus As Ubyte = 45
Const dot As UByte = 46
Function isNumeric(s As Const String, base_ As Integer = 10) As Boolean
If s = "" OrElse s = "." OrElse s = "+" OrElse s = "-" Then Return False
Err = 0
If base_ < 2 OrElse base_ > 16 Then
Err = 1000
Return False
End If
Dim t As String = LCase(s)
If (t[0] = plus) OrElse (t[0] = minus) Then
t = Mid(t, 2)
End If
If Left(t, 2) = "&h" Then
If base_ <> 16 Then Return False
t = Mid(t, 3)
End if
If Left(t, 2) = "&o" Then
If base_ <> 8 Then Return False
t = Mid(t, 3)
End if
If Left(t, 2) = "&b" Then
If base_ <> 2 Then Return False
t = Mid(t, 3)
End if
If Len(t) = 0 Then Return False
Dim As Boolean isValid, hasDot = false
For i As Integer = 0 To Len(t) - 1
isValid = False
For j As Integer = 0 To base_ - 1
If t[i] = symbols(j) Then
isValid = True
Exit For
End If
If t[i] = dot Then
If CInt(Not hasDot) AndAlso (base_ = 10) Then
hasDot = True
IsValid = True
Exit For
End If
Return False ' either more than one dot or not base 10
End If
Next j
If Not isValid Then Return False
Next i
Return True
End Function
Dim s As String
s = "1234.056789"
Print s, " (base 10) => "; isNumeric(s)
s = "1234.56"
Print s, " (base 7) => "; isNumeric(s, 7)
s = "021101"
Print s, " (base 2) => "; isNumeric(s, 2)
s = "Dog"
Print s, " (base 16) => "; isNumeric(s, 16)
s = "Bad125"
Print s, " (base 16) => "; isNumeric(s, 16)
s = "-0177"
Print s, " (base 8) => "; isNumeric(s, 8)
s = "+123abcd.ef"
Print s, " (base 16) => "; isNumeric(s, 8)
s = "54321"
Print s, " (base 6) => "; isNumeric(s, 6)
s = "123xyz"
Print s, " (base 10) => "; isNumeric(s)
s = "xyz"
Print s, " (base 10) => "; isNumeric(s)
Print
Print "Press any key to quit"
Sleep
{{out}}
1234.056789 (base 10) => true
1234.56 (base 7) => false
021101 (base 2) => false
Dog (base 16) => false
Bad125 (base 16) => true
-0177 (base 8) => true
+123abcd.ef (base 16) => false
54321 (base 6) => true
123xyz (base 10) => false
xyz (base 10) => false
Free Pascal
function isNumeric(const potentialNumeric: string): boolean;
var
potentialInteger: integer;
potentialReal: real;
integerError: integer;
realError: integer;
begin
integerError := 0;
realError := 0;
// system.val attempts to convert numerical value representations.
// It accepts all notations as they are accepted by the language,
// as well as the '0x' (or '0X') prefix for hexadecimal values.
val(potentialNumeric, potentialInteger, integerError);
val(potentialNumeric, potentialReal, realError);
isNumeric := (integerError = 0) or (realError = 0);
end;
Gambas
Public Sub Form_Open()
Dim sAnswer, sString As String
sString = Trim(InputBox("Enter as string", "String or Numeric"))
If IsNumber(sString) Then sAnswer = "'" & sString & "' is numeric" Else sAnswer = "'" & sString & "' is a string"
Print sAnswer
End
Output:
'Charlie' is a string
'-00.256666' is numeric
Go
import "strconv"
func IsNumeric(s string) bool {
_, err := strconv.ParseFloat(s, 64)
return err == nil
}
Groovy
Use the positional parser in java.text.NumberFormat. If, after parsing, the parse position is at the end of the string, we can deduce that the entire string was a valid number.
def isNumeric = {
def formatter = java.text.NumberFormat.instance
def pos = [0] as java.text.ParsePosition
formatter.parse(it, pos)
// if parse position index has moved to end of string
// them the whole string was numeric
pos.index == it.size()
}
Test Program:
println isNumeric('1')
println isNumeric('-.555')
println isNumeric('1,000,000')
println isNumeric(' 1 1 1 1 ')
println isNumeric('abcdef')
{{out}}
true
true
true
false
false
Haskell
This function is not particularly useful in a statically typed language. Instead, one would just attempt to convert the string to the desired type with ''read'' or ''reads'', and handle parsing failure appropriately.
The task doesn't define which strings are considered "numeric", so we do Integers and Doubles, which should catch the most common cases (including hexadecimal 0x notation):
isInteger s = case reads s :: [(Integer, String)] of
[(_, "")] -> True
_ -> False
isDouble s = case reads s :: [(Double, String)] of
[(_, "")] -> True
_ -> False
isNumeric :: String -> Bool
isNumeric s = isInteger s || isDouble s
One can easily add ''isRational'', ''isComplex'' etc. following the same pattern.
Another way would be to use the Data.Char module, allowing code such as:
areDigits = all isDigit
isDigit selects ASCII digits i.e. '0'..'9'
isOctDigit selects '0'..'7'
isHexDigit selects '0'..'9','A'..'F','a'..'f'
so read s::Int (for instance) could be reliably used if string s passed these tests.
Haxe
Haxe has a built-in function that will convert a string to an integer, so we can use that to determine if the string is numeric or not.
static function isNumeric(n:String):Bool
{
if (Std.parseInt(n) != null) //Std.parseInt converts a string to an int
{
return true; //as long as it results in an integer, the function will return true
}
else
{
return false;
}
}
HicEst
! = bin + 2*int + 4*flt + 8*oct +16*hex + 32*sci
isNumeric("1001") ! 27 = 1 1 0 1 1 0
isNumeric("123") ! 26 = 0 1 0 1 1 0
isNumeric("1E78") ! 48 = 0 0 0 0 1 1
isNumeric("-0.123") ! 4 = 0 0 1 0 0 1
isNumeric("-123.456e-78") ! 32 = 0 0 0 0 0 1
isNumeric(" 123") ! 0: leading blank
isNumeric("-123.456f-78") ! 0: illegal character f
FUNCTION isNumeric(string) ! true ( > 0 ), no leading/trailing blanks
CHARACTER string
b = INDEX(string, "[01]+", 128, Lbin) ! Lbin returns length found
i = INDEX(string, "-?\d+", 128, Lint) ! regular expression: 128
f = INDEX(string, "-?\d+\.\d*", 128, Lflt)
o = INDEX(string, "[0-7]+", 128, Loct)
h = INDEX(string, "[0-9A-F]+", 128, Lhex) ! case sensitive: 1+128
s = INDEX(string, "-?\d+\.*\d*E[+-]*\d*", 128, Lsci)
IF(anywhere) THEN ! 0 (false) by default
isNumeric = ( b > 0 ) + 2*( i > 0 ) + 4*( f > 0 ) + 8*( o > 0 ) + 16*( h > 0 ) + 32*( s > 0 )
ELSEIF(boolean) THEN ! 0 (false) by default
isNumeric = ( b + i + f + o + h + s ) > 0 ! this would return 0 or 1
ELSE
L = LEN(string)
isNumeric = (Lbin==L) + 2*(Lint==L) + 4*(Lflt==L) + 8*(Loct==L) + 16*(Lhex==L) + 32*(Lsci==L)
ENDIF
END
i
concept numeric(n) {
number(n)
errors {
print(n, " is not numeric!")
return
}
print(n, " is numeric :)")
}
software {
numeric("1200")
numeric("3.14")
numeric("3/4")
numeric("abcdefg")
numeric("1234test")
}
=={{header|Icon}} and {{header|Unicon}}== The code writes a printable image of x whatever type it is and a statement about whether it is numeric or not. Icon and Unicon use success and failure instead of boolean functions, numeric(x) is built-in and returns x or fails.
write(image(x), if numeric(x) then " is numeric." else " is not numeric")
IDL
function isnumeric,input
on_ioerror, false
test = double(input)
return, 1
false: return, 0
end
Could be called like this:
if isnumeric('-123.45e-2') then print, 'yes' else print, 'no'
; ==> yes
if isnumeric('picklejuice') then print, 'yes' else print, 'no'
; ==> no
J
isNumeric=: _ ~: _ ". ]
isNumericScalar=: 1 -: isNumeric
TXT=: ,&' a scalar numeric value.' &.> ' is not';' represents'
sayIsNumericScalar=: , TXT {::~ isNumericScalar
Examples of use:
isNumeric '152'
1
isNumeric '152 -3.1415926 Foo123'
1 1 0
isNumeric '42 foo42 4.2e1 4200e-2 126r3 16b2a 42foo'
1 0 1 1 1 1 0
isNumericScalar '152 -3.1415926 Foo123'
0
sayIsNumericScalar '-3.1415926'
-3.1415926 represents a scalar numeric value.
Java
It's generally bad practice in Java to rely on an exception being thrown since exception handling is relatively expensive. If non-numeric strings are common, you're going to see a huge performance hit.
public boolean isNumeric(String input) {
try {
Integer.parseInt(input);
return true;
}
catch (NumberFormatException e) {
// s is not numeric
return false;
}
}
Alternative 1 : Check that each character in the string is number. Note that this will only works for integers.
private static final boolean isNumeric(final String s) {
if (s == null || s.isEmpty()) return false;
for (int x = 0; x < s.length(); x++) {
final char c = s.charAt(x);
if (x == 0 && (c == '-')) continue; // negative
if ((c >= '0') && (c <= '9')) continue; // 0 - 9
return false; // invalid
}
return true; // valid
}
Alternative 2 : use a regular expression (a more elegant solution).
public static boolean isNumeric(String inputData) {
return inputData.matches("[-+]?\\d+(\\.\\d+)?");
}
Alternative 3 : use the positional parser in the java.text.NumberFormat object (a more robust solution). If, after parsing, the parse position is at the end of the string, we can deduce that the entire string was a valid number.
public static boolean isNumeric(String inputData) {
NumberFormat formatter = NumberFormat.getInstance();
ParsePosition pos = new ParsePosition(0);
formatter.parse(inputData, pos);
return inputData.length() == pos.getIndex();
}
Alternative 4 : use the java.util.Scanner object. Very useful if you have to scan multiple entries.
public static boolean isNumeric(String inputData) {
Scanner sc = new Scanner(inputData);
return sc.hasNextInt();
}
Scanner also has similar methods for longs, shorts, bytes, doubles, floats, BigIntegers, and BigDecimals as well as methods for integral types where you may input a base/radix other than 10 (10 is the default, which can be changed using the useRadix method).
JavaScript
A far better validator can be found on StackOverflow[http://stackoverflow.com/questions/18082/validate-numbers-in-javascript-isnumeric]
function isNumeric(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
var value = "123.45e7"; // Assign string literal to value
if (isNumeric(value)) {
// value is a number
}
//Or, in web browser in address field:
// javascript:function isNumeric(n) {return !isNaN(parseFloat(n)) && isFinite(n);}; value="123.45e4"; if(isNumeric(value)) {alert('numeric')} else {alert('non-numeric')}
jq
In versions of jq that support try/catch, the simplest way to test if a string can be parsed as a number is:
The above expression will emit the corresponding number, or false if there is none. Here then is a boolean filter which will also emit true for each input that is a number:
```jq
def is_numeric: true and try tonumber catch false;
Julia
The function isnumeric tests for strings that parse directly to numbers. This test excludes symbols, such as π and 1 + 1, that evaluate to numbers as well as certain elaborate numbers (large integers, rationals and complex numbers) whose literals parse to expressions that must be evaluated to yield numbers.
using Printf
isnumeric(s::AbstractString) = tryparse(Float64, s) isa Number
tests = ["1", "-121", "one", "pi", "1 + 1", "NaN", "1234567890123456789", "1234567890123456789123456789",
"1234567890123456789123456789.0", "1.3", "1.4e10", "Inf", "1//2", "1.0 + 1.0im"]
for t in tests
fl = isnumeric(t) ? "is" : "is not"
@printf("%35s %s a direct numeric literal.\n", t, fl)
end
{{out}}
1 is a direct numeric literal.
-121 is a direct numeric literal.
one is not a direct numeric literal.
pi is not a direct numeric literal.
1 + 1 is not a direct numeric literal.
NaN is a direct numeric literal.
1234567890123456789 is a direct numeric literal.
1234567890123456789123456789 is a direct numeric literal.
1234567890123456789123456789.0 is a direct numeric literal.
1.3 is a direct numeric literal.
1.4e10 is a direct numeric literal.
Inf is a direct numeric literal.
1//2 is not a direct numeric literal.
1.0 + 1.0im is not a direct numeric literal.
Kotlin
// version 1.1
fun isNumeric(input: String): Boolean =
try {
input.toDouble()
true
} catch(e: NumberFormatException) {
false
}
fun main(args: Array<String>) {
val inputs = arrayOf("152", "-3.1415926", "Foo123", "-0", "456bar", "1.0E10")
for (input in inputs) println("$input is ${if (isNumeric(input)) "numeric" else "not numeric"}")
}
{{out}}
152 is numeric
-3.1415926 is numeric
Foo123 is not numeric
-0 is numeric
456bar is not numeric
1.0E10 is numeric
LabVIEW
{{VI solution|LabVIEW_Determine_if_a_string_is_numeric.png}}
Lasso
{{works with|Lasso|8 & 9 }}
local(str='12345')
string_isNumeric(#str) // true
{{works with|Lasso|9}}
'12345'->isdigit // true
'1X34Q'->isdigit // false
Liberty BASIC
DATA "PI", "0123", "-0123", "12.30", "-12.30", "123!", "0"
DATA "0.0", ".123", "-.123", "12E3", "12E-3", "12+3", "end"
while n$ <> "end"
read n$
print n$, IsNumber(n$)
wend
end
function IsNumber(string$)
on error goto [NotNumber]
string$ = trim$(string$)
'check for float overflow
n = val(string$)
'assume it is number and try to prove wrong
IsNumber = 1
for i = 1 to len(string$)
select case mid$(string$, i, 1)
case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"
HasNumeric = 1 'to check if there are any digits
case "e", "E"
'"e" must not occur more than once
'must not occur before digits
if HasE > 0 or HasNumeric = 0 then
IsNumber = 0
exit for
end if
HasE = i 'store position of "e"
HasNumeric = 0 'needs numbers after "e"
case "-", "+"
'must be either first character or immediately after "e"
'(HasE = 0 if no occurrences yet)
if HasE <> i-1 then
IsNumber = 0
exit for
end if
case "."
'must not have previous points and must not come after "e"
if HasE <> 0 or HasPoint <> 0 then
IsNumber = 0
exit for
end if
HasPoint = 1
case else
'no other characters allowed
IsNumber = 0
exit for
end select
next i
'must have digits
if HasNumeric = 0 then IsNumber = 0
[NotNumber]
end function
Lisaac
"123457".is_integer.println;
// write TRUE on stdin
Logo
show number? "-1.23 ; true
Lua
This will also accept strings like "0xFF" or "314.16e-2" as numbers.
if tonumber(a) ~= nil then
--it's a number
end;
M2000 Interpreter
We have to define our IsNumber() Version 2 handle decimal point character. For code M2000 use dot, but for input and output use the user specified decimal point, from OS. Function Str$(1.2) return a string with a dot always, but if we place a second parameter this change. Print str$(1.2, "") maybe return 1,2 and nor 1.2. Print str$(1.2, "#.00") maybe return 1.20 or 1,20. The reverse function is Val() which can take more characters so A Val("121mm") is 121, and with a second parameter we can interpret properly the decimal dot: Print Val("1.2", ".") always return 1.2 double. Print Val("1,2", ",")=1.2 return true, 1.2 is a m2000 number literal and always has a dot.
\\ version 2
Module Checkit {
function global isNumber(a$, de$=".") {
=false=true ' return boolean
if de$="" then de$=str$(.1,".") ' get current decimal point character
a$=trim$(ucase$(a$))
m=len(a$)
if m=0 then exit
c$=filter$(a$,"0123456789")
if c$ = "" then {
=true
} else.if m>1 then {
\ may have -+ and ,
if m=2 then {
if not c$~"[-+\"+de$+"]" then break
} else {
if left$(c$,1 ) ~"[+-]" then c$=mid$(c$, 2)
if not (c$=de$ or c$=de$+"E" or c$ ~ de$+"E[+-]") then break
if c$ ~ de$+"E[+-]" then if not (instr(a$,"E+")>0 or instr(a$,"E-")>0) then break
}
if de$<>"." then a$=replace$(de$, ".", a$, 1,1)
try {inline "a="+a$+"=="+a$}
if valid(a) then =a = true=true ' return boolean
}
}
Print isNumber("+1"), isnumber("-1"), isNumber("1+")=false, isnumber("1-")=false
Print isNumber(",1",","), isnumber("1,",","), isNumber(",0",","), isnumber("0,", ",")
Print isNumber(".1"), isnumber("1."), isNumber(".0"), isnumber("0.")
Print isNumber("+.1"), isnumber("-1."), isNumber(".12e+232"), isnumber("0.122e10")
Print isNumber("+.1a")=false, isnumber("asasa1212")=false, isNumber("1.2e43+23")=false, isnumber("0.122e10")
Print isNumber("1221.211.1221")=false, isnumber("1221e1212")=false, isNumber("1.2e4323")=false, isnumber("-.122e-10")
}
Checkit
From rev.31 Version 9.3 Val function update, to include a more quick version of above. We have to specify the dot char or write any two or more chars for dot to get integer part. Val function return number and in third argument (passing by reference by default) return first position in string after number. If string is empty or have no number then position is -1. If a number found position is >1. Leading spaces trimmed.
Function IsNumeric(a$) {
def m
=val(false->boolean)
Try {
if islet then {
z=val(a$,letter$, m)
} else.if isnum then {
z=val(a$,number, m)
} else z=val(a$,"", m)
=m>len(a$)
}
}
Function IsIntegerNumeric(a$) {
def m
=val(false->boolean)
Try {
z=val(a$,"Int", m)
=m>len(a$)
}
}
Locale 1033 ' to use . as decimal, else we have to place 1033 or "." as second parameter
Print isNumeric("+1"), isNumeric("-1"), isNumeric("1+")=false, isNumeric("1-")=false
Print isNumeric(",1",","), isNumeric("1,",","), isNumeric(",0",","), isNumeric("0,", ",")
Print isNumeric(".1"), isNumeric("1."), isNumeric(".0"), isNumeric("0.")
Print isNumeric("+.1"), isNumeric("-1."), isNumeric(".12e+232"), isNumeric("0.122e10")
Print isNumeric("+.1a")=false, isNumeric("asasa1212")=false, isNumeric("1.2e43+23")=false, isNumeric("0.122e10")
Print isNumeric("1221.211.1221")=false, isNumeric("1221e1212")=false, isNumeric("1.2e4323")=false, isNumeric("-.122e-10")
Maple
isNumeric := proc(s)
try
if type(parse(s), numeric) then
printf("The string is numeric."):
else
printf("The string is not numeric."):
end if:
catch:
printf("The string is not numeric."):
end try:
end proc:
=={{header|Mathematica}} / {{header|Wolfram Language}}==
NumberQ[ToExpression["02553352000242"]]
MATLAB
% copy from Octave version on this page
function r = isnum(a)
if ( isnumeric(a) )
r = 1;
else
o = str2num(a);
r = !isempty(o);
endif
end
% tests
disp(isnum(123)) % 1
disp(isnum("123")) % 1
disp(isnum("foo123")) % 0
disp(isnum("123bar")) % 0
disp(isnum("3.1415")) % 1
Maxima
numberp(parse_string("170141183460469231731687303715884105727"));
MAXScript
fn isNumeric str =
(
try
(
(str as integer) != undefined
)
catch(false)
)
isNumeric "123"
min
{{works with|min|0.19.3}}
(
dup (((int integer?) (pop false)) try) dip
((float float?) (pop false)) try or
) :numeric?
MiniScript
We rely on conversion to number returning a nonzero number, plus special checks for zero strings. Note that the val function is forgiving about additional characters ''after'' the number, so our function is too.
isNumeric = function(s)
return s == "0" or s == "-0" or val(s) != 0
end function
print isNumeric("0")
print isNumeric("42")
print isNumeric("-3.14157")
print isNumeric("5@*#!")
print isNumeric("spam")
{{out}}
1
1
1
1
0
MIPS Assembly
# $a0 char val
# $a1 address pointer
# $a2 PERIOD_HIT_FLAG
# $a3 HAS_DIGITS_FLAG
.data
### CHANGE THIS STRING TO TEST DIFFERENT ONES... ###
string: .asciiz "-.1236"
s_false: .asciiz "False"
s_true: .asciiz "True"
.text
main:
set_up: #test for 0th char == 45 or 46 or 48...57
la $a1,string
lb $a0,($a1)
beq $a0,45,loop # == '-'
beq $a0,46,loop # == '.'
blt $a0,48,exit_false # isn't below the ascii range for chars '0'...'9'
bgt $a0,57,exit_false # isn't above the ascii range for chars '0'...'9'
loop:
addi $a1,$a1,1
lb $a0,($a1)
beqz $a0,exit_true # test for \0 null char
beq $a0,46,period_test #test for a duplicate period
blt $a0,48,exit_false #test for
bgt $a0,57,exit_false
la $a3,1 #set the HAS_DIGITS flag. This line is only reached because the
# tests for period and - both jump back to start.
j loop
exit_true:
beqz $a3,exit_false
la $a0,s_true
la $v0,4
syscall
li $v0,10
syscall
exit_false:
la $a0,s_false
la $v0,4
syscall
li $v0,10
syscall
period_test:
beq $a2,1,exit_false
li $a2,1
j loop
Mirah
import java.text.NumberFormat
import java.text.ParsePosition
import java.util.Scanner
# this first example relies on catching an exception,
# which is bad style and poorly performing in Java
def is_numeric?(s:string)
begin
Double.parseDouble(s)
return true
rescue
return false
end
end
puts '123 is numeric' if is_numeric?('123')
puts '-123 is numeric' if is_numeric?('-123')
puts '123.1 is numeric' if is_numeric?('123.1')
puts 'nil is not numeric' unless is_numeric?(nil)
puts "'' is not numeric" unless is_numeric?('')
puts 'abc is not numeric' unless is_numeric?('abc')
puts '123- is not numeric' unless is_numeric?('123-')
puts '1.2.3 is not numeric' unless is_numeric?('1.2.3')
# check every element of the string
def is_numeric2?(s: string)
if (s == nil || s.isEmpty())
return false
end
if (!s.startsWith('-'))
if s.contains('-')
return false
end
end
0.upto(s.length()-1) do |x|
c = s.charAt(x)
if ((x == 0) && (c == '-'.charAt(0)))
# negative number
elsif (c == '.'.charAt(0))
if (s.indexOf('.', x) > -1)
return false # more than one period
end
elsif (!Character.isDigit(c))
return false
end
end
true
end
puts '123 is numeric' if is_numeric2?('123')
puts '-123 is numeric' if is_numeric2?('-123')
puts '123.1 is numeric' if is_numeric2?('123.1')
puts 'nil is not numeric' unless is_numeric2?(nil)
puts "'' is not numeric" unless is_numeric2?('')
puts 'abc is not numeric' unless is_numeric2?('abc')
puts '123- is not numeric' unless is_numeric2?('123-')
puts '1.2.3 is not numeric' unless is_numeric2?('1.2.3')
# use a regular expression
def is_numeric3?(s:string)
s == nil || s.matches("[-+]?\\d+(\\.\\d+)?")
end
puts '123 is numeric' if is_numeric3?('123')
puts '-123 is numeric' if is_numeric3?('-123')
puts '123.1 is numeric' if is_numeric3?('123.1')
puts 'nil is not numeric' unless is_numeric3?(nil)
puts "'' is not numeric" unless is_numeric3?('')
puts 'abc is not numeric' unless is_numeric3?('abc')
puts '123- is not numeric' unless is_numeric3?('123-')
puts '1.2.3 is not numeric' unless is_numeric3?('1.2.3')
# use the positional parser in the java.text.NumberFormat object
# (a more robust solution). If, after parsing, the parse position is at
# the end of the string, we can deduce that the entire string was a
# valid number.
def is_numeric4?(s:string)
return false if s == nil
formatter = NumberFormat.getInstance()
pos = ParsePosition.new(0)
formatter.parse(s, pos)
s.length() == pos.getIndex()
end
puts '123 is numeric' if is_numeric4?('123')
puts '-123 is numeric' if is_numeric4?('-123')
puts '123.1 is numeric' if is_numeric4?('123.1')
puts 'nil is not numeric' unless is_numeric4?(nil)
puts "'' is not numeric" unless is_numeric4?('')
puts 'abc is not numeric' unless is_numeric4?('abc')
puts '123- is not numeric' unless is_numeric4?('123-')
puts '1.2.3 is not numeric' unless is_numeric4?('1.2.3')
# use the java.util.Scanner object. Very useful if you have to
# scan multiple entries. Scanner also has similar methods for longs,
# shorts, bytes, doubles, floats, BigIntegers, and BigDecimals as well
# as methods for integral types where you may input a base/radix other than
# 10 (10 is the default, which can be changed using the useRadix method).
def is_numeric5?(s:string)
return false if s == nil
Scanner sc = Scanner.new(s)
sc.hasNextDouble()
end
puts '123 is numeric' if is_numeric5?('123')
puts '-123 is numeric' if is_numeric5?('-123')
puts '123.1 is numeric' if is_numeric5?('123.1')
puts 'nil is not numeric' unless is_numeric5?(nil)
puts "'' is not numeric" unless is_numeric5?('')
puts 'abc is not numeric' unless is_numeric5?('abc')
puts '123- is not numeric' unless is_numeric5?('123-')
puts '1.2.3 is not numeric' unless is_numeric5?('1.2.3')
mIRC Scripting Language
{{works with|mIRC}}
var %value = 3
if (%value isnum) {
echo -s %value is numeric.
}
=={{header|Modula-3}}==
MODULE Numeric EXPORTS Main;
IMPORT IO, Fmt, Text;
PROCEDURE isNumeric(s: TEXT): BOOLEAN =
BEGIN
FOR i := 0 TO Text.Length(s) DO
WITH char = Text.GetChar(s, i) DO
IF i = 0 AND char = '-' THEN
EXIT;
END;
IF char >= '0' AND char <= '9' THEN
EXIT;
END;
RETURN FALSE;
END;
END;
RETURN TRUE;
END isNumeric;
BEGIN
IO.Put("isNumeric(152) = " & Fmt.Bool(isNumeric("152")) & "\n");
IO.Put("isNumeric(-3.1415926) = " & Fmt.Bool(isNumeric("-3.1415926")) & "\n");
IO.Put("isNumeric(Foo123) = " & Fmt.Bool(isNumeric("Foo123")) & "\n");
END Numeric.
{{out}}
isNumeric(152) = TRUE
isNumeric(-3.1415926) = TRUE
isNumeric(Foo123) = FALSE
MUMPS
In MUMPS, strings are automatically converted to numbers when a unary or binary arithmetic operator works upon them. If there are no leading digits, a string converts to zero. If there a string of digits followed by an "e" or an "E" followed in turn by more digits, the numbers after the letter are treated as an exponent.
Examples from command line: ```txt
USER>WRITE +"1" 1 USER>WRITE +"1A" 1 USER>WRITE +"A1" 0 USER>WRITE +"1E" 1 USER>WRITE +"1E2" 100 USER>WRITE +"1EA24" 1 USER>WRITE +"1E3A" 1000 USER>WRITE +"1E-3" .001
</p>
<p>There is a function, $ISVALIDNUM, to do the testing.
```txt
USER>WRITE $SELECT($ISVALIDNUM("123"):"Valid",1:"Invalid"),!
Valid
USER>WRITE $SELECT($ISVALIDNUM("a123"):"Valid",1:"Invalid"),!
Invalid
USER>WRITE $SELECT($ISVALIDNUM("123a"):"Valid",1:"Invalid"),!
Invalid
USER>WRITE $SELECT($ISVALIDNUM("123e4"):"Valid",1:"Invalid"),!
Valid
Nemerle
using System;
using System.Console;
module IsNumeric
{
IsNumeric( input : string) : bool
{
mutable meh = 0.0; // I don't want it, not going to use it, why force me to declare it?
double.TryParse(input, out meh)
}
Main() : void
{
def num = "-1.2345E6";
def not = "abc45";
WriteLine($"$num is numeric: $(IsNumeric(num))");
WriteLine($"$not is numeric: $(IsNumeric(not))");
}
}
NetRexx
/* NetRexx */
options replace format comments java crossref symbols nobinary
numeric digits 20
loop n_ over getTestData()
-- could have used n_.datatype('N') directly here...
if isNumeric(n_) then msg = 'numeric'
else msg = 'not numeric'
say ('"'n_'"').right(25)':' msg
end n_
return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Pointless in NetRexx; the DATATYPE built-in-function is more powerful!
method isNumeric(testString) public static returns boolean
return testString.datatype('N')
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method getTestData() private static returns Rexx[]
-- Coercing numbers into the Rexx type has the effect of converting them to strings.
-- NetRexx will still perform arithmetic on Rexx strings if those strings represent numbers.
-- Notice that whitespace between the sign and the number are ignored even when inside a string constant
testData = [ Rexx -
' one and a half', 1, 1.5, 1.5e+27, ' 1 ', ' 1.5 ', ' 1.5e+27 ', -
'-one and a half', - 1, - 1.5, - 1.5e-27, ' - 1 ', '- 1.5 ', '- 1.5e-27 ', -
'+one and a half', + 1, + 1.5, + 1.5e+27, ' + 1 ', '+ 1.5 ', '+ 1.5e+27 ', -
'Math Constants', -
Math.PI, Math.E, -
-Math.PI, -Math.E, -
+Math.PI, +Math.E, -
'Numeric Constants', -
Double.NaN, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY -
]
return testData
{{out}}
" one and a half": not numeric
"1": numeric
"1.5": numeric
"1.5e+27": numeric
" 1 ": numeric
" 1.5 ": numeric
" 1.5e+27 ": numeric
"-one and a half": not numeric
"-1": numeric
"-1.5": numeric
"-1.5E-27": numeric
" - 1 ": numeric
"- 1.5 ": numeric
"- 1.5e-27 ": numeric
"+one and a half": not numeric
"1": numeric
"1.5": numeric
"1.5E+27": numeric
" + 1 ": numeric
"+ 1.5 ": numeric
"+ 1.5e+27 ": numeric
"Math Constants": not numeric
"3.141592653589793": numeric
"2.718281828459045": numeric
"-3.141592653589793": numeric
"-2.718281828459045": numeric
"3.141592653589793": numeric
"2.718281828459045": numeric
"Numeric Constants": not numeric
"NaN": not numeric
"Infinity": not numeric
"Infinity": not numeric
Nim
import strutils
let s = "123"
var f: float
try:
f = parseFloat s
except EInvalidValue:
echo "not numeric"
if s.contains AllChars - Digits:
echo "not a positive integer"
=={{header|Objective-C}}== {{works with|GCC}} {{works with|OpenStep}} {{works with|GNUstep}}
The ''NSScanner'' class supports scanning of strings for various types. The ''scanFloat'' method will return YES if the string is numeric, even if the number is actually too long to be contained by the precision of a ''float''.
if( [[NSScanner scannerWithString:@"-123.4e5"] scanFloat:NULL] )
NSLog( @"\"-123.4e5\" is numeric" );
else
NSLog( @"\"-123.4e5\" is not numeric" );
if( [[NSScanner scannerWithString:@"Not a number"] scanFloat:NULL] )
NSLog( @"\"Not a number\" is numeric" );
else
NSLog( @"\"Not a number\" is not numeric" );
// prints: "-123.4e5" is numeric
// prints: "Not a number" is not numeric
The following function can be used to check if a string is numeric "totally"; this is achieved by checking if the scanner reached the end of the string after the float is parsed.
BOOL isNumeric(NSString *s)
{
NSScanner *sc = [NSScanner scannerWithString: s];
if ( [sc scanFloat:NULL] )
{
return [sc isAtEnd];
}
return NO;
}
If we want to scan ''by hand'', we could use a function like the following, that checks if a number is an integer positive or negative number; spaces can appear at the beginning, but not after the number, and the '+' or '-' can appear only ''attached'' to the number ("+123" returns YES, but "+ 123" returns NO).
BOOL isNumericI(NSString *s)
{
NSUInteger len = [s length];
NSUInteger i;
BOOL status = NO;
for(i=0; i < len; i++)
{
unichar singlechar = [s characterAtIndex: i];
if ( (singlechar == ' ') && (!status) )
{
continue;
}
if ( ( singlechar == '+' ||
singlechar == '-' ) && (!status) ) { status=YES; continue; }
if ( ( singlechar >= '0' ) &&
( singlechar <= '9' ) )
{
status = YES;
} else {
return NO;
}
}
return (i == len) && status;
}
Here we assumed that in the internal encoding of a string (that should be Unicode), 1 comes after 0, 2 after 1 and so on until 9. Another way could be to get the C String from the NSString object, and then the parsing would be the same of the one we could do in standard C, so this path is not given.
OCaml
This function is not particularly useful in a statically typed language. Instead, one would just attempt to convert the string to the desired type and handle parsing failure appropriately.
The task doesn't define which strings are considered "numeric", so we do ints and floats, which should catch the most common cases:
let is_int s =
try ignore (int_of_string s); true
with _ -> false
let is_float s =
try ignore (float_of_string s); true
with _ -> false
let is_numeric s = is_int s || is_float s
Octave
The builtin function isnumeric return true (1) if the argument is a data of type ''number''; the provided function isnum works the same for numeric datatype, while if another type is passed as argument, it tries to convert it to a number; if the conversion fails, it means it is not a string representing a number.
function r = isnum(a)
if ( isnumeric(a) )
r = 1;
else
o = str2num(a);
r = !isempty(o);
endif
endfunction
% tests
disp(isnum(123)) % 1
disp(isnum("123")) % 1
disp(isnum("foo123")) % 0
disp(isnum("123bar")) % 0
disp(isnum("3.1415")) % 1
STR2NUM uses internally the function eval(), therefore it should not be used for unsecured data (e.g. user input). Use instead str2double() or scanf().
function r = isnum(a)
if ( isnumeric(a) )
r = 1;
else
o = str2double(a);
r = !isnan(o);
endif
endfunction
Oz
fun {IsNumeric S}
{String.isInt S} orelse {String.isFloat S}
end
PARI/GP
isNumeric(s)={
my(t=type(eval(s)));
t == "t_INT" || t == "T_REAL"
};
Pascal
See [[#Delphi|Delphi]] or [[#Free Pascal|Free Pascal]].
PeopleCode
Built-In Function
Syntax
IsNumber(Value)
Description
Use the IsNumber function to determine if Value contains a valid numeric value. Numeric characters include sign indicators and comma and period decimal points.
To determine if a value is a number and if it's in the user's local format, use the IsUserNumber function.
Parameters
Value
Specify a string you want to search to determine if it is a valid number.
Returns
A Boolean value: True if Value contains a valid numeric value, False otherwise.
Example
&Value = Get Field().Value;
If IsNumber(&Value) Then
/* do numeric processing */
Else
/* do non-numeric processing */
End-if;
Perl
{{works with|Perl|5.8}}
use Scalar::Util qw(looks_like_number);
print looks_like_number($str) ? "numeric" : "not numeric\n";
{{works with|Perl|5.8}} Quoting from [http://perldoc.perl.org/perlfaq4.html#How-do-I-determine-whether-a-scalar-is-a-number%2fwhole%2finteger%2ffloat%3f perlfaq4]:
''How do I determine whether a scalar is a number/whole/integer/float?''
Assuming that you don't care about [[IEEE]] notations like "NaN" or "Infinity", you probably just want to use a [[Regular expression matching|regular expression]].
if (/\D/) { print "has nondigits\n" }
if (/^\d+\z/) { print "is a whole number\n" }
if (/^-?\d+\z/) { print "is an integer\n" }
if (/^[+-]?\d+\z/) { print "is a +/- integer\n" }
if (/^-?\d+\.?\d*\z/) { print "is a real number\n" }
if (/^-?(?:\d+(?:\.\d*)?&\.\d+)\z/) { print "is a decimal number\n" }
if (/^([+-]?)(?=\d&\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?\z/)
{ print "a C float\n" }
There are also some commonly used modules for the task. Scalar::Util (distributed with 5.8) provides access to Perl's internal function "looks_like_number" for determining whether a variable looks like a number. Data::Types exports functions that validate data types using both the above and other regular expressions. Thirdly, there is "Regexp::Common" which has regular expressions to match various types of numbers. Those three modules are available from the CPAN.
If you're on a [[POSIX]] system, Perl supports the "POSIX::strtod" function. Its semantics are somewhat cumbersome, so here's a "getnum" wrapper function for more convenient access. This function takes a string and returns the number it found, or "undef" for input that isn't a C float. The "is_numeric" function is a front end to "getnum" if you just want to say, ''Is this a float?''
sub getnum {
use POSIX;
my $str = shift;
$str =~ s/^\s+//;
$str =~ s/\s+$//;
$! = 0;
my($num, $unparsed) = strtod($str);
if (($str eq '') && ($unparsed != 0) && $!) {
return undef;
} else {
return $num;
}
}
sub is_numeric { defined getnum($_[0]) }
Or you could check out the String::Scanf module on the CPAN instead. The POSIX module (part of the standard Perl distribution) provides the "strtod" and "strtol" for converting strings to double and longs, respectively.
Perl 6
{{works with|Rakudo|2017.11}} Perl 6 tries very hard to DWIM (do what I mean). As part of that, numeric strings are by default stored as allomorphic types which can be used as numbers or strings without any conversion. If we truly want to operate on strings, we have to explicitly coerce the allomorphs to strings. A subtlety that may not be immediately apparent, whitespace, empty strings and null strings may be treated as (False) boolean values in Perl 6, however booleans are allomorphic to numeric, so empty strings will coerce to a numeric value (0), and return as numeric unless specifically checked for.
Note: These routines are usable for most cases but won't detect unicode non-digit numeric forms; E.G. vulgar fractions, Roman numerals, circled numbers, etc. If it is necessary to detect those as numeric, a full fledged grammar may be necessary.
sub is-number-w-ws( Str $term --> Bool ) { # treat Falsey strings as numeric
$term.Numeric !~~ Failure;
}
sub is-number-wo-ws( Str $term --> Bool ) { # treat Falsey strings as non-numeric
?($term ~~ / \S /) && $term.Numeric !~~ Failure;
}
say " Coerce Don't coerce";
say ' String whitespace whitespace';
printf "%10s %8s %11s\n",
"<$_>", .&is-number-w-ws, .&is-number-wo-ws for
(|<1 1.2 1.2.3 -6 1/2 12e B17 1.3e+12 1.3e12 -2.6e-3 zero
0x 0xA10 0b1001 0o16 0o18 2+5i>, '1 1 1', '', ' ').map: *.Str;
Coerce Don't coerce
String whitespace whitespace
<1> True True
<1.2> True True
<1.2.3> False False
<-6> True True
<1/2> True True
<12e> False False
<B17> False False
<1.3e+12> True True
<1.3e12> True True
<-2.6e-3> True True
<zero> False False
<0x> False False
<0xA10> True True
<0b1001> True True
<0o16> True True
<0o18> False False
<2+5i> True True
<1 1 1> False False
<> True False
< > True False
Phix
function isNumber(string s)
return scanf(s,"%f")!={}
end function
test code
function testset(sequence s)
for i=1 to length(s) do
s[i] = isNumber(s[i])
end for
return s
end function
?testset({"#a","#A","0xA","0(16)A","#FF","255","0",".14",".05","-5.2","0xf","ten","1B"})
?testset({" 12 ",trim(" 12 ")})
?testset({"0o16","0o18"})
?testset({"1_000","0b10101111_11110000_11110000_00110011","-0b10101","0x10.5",""," ","1.","50e"})
{{out}}
{1,1,1,1,1,1,1,1,1,1,1,0,0}
{0,1}
{1,0}
{1,1,1,0,0,0,0,0}
PHP
<?php
$string = '123';
if(is_numeric(trim($string))) {
}
?>
PicoLisp
The '[http://software-lab.de/doc/refF.html#format format]' function can be used for that. It returns NIL if the given string is not a legal number
: (format "123")
-> 123
: (format "123a45")
-> NIL
: (format "-123.45" 4)
-> 1234500
Pike
the sscanf format %f will find any kind of number. the %s before and after make sure the number is not surrounded by other text.
int(0..1) is_number(string s)
{
array test = array_sscanf(s, "%s%f%s");
if (sizeof(test) == 3 && test[1] && !sizeof(test[0]) && !sizeof(test[2]) )
return true;
else
return false;
}
string num = "-1.234"
is_number(num);
-> true
PL/I
is_numeric: procedure (text) returns (bit (1));
declare text character (*);
declare x float;
on conversion go to done;
get string(text) edit (x) (E(length(text),0));
return ('1'b);
done:
return ('0'b);
end is_numeric;
5 '1'B
6.7 '1'B
-8.9 '1'B
-4e3 '1'B
4A37 '0'B
PL/SQL
FUNCTION IsNumeric( value IN VARCHAR2 )
RETURN BOOLEAN
IS
help NUMBER;
BEGIN
help := to_number( value );
return( TRUE );
EXCEPTION
WHEN others THEN
return( FALSE );
END;
Value VARCHAR2( 10 ) := '123';
IF( IsNumeric( Value ) )
THEN
NULL;
END IF;
PowerShell
Note: PowerShell 1.0 does not support 'try' THis simply tries arithmetic with the argument and if that fails, ''false'' is returned.
function isNumeric ($x) {
try {
0 + $x | Out-Null
return $true
} catch {
return $false
}
}
But this one doesn't work for strings like "8." though a . is appended it returns true!
Alternatively, you can use the static System.Int32.TryParse() method in the .NET framework.
function isNumeric ($x) {
$x2 = 0
$isNum = [System.Int32]::TryParse($x, [ref]$x2)
return $isNum
}
Prolog
{{works with|SWI-Prolog|7}}
The code:
numeric_string(String) :-
atom_string(Atom, String),
atom_number(Atom, _).
A predicate to test the code:
test_strings(Strings) :-
forall( member(String, Strings),
( ( numeric_string(String)
-> Result = a
; Result = 'not a' ),
format('~w is ~w number.~n', [String, Result])
)
).
Example of using the test predicate:
?- test_strings(["123", "0.123", "-123.1", "NotNum", "1."]).
123 is a number.
0.123 is a number.
-123.1 is a number.
NotNum is not a number.
1. is not a number.
true.
PureBasic
This routine parses the string to verify it's a number. It returns 1 if string is numeric, 0 if it is not. The character used as the decimal separator may be specified if desired.
Procedure IsNumeric(InString.s, DecimalCharacter.c = '.')
#NotNumeric = #False
#IsNumeric = #True
InString = Trim(InString)
Protected IsDecimal, CaughtDecimal, CaughtE
Protected IsSignPresent, IsSignAllowed = #True, CountNumeric
Protected *CurrentChar.Character = @InString
While *CurrentChar\c
Select *CurrentChar\c
Case '0' To '9'
CountNumeric + 1
IsSignAllowed = #False
Case DecimalCharacter
If CaughtDecimal Or CaughtE Or CountNumeric = 0
ProcedureReturn #NotNumeric
EndIf
CountNumeric = 0
CaughtDecimal = #True
IsDecimal = #True
Case '-', '+'
If IsSignPresent Or Not IsSignAllowed: ProcedureReturn #NotNumeric: EndIf
IsSignPresent = #True
Case 'E', 'e'
If CaughtE Or CountNumeric = 0
ProcedureReturn #NotNumeric
EndIf
CaughtE = #True
CountNumeric = 0
CaughtDecimal = #False
IsSignPresent = #False
IsSignAllowed = #True
Default
ProcedureReturn #NotNumeric
EndSelect
*CurrentChar + SizeOf(Character)
Wend
If CountNumeric = 0: ProcedureReturn #NotNumeric: EndIf
ProcedureReturn #IsNumeric
EndProcedure
If OpenConsole()
PrintN("'+3183.31151E+321' = " + Str(IsNumeric("+3183.31151E+321")))
PrintN("'-123456789' = " + Str(IsNumeric("-123456789")))
PrintN("'123.45.6789+' = " + Str(IsNumeric("123.45.6789+")))
PrintN("'-e' = " + Str(IsNumeric("-e")))
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit")
Input()
CloseConsole()
EndIf
{{out}}
'+3183.31151E+321' = 1
'-123456789' = 1
'123.45.6789+' = 0
'-e' = 0
Python
Python: Simple int/float
def is_numeric(s):
try:
float(s)
return True
except (ValueError, TypeError):
return False
is_numeric('123.0')
Or for positive integers only:
'123'.isdigit()
Python: Most numeric literals
Including complex, hex, binary, and octal numeric literals we get:
def is_numeric(literal):
"""Return whether a literal can be parsed as a numeric value"""
castings = [int, float, complex,
lambda s: int(s,2), #binary
lambda s: int(s,8), #octal
lambda s: int(s,16)] #hex
for cast in castings:
try:
cast(literal)
return True
except ValueError:
pass
return False
Sample use, including value parsed, its type, and standard method str.isnumeric():
def numeric(literal):
"""Return value of numeric literal or None if can't parse a value"""
castings = [int, float, complex,
lambda s: int(s,2), #binary
lambda s: int(s,8), #octal
lambda s: int(s,16)] #hex
for cast in castings:
try:
return cast(literal)
except ValueError:
pass
return None
tests = [
'0', '0.', '00', '123', '0123', '+123', '-123', '-123.', '-123e-4', '-.8E-04',
'0.123', '(5)', '-123+4.5j', '0b0101', ' +0B101 ', '0o123', '-0xABC', '0x1a1',
'12.5%', '1/2', '½', '3¼', 'π', 'Ⅻ', '1,000,000', '1 000', '- 001.20e+02',
'NaN', 'inf', '-Infinity']
for s in tests:
print("%14s -> %-14s %-20s is_numeric: %-5s str.isnumeric: %s" % (
'"'+s+'"', numeric(s), type(numeric(s)), is_numeric(s), s.isnumeric() ))
{{out}}
"0" -> 0 <class 'int'> is_numeric: True str.isnumeric: True
"0." -> 0.0 <class 'float'> is_numeric: True str.isnumeric: False
"00" -> 0 <class 'int'> is_numeric: True str.isnumeric: True
"123" -> 123 <class 'int'> is_numeric: True str.isnumeric: True
"0123" -> 123 <class 'int'> is_numeric: True str.isnumeric: True
"+123" -> 123 <class 'int'> is_numeric: True str.isnumeric: False
"-123" -> -123 <class 'int'> is_numeric: True str.isnumeric: False
"-123." -> -123.0 <class 'float'> is_numeric: True str.isnumeric: False
"-123e-4" -> -0.0123 <class 'float'> is_numeric: True str.isnumeric: False
"-.8E-04" -> -8e-05 <class 'float'> is_numeric: True str.isnumeric: False
"0.123" -> 0.123 <class 'float'> is_numeric: True str.isnumeric: False
"(5)" -> (5+0j) <class 'complex'> is_numeric: True str.isnumeric: False
"-123+4.5j" -> (-123+4.5j) <class 'complex'> is_numeric: True str.isnumeric: False
"0b0101" -> 5 <class 'int'> is_numeric: True str.isnumeric: False
" +0B101 " -> 5 <class 'int'> is_numeric: True str.isnumeric: False
"0o123" -> 83 <class 'int'> is_numeric: True str.isnumeric: False
"-0xABC" -> -2748 <class 'int'> is_numeric: True str.isnumeric: False
"0x1a1" -> 417 <class 'int'> is_numeric: True str.isnumeric: False
"12.5%" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False
"1/2" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False
"½" -> None <class 'NoneType'> is_numeric: False str.isnumeric: True
"3¼" -> None <class 'NoneType'> is_numeric: False str.isnumeric: True
"π" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False
"Ⅻ" -> None <class 'NoneType'> is_numeric: False str.isnumeric: True
"1,000,000" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False
"1 000" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False
"- 001.20e+02" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False
"NaN" -> nan <class 'float'> is_numeric: True str.isnumeric: False
"inf" -> inf <class 'float'> is_numeric: True str.isnumeric: False
"-Infinity" -> -inf <class 'float'> is_numeric: True str.isnumeric: False
R
strings <- c("152", "-3.1415926", "Foo123")
> suppressWarnings(!is.na(as.numeric(strings)))
[1] TRUE TRUE FALSE
RapidQ
isnumeric
$Typecheck on
Defint FALSE, TRUE
FALSE = 0
TRUE = NOT FALSE
Function isNumeric(s as string, optchar as string) as integer
If len(s) = 0 then
Result = FALSE
Exit Function
End If
if instr(s,"+") > 1 then
Result = FALSE
exit function
end if
if instr(s,"-") > 1 then
Result = FALSE
exit function
end if
Defint i, ndex = 0
For i = 1 to len(s)
select case asc(mid$(s,i,1))
case 43 '+
case 45 '-
case 46 '.
if ndex = 1 then
Result = FALSE
Exit function
end if
ndex = 1
case 48 to 57 '0 to 9
case else
if instr(optchar,(mid$(s,i,1))) = 0 then
Result = FALSE
exit function
end if
end select
next
Result = TRUE
End Function
'
### ======================================================
'Begin
'
### ======================================================
showmessage (str$(isNumeric("-152.34","")))
end
REBOL
REBOL [
Title: "Is Numeric?"
URL: http://rosettacode.org/wiki/IsNumeric
]
; Built-in.
numeric?: func [x][not error? try [to-decimal x]]
; Parse dialect for numbers.
sign: [0 1 "-"]
digit: charset "0123456789"
int: [some digit]
float: [int "." int]
number: [
sign float ["e" | "E"] sign int |
sign int ["e" | "E"] sign int |
sign float |
sign int
]
pnumeric?: func [x][parse x number]
; Test cases.
cases: parse {
10 -99
10.43 -12.04
1e99 1.0e10 -10e3 -9.12e7 2e-4 -3.4E-5
3phase Garkenhammer e n3v3r phase3
} none
foreach x cases [print [x numeric? x pnumeric? x]]
Retro
Retro does not have floating point numbers. For others, it provides '''isNumber?''':
"123" isNumber?
REXX
/*REXX program to determine if a string is numeric. */
yyy=' -123.78' /*or some such.*/
/*strings below are all numeric (REXX).*/
zzz=' -123.78 '
zzz='-123.78'
zzz='2'
zzz="2"
zzz=2
zzz='000000000004'
zzz='+5'
zzz=' +6 '
zzz=' + 7 '
zzz=' - 8 '
zzz=' - .9 '
zzz='- 19.'
zzz='.7'
zzz='2e3'
zzz=47e567
zzz='2e-3'
zzz='1.2e1'
zzz=' .2E6'
zzz=' 2.e5 '
zzz=' +1.2E0002 '
zzz=' +1.2e+002 '
zzz=' +0000001.200e+002 '
zzz=' - 000001.200e+002 '
zzz=' - 000008.201e-00000000000000002 '
ifx=i
/*Note: some REXX interpreters allow use of tab chars as blanks. */
/*all statements below are equivalent.*/
if \datatype(yyy,'n') then say 'oops, not numeric:' yyy
if \datatype(yyy,'N') then say 'oops, not numeric:' yyy
if ¬datatype(yyy,'N') then say 'oops, not numeric:' yyy
if ¬datatype(yyy,'numeric') then say 'oops, not numeric:' yyy
if ¬datatype(yyy,'nim.') then say 'oops, not numeric:' yyy
if datatype(yyy)\=='NUM' then say 'oops, not numeric:' yyy
if datatype(yyy)/=='NUM' then say 'oops, not numeric:' yyy
if datatype(yyy)¬=='NUM' then say 'oops, not numeric:' yyy
if datatype(yyy)¬= 'NUM' then say 'oops, not numeric:' yyy
/*note: REXX only looks at the first char for DATATYPE's 2nd arg. */
/*note: some REXX interpreters don't support the ¬ (not) character.*/
/*note: " " " " " the / as negation. */
Ring
see isdigit("0123456789") + nl + # print 1
isdigit("0123a") # print 0
Ruby
def is_numeric?(s)
begin
Float(s)
rescue
false # not numeric
else
true # numeric
end
end
or more compact:
def is_numeric?(s)
!!Float(s) rescue false
end
'''sample'''
strings = %w(0 0.0 -123 abc 0x10 0xABC 123a -123e3 0.1E-5 50e)
strings.each do |str|
puts "%9p => %s" % [str, is_numeric?(str)]
end
{{out}}
"0" => true
"0.0" => true
"-123" => true
"abc" => false
"0x10" => true
"0xABC" => true
"123a" => false
"-123e3" => true
"0.1E-5" => true
"50e" => false
Run BASIC
print isNumeric("123")
print isNumeric("1ab")
' ------------------------
' Numeric Check
' 0 = bad
' 1 = good
' ------------------------
FUNCTION isNumeric(f$)
isNumeric = 1
f$ = trim$(f$)
if left$(f$,1) = "-" or left$(f$,1) = "+" then f$ = mid$(f$,2)
for i = 1 to len(f$)
d$ = mid$(f$,i,1)
if d$ = "," then goto [nxtDigit]
if d$ = "." then
if dot$ = "." then isNumeric = 0
dot$ = "."
goto [nxtDigit]
end if
if (d$ < "0") or (d$ > "9") then isNumeric = 0
[nxtDigit]
next i
END FUNCTION
123 1
1ab 0
Rust
// This function is not limited to just numeric types but rather anything that implements the FromStr trait.
fn parsable<T: FromStr>(s: &str) -> bool {
s.parse::<T>().is_ok()
}
Scala
import scala.util.control.Exception.allCatch
def isNumber(s: String): Boolean = (allCatch opt s.toDouble).isDefined
def isNumeric(input: String): Boolean = input.forall(_.isDigit)
Or a more complete version, using a complex regular expression:
def isNumeric2(str: String): Boolean = {
str.matches(s"""[+-]?((\d+(e\d+)?[lL]?)|(((\d+(\.\d*)?)|(\.\d+))(e\d+)?[fF]?))""")
}
Or using the built-in number parsing and catching exceptions:
def isNumeric(str: String): Boolean = {
!throwsNumberFormatException(str.toLong) || !throwsNumberFormatException(str.toDouble)
}
def throwsNumberFormatException(f: => Any): Boolean = {
try { f; false } catch { case e: NumberFormatException => true }
}
Scheme
string->number returns #f when the string is not numeric and otherwise the number, which is non-#f and therefore true.
(define (numeric? s) (string->number s))
SQL PL
{{works with|Db2 LUW}} version 9.7 or higher. With SQL PL:
--#SET TERMINATOR @
CREATE OR REPLACE FUNCTION IS_NUMERIC (
IN STRING VARCHAR(10)
) RETURNS SMALLINT
-- ) RETURNS BOOLEAN
BEGIN
DECLARE RET SMALLINT;
-- DECLARE RET BOOLEAN;
DECLARE TMP INTEGER;
DECLARE CONTINUE HANDLER FOR SQLSTATE '22018'
SET RET = 1;
-- SET RET = FALSE;
SET RET = 0;
--SET RET = TRUE;
SET TMP = INTEGER(STRING);
RETURN RET;
END @
VALUES IS_NUMERIC('5')@
VALUES IS_NUMERIC('0')@
VALUES IS_NUMERIC('-1')@
VALUES IS_NUMERIC('A')@
VALUES IS_NUMERIC('-')@
VALUES IS_NUMERIC('z')@
VALUES IS_NUMERIC('')@
VALUES IS_NUMERIC(' ')@
Output:
db2 -td@
db2 => BEGIN
...
db2 (cont.) => END @
DB20000I The SQL command completed successfully.
VALUES IS_NUMERIC('5')
1
------
0
1 record(s) selected.
VALUES IS_NUMERIC('0')
1
------
0
1 record(s) selected.
VALUES IS_NUMERIC('-1')
1
------
0
1 record(s) selected.
VALUES IS_NUMERIC('A')
1
------
1
1 record(s) selected.
VALUES IS_NUMERIC('-')
1
------
1
1 record(s) selected.
VALUES IS_NUMERIC('z')
1
------
1
1 record(s) selected.
VALUES IS_NUMERIC('')
1
------
1
1 record(s) selected.
VALUES IS_NUMERIC(' ')
1
------
1
1 record(s) selected.
Racket
(define (string-numeric? s) (number? (string->number s)))
Or, since all non-#f are true:
(define string-numeric? string->number)
Seed7
The function isNumeric uses the function [http://seed7.sourceforge.net/libraries/scanstri.htm#getNumber%28inout_string%29 getNumber] from the library [http://seed7.sourceforge.net/libraries/scanstri.htm scanstri.s7i]. GetNumber reads a numeric literal from a string. The numeric literal is removed from the input string.
$ include "seed7_05.s7i";
include "scanstri.s7i";
const func boolean: isNumeric (in var string: stri) is func
result
var boolean: isNumeric is FALSE;
local
var string: numberStri is "";
begin
numberStri := getNumber(stri);
isNumeric := stri = "";
end func;
Sidef
There is the the ''String.looks_like_number'' method, which returns true when a given strings looks like a number:
say "0.1E-5".looks_like_number; #=> true
Alternatively, we can use regular expressions to determine this:
func is_numeric(s) {
(s ~~ /^[+-]?+(?=\.?[0-9])[0-9_]*+(?:\.[0-9_]++)?(?:[Ee](?:[+-]?+[0-9_]+))?\z/) ||
(s ~~ /^0(?:b[10_]*|x[0-9A-Fa-f_]*|[0-9_]+\b)\z/)
}
Sample:
var strings = %w(0 0.0 -123 abc 0x10 0xABC 123a -123e3 0.1E-5 50e);
for str in strings {
say ("%9s => %s" % (str, is_numeric(str)))
}
{{out}}
0 => true
0.0 => true
-123 => true
abc => false
0x10 => true
0xABC => true
123a => false
-123e3 => true
0.1E-5 => true
50e => false
Simula
Simula uses the '&' instead of 'e' or 'E' for the exponent part of a floating point decimal number.
BEGIN
BOOLEAN PROCEDURE ISNUMERIC(W); TEXT W;
BEGIN
BOOLEAN PROCEDURE MORE;
MORE := W.MORE;
CHARACTER PROCEDURE NEXT;
NEXT := IF MORE THEN W.GETCHAR ELSE CHAR(0);
CHARACTER PROCEDURE LAST;
LAST := IF W.LENGTH = 0
THEN CHAR(0)
ELSE W.SUB(W.LENGTH,1).GETCHAR;
CHARACTER CH;
W.SETPOS(1);
IF MORE THEN
BEGIN
CH := NEXT;
IF CH = '-' OR CH = '+' THEN CH := NEXT;
WHILE DIGIT(CH) DO CH := NEXT;
IF CH = '.' THEN
BEGIN
CH := NEXT;
IF NOT DIGIT(CH) THEN GOTO L;
WHILE DIGIT(CH) DO CH := NEXT;
END;
IF CH = '&' THEN
BEGIN
CH := NEXT;
IF CH = '-' OR CH = '+' THEN CH := NEXT;
WHILE DIGIT(CH) DO CH := NEXT;
END;
END;
L: ISNUMERIC := (W.LENGTH > 0) AND THEN (NOT MORE) AND THEN DIGIT(LAST);
END;
REAL X;
TEXT T;
FOR X := 0, -3.1415, 2.768&+31, 5&10, .5, 5.&10 DO
BEGIN
OUTREAL(X, 10, 20);
OUTIMAGE;
END;
OUTIMAGE;
FOR T :- "0", "-3.1415", "2.768&+31", ".5", "5&22" DO
BEGIN
OUTTEXT(IF ISNUMERIC(T) THEN " NUMERIC " ELSE "NOT NUMERIC ");
OUTCHAR('"');
OUTTEXT(T);
OUTCHAR('"');
IF T = "0" THEN OUTCHAR(CHAR(9)); OUTCHAR(CHAR(9));
COMMENT PROBE ;
X := T.GETREAL;
OUTREAL(X, 10, 20);
OUTIMAGE;
END;
OUTIMAGE;
X := 5.&10;
!X := 5&;
!X := 5.;
X := .5;
FOR T :- "", "5.", "5&", "5&+", "5.&", "5.&-", "5.&10" DO
BEGIN
OUTTEXT(IF ISNUMERIC(T) THEN " NUMERIC " ELSE "NOT NUMERIC ");
OUTCHAR('"');
OUTTEXT(T);
OUTCHAR('"');
OUTIMAGE;
END;
END
{{out}}
0.000000000&+000
-3.141500000&+000
2.768000000&+031
5.000000000&+010
5.000000000&-001
5.100000000&+000
NUMERIC "0" 0.000000000&+000
NUMERIC "-3.1415" -3.141500000&+000
NUMERIC "2.768&+31" 2.768000000&+031
NUMERIC ".5" 5.000000000&-001
NUMERIC "5&22" 5.000000000&+022
NOT NUMERIC ""
NOT NUMERIC "5."
NOT NUMERIC "5&"
NOT NUMERIC "5&+"
NOT NUMERIC "5.&"
NOT NUMERIC "5.&-"
NOT NUMERIC "5.&10"
Smalltalk
{{works with|GNU Smalltalk}}
The String class has the method isNumeric; this method (at least on version 3.0.4) does not recognize as number strings like '-123'! So I've written an extension...
String extend [
realIsNumeric [
(self first = $+) |
(self first = $-)
ifTrue: [
^ (self allButFirst) isNumeric
]
ifFalse: [
^ self isNumeric
]
]
]
{ '1234'. "true"
'3.14'. '+3.8111'. "true"
'+45'. "true"
'-3.78'. "true"
'-3.78.23'. "false"
'123e3' "false: the notation is not recognized"
} do: [ :a | a realIsNumeric printNl ]
{{works with|Smalltalk/X}} {{works with|GNU Smalltalk}} (should work with all)
(Number readFrom:(aString readStream) onError:[nil]) notNil
to handle radix numbers (such as 2r10111), use:
(Scanner scanNumberFrom:(aString readStream)) notNil
SNOBOL4
This task is easy in Snobol. Use the convert( ) function as a predicate returning success (T) or failure (F) for string to real conversion.
define('nchk(str)') :(nchk_end)
nchk convert(str,'real') :s(return)f(freturn)
nchk_end
* # Wrapper for testing
define('isnum(str)') :(isnum_end)
isnum isnum = 'F'; isnum = nchk(str) 'T'
isnum = isnum ': ' str :(return)
isnum_end
* # Test and display
output = isnum('123')
output = isnum('123.0')
output = isnum('123.')
output = isnum('-123')
output = isnum('3.14159')
output = isnum('1.2.3')
output = isnum('abc')
output = isnum('A440')
end
{{out}}
T: 123
T: 123.0
T: 123.
T: -123
T: 3.14159
F: 1.2.3
F: abc
F: A440
SQL
{{works with|MS SQL|Server 2005}}
declare @s varchar(10)
set @s = '1234.56'
print isnumeric(@s) --prints 1 if numeric, 0 if not.
if isnumeric(@s)=1 begin print 'Numeric' end
else print 'Non-numeric'
Standard ML
(* this function only recognizes integers in decimal format *)
fun isInteger s = case Int.scan StringCvt.DEC Substring.getc (Substring.full s) of
SOME (_,subs) => Substring.isEmpty subs
| NONE => false
fun isReal s = case Real.scan Substring.getc (Substring.full s) of
SOME (_,subs) => Substring.isEmpty subs
| NONE => false
fun isNumeric s = isInteger s orelse isReal s
Swift
{{works with|Swift|2.x+}}
func isNumeric(a: String) -> Bool {
return Double(a) != nil
}
{{works with|Swift|1.x}} This one only checks whether it is an integer:
func isNumeric(a: String) -> Bool {
return a.toInt() != nil
}
Tcl
if {
[string is double -strict $varname]
} then { ... }
Also string is integer (, string is alnum etc etc)
Toka
Returns a flag of TRUE if character-string parameter represents a signed or unsigned integer. Otherwise returns a flag of FALSE. The success or failure is dependent on the source is valid in the current numeric base. The '''>number''' function also recognizes several optional prefixes for overriding the current base during conversion.
[ ( string -- flag )
>number nip ] is isNumeric
( Some tests )
decimal
" 100" isNumeric . ( succeeds, 100 is a valid decimal integer )
" 100.21" isNumeric . ( fails, 100.21 is not an integer)
" a" isNumeric . ( fails, 'a' is not a valid integer in the decimal base )
" $a" isNumeric . ( succeeds, because $ is a valid override prefix )
( denoting that the following character is a hexadecimal number )
UNIX Shell
#!/bin/bash
isnum() {
printf "%f" $1 >/dev/null 2>&1
}
check() {
if isnum $1
then
echo "$1 is numeric"
else
echo "$1 is NOT numeric"
fi
}
check 2
check -3
check +45.44
check -33.332
check 33.aa
check 3.3.3
{{out}}
2 is numeric
-3 is numeric
+45.44 is numeric
-33.332 is numeric
33.aa is NOT numeric
3.3.3 is NOT numeric
Ursa
def isnum (string str)
try
double str
return true
catch valueerror
return false
end try
end isnum
VBA
In France, IsNumeric("123.45") return False. So we have to check the "." or "," and replace it by the Application.DecimalSeparator.
Sub Main()
Debug.Print Is_Numeric("")
Debug.Print Is_Numeric("-5.32")
Debug.Print Is_Numeric("-51,321 32")
Debug.Print Is_Numeric("123.4")
Debug.Print Is_Numeric("123,4")
Debug.Print Is_Numeric("123;4")
Debug.Print Is_Numeric("123.4x")
End Sub
Private Function Is_Numeric(s As String) As Boolean
Dim Separat As String, Other As String
Separat = Application.DecimalSeparator
Other = IIf(Separat = ",", ".", ",")
Is_Numeric = IsNumeric(Replace(s, Other, Separat))
End Function
VBScript
IsNumeric(Expr)
Returns a True if numeric and a false if not.
Vedit macro language
This routine returns TRUE if there is numeric value at current cursor location. Only signed and unsigned integers are recognized, in decimal, hex (preceded with 0x) or octal (preceded with 0o). Remove the SUPPRESS option to evaluate an expression instead of single numeric value.
:IS_NUMERIC:
if (Num_Eval(SUPPRESS)==0 && Cur_Char != '0') {
Return(FALSE)
} else {
Return(TRUE)
}
Visual Basic .NET
{{works with|Visual Basic .NET|2005}}
Dim Value As String = "+123"
If IsNumeric(Value) Then
PRINT "It is numeric."
End If
XLISP
The inbuilt function STRING->NUMBER returns the numeric value of a string if it can. We discard this value and return the Boolean value 'true'; otherwise, the IF conditional will not be satisfied and will return 'false'.
(DEFUN NUMERICP (X)
(IF (STRING->NUMBER X) T))
zkl
fcn isNum(text){
try{ text.toInt(); True }
catch{ try{ text.toFloat(); True }
catch{ False }
}
}
isNum("123.4") //-->True
isNum("123") //-->True
isNum("-123.4") //-->True
isNum("123.4x") //-->False
isNum("hoho") //-->False
isNum(123.4) //-->True
isNum(123) //-->True
{{omit from|GUISS}}
[[Category: String manipulation]]