⚠️ 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|Date and time}}
;Task: Determine whether a given year is a leap year in the Gregorian calendar.
;See also:
- [[wp:Leap year|Leap year (wiki)]]
360 Assembly
This is a callable subroutine to determine whether or not a given zoned-decimal 4-digit year is a Leap Year. Leap years are "evenly divisible" by 4, except those which end in '00' and are not evenly divisible by 400. The subroutine receives two parameters: (1) a 4-digit year (CCYY) (2) an 8-byte work area The value returned in Register 15 (by convention the "return code") indicates whether the year is a Leap Year: When R15 = zero, the year is a leap year. Otherwise it is not.
LPCK CSECT
USING LPCK,15
STM 0,12,20(13) STORE CALLER REGS
LM 1,2,0(1) R1 -> CCYY, R2 -> DOUBLE-WORD WORK AREA
PACK 0(8,2),0(4,1) PACK CCYY INTO WORK AREA
CVB 0,0(2) CONVERT TO BINARY (R0 = CCYY)
SRDL 0,32 R0|R1 = CCYY
LA 2,100 R2 = 100
DR 0,2 DIVIDE CCYY BY 100: R0 = YY, R1 = CC
LTR 0,0 YY = 0? IF CCYY DIV BY 100, LY IFF DIV BY 400
BZ A YES: R0|R1 = CC; CCYY DIV BY 100, TEST CC
SRDL 0,32 NO: R0|R1 = YY; CCYY NOT DIV BY 100, TEST YY
A LA 2,4 DIVISOR = 4; DIVIDEND = YY, OR DIV BY 100 CC
DR 0,2 DIVIDE BY 4: R0 = REMAINDER, R1 = QUOTIENT
LR 15,0 LOAD REMAINDER: IF 0, THEN LEAP YEAR
LM 0,12,20(13) RESTORE REGS
BR 14
END
Sample invocation from a COBOL program:
WORKING-STORAGE SECTION. 01 FILLER. 05 YEAR-VALUE PIC 9(4). 05 WKAREA PIC X(8).
PROCEDURE DIVISION.
MOVE 1936 TO YEAR-VALUE CALL 'LPCK' USING YEAR-VALUE, WKAREA PERFORM RESULT-DISPLAY MOVE 1900 TO YEAR-VALUE CALL 'LPCK' USING YEAR-VALUE, WKAREA PERFORM RESULT-DISPLAY GOBACK.
RESULT-DISPLAY.
IF RETURN-CODE = ZERO DISPLAY YEAR-VALUE ' IS A LEAP YEAR' ELSE DISPLAY YEAR-VALUE ' IS NOT A LEAP YEAR'.
68000 Assembly
;Example
move.l #2018,d0
bsr leap_year
addi.l #28,d1 ; # days in February 2018
rts
; Leap Year
;
; Input
; d0=year
;
; Output
; d1=1 if leap year, 0 if not leap year
; zero flag clear if leap year, set if not
;
leap_year:
cmpi.l #1752,d0
ble.s not_leap_year
move.l d0,d1
lsr.l #1,d1
bcs.s not_leap_year
lsr.l #1,d1
bcs.s not_leap_year
; If we got here, year is divisible by 4.
move.l d0,d1
divu #100,d1
swap d1
tst.w d1
bne.s is_leap_year
; If we got here, year is divisible by 100.
move.l d0,d1
divu #400,d1
swap d1
tst.w d1
bne.s not_leap_year
is_leap_year:
moveq.l #1,d1
rts
not_leap_year:
moveq.l #0,d1
rts
ActionScript
public function isLeapYear(year:int):Boolean { if (year % 100 == 0) { return (year % 400 == 0); } return (year % 4 == 0); }
Ada
-- Incomplete code, just a sniplet to do the task. Can be used in any package or method.
-- Adjust the type of Year if you use a different one.
function Is_Leap_Year (Year : Integer) return Boolean is
begin
if Year rem 100 = 0 then
return Year rem 400 = 0;
else
return Year rem 4 = 0;
end if;
end Is_Leap_Year;
-- An enhanced, more efficient version:
-- This version only does the 2 bit comparison (rem 4) if false.
-- It then checks rem 16 (a 4 bit comparison), and only if those are not
-- conclusive, calls rem 100, which is the most expensive operation.
-- I failed to be convinced of the accuracy of the algorithm at first,
-- so I rephrased it below.
-- FYI: 400 is evenly divisible by 16 whereas 100,200 and 300 are not. Ergo, the
-- set of integers evenly divisible by 16 and 100 are all evenly divisible by 400.
-- 1. If a year is not divisible by 4 => not a leap year. Skip other checks.
-- 2. If a year is evenly divisible by 16, it is either evenly divisible by 400 or
-- not evenly divisible by 100 => leap year. Skip further checks.
-- 3. If a year evenly divisible by 100 => not a leap year.
-- 4. Otherwise a leap year.
function Is_Leap_Year (Year : Integer) return Boolean is
begin
return (Year rem 4 = 0) and then ((Year rem 16 = 0) or else (Year rem 100 /= 0));
end Is_Leap_Year;
-- To improve speed a bit more, use with
pragma Inline (Is_Leap_Year);
ALGOL 68
{{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 '''format''ted transput}}
MODE YEAR = INT, MONTH = INT, DAY = INT;
PROC year days = (YEAR year)DAY: # Ignore 1752 CE for the moment #
( month days(year, 2) = 28 | 365 | 366 );
PROC month days = (YEAR year, MONTH month) DAY:
( month | 31,
28 + ABS (year MOD 4 = 0 AND year MOD 100 /= 0 OR year MOD 400 = 0),
31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
PROC is leap year = (YEAR year)BOOL: year days(year)=366;
test:(
[]INT test cases = (1900, 1994, 1996, 1997, 2000);
FOR i TO UPB test cases DO
YEAR year = test cases[i];
printf(($g(0)" is "b("","not ")"a leap year."l$, year, is leap year(year)))
OD
)
{{out}}
1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
=={{header|Algol-M}}==
BEGIN
% COMPUTE P MOD Q %
INTEGER FUNCTION MOD(P, Q);
INTEGER P, Q;
BEGIN
MOD := P - Q * (P / Q);
END;
% RETURN NON-ZERO IF Y IS A LEAP YEAR %
INTEGER FUNCTION ISLEAP(Y);
INTEGER Y;
BEGIN
IF MOD(Y,4) <> 0 THEN % QUICK EXIT IN MOST CASES %
ISLEAP := 0
ELSE IF MOD(Y,400) = 0 THEN
ISLEAP := 1
ELSE IF MOD(Y,100) = 0 THEN
ISLEAP := 0
ELSE % NON-CENTURY DIVISIBLE BY 4 %
ISLEAP := 1;
END;
% EXERCISE THE FUNCTION %
INTEGER Y;
WRITE("TEST OF CENTURY YEARS");
FOR Y := 1600 STEP 100 UNTIL 2000 DO
BEGIN
IF ISLEAP(Y) <> 0 THEN
WRITE(Y, " IS A LEAP YEAR")
ELSE
WRITE(Y, " IS NOT A LEAP YEAR");
END;
WRITE("TEST OF CURRENT DECADE");
FOR Y := 2010 STEP 1 UNTIL 2020 DO
BEGIN
IF ISLEAP(Y) <> 0 THEN
WRITE(Y, " IS A LEAP YEAR")
ELSE
WRITE(Y, " IS NOT A LEAP YEAR");
END;
END
{{out}}
TEST OF CENTURY YEARS
1600 IS A LEAP YEAR
1700 IS NOT A LEAP YEAR
1800 IS NOT A LEAP YEAR
1900 IS NOT A LEAP YEAR
2000 IS A LEAP YEAR
TEST OF CURRENT DECADE
2010 IS NOT A LEAP YEAR
2011 IS NOT A LEAP YEAR
2012 IS A LEAP YEAR
2013 IS NOT A LEAP YEAR
2014 IS NOT A LEAP YEAR
2015 IS NOT A LEAP YEAR
2016 IS A LEAP YEAR
2017 IS NOT A LEAP YEAR
2018 IS NOT A LEAP YEAR
2019 IS NOT A LEAP YEAR
2020 IS A LEAP YEAR
ALGOL W
begin
% returns true if year is a leap year, false otherwise %
% assumes year is in the Gregorian Calendar %
logical procedure isLeapYear ( integer value year ) ;
year rem 400 = 0 or ( year rem 4 = 0 and year rem 100 not = 0 );
% some test cases %
for year := 1899, 1900, 1901, 1902, 1903, 1904, 1905, 1999, 2000, 2001, 2002, 2003, 2004 do begin
write( i_w := 1, s_w := 0
, year
, " is "
, if isLeapYear( year ) then "" else "not "
, " a leap year"
)
end for_year
end.
APL
⍝returns 1 if leapyear, 0 otherwise:
∇Z←LEAPYEAR YEAR
Z←(0=4|YEAR)∧(0=400|YEAR)∨~0=100|YEAR
∇
AppleScript
on leap_year(y) return year mod 4 is equal to 0 and (year mod 100 is not equal to 0 or year mod 400 is equal to 0) end leap_year leap_year(1900)
Arc
(= leap? (fn (year)
(if (and (is 0 (mod year 4)) (isnt 0 (mod year 100))) year
(unless (< 0 (+ (mod year 100) (mod year 400))) year))))
Output:
(map [leap? _] '(1900 1904 2000 2019 2020 2100))
;; => '( 1904 2000 2020 )
AutoHotkey
leapyear(year)
{
if (Mod(year, 100) = 0)
return (Mod(year, 400) = 0)
return (Mod(year, 4) = 0)
}
MsgBox, % leapyear(1604)
{{out}}
Returns 1 if year is a leap year
or
IsLeapYear(Year)
{
return !Mod(Year, 4) && Mod(Year, 100) || !Mod(Year, 400)
}
MsgBox % "The year 1604 was " (IsLeapYear(1604) ? "" : "not ") "a leap year"
{{out}}
The year 1600 was a leap year
The year 1601 was not a leap year
The year 1604 was a leap year
AutoIt
; AutoIt Version: 3.3.8.1
$Year = 2012
$sNot = " not"
If IsLeapYear($Year) Then $sNot = ""
ConsoleWrite ($Year & " is" & $sNot & " a leap year." & @LF)
Func IsLeapYear($_year)
Return Not Mod($_year, 4) And (Mod($_year, 100) Or Not Mod($_year, 400))
EndFunc
; == But it exists the standard UDF "Date.au3" with this function: "_IsLeapYear($Year)"
{{out}}
2012 is a leap year.
--[[User:BugFix|BugFix]] ([[User talk:BugFix|talk]]) 16:18, 16 November 2013 (UTC)
AWK
function leapyear( year )
{
if ( year % 100 == 0 )
return ( year % 400 == 0 )
else
return ( year % 4 == 0 )
}
Bash
#!/bin/bash
year=$(date +"%Y")
if (( $year % 4 == 0 ))
then
if (( $year % 400 == 0 ))
then
echo "This is a leap year"
else
if (( $year % 100 == 0 ))
then
echo "This is not a leap year"
else
echo "This is a leap year"
fi
fi
else
echo "This is not a leap year"
fi
BASIC
{{works with|QBasic}}
Note that the year%
function is not needed for most modern BASICs.
DECLARE FUNCTION diy% (y AS INTEGER)
DECLARE FUNCTION isLeapYear% (yr AS INTEGER)
DECLARE FUNCTION year% (date AS STRING)
PRINT isLeapYear(year(DATE$))
FUNCTION diy% (y AS INTEGER)
IF y MOD 4 THEN
diy = 365
ELSEIF y MOD 100 THEN
diy = 366
ELSEIF y MOD 400 THEN
diy = 365
ELSE
diy = 366
END IF
END FUNCTION
FUNCTION isLeapYear% (yr AS INTEGER)
isLeapYear = (366 = diy(yr))
END FUNCTION
FUNCTION year% (date AS STRING)
year% = VAL(RIGHT$(date, 4))
END FUNCTION
An old-timey solution:
{{works with|Commodore BASIC}}
10 DEF FNLY(Y)=(Y/4=INT(Y/4))*((Y/100<>INT(Y/100))+(Y/400=INT(Y/400)))
==={{header|IS-BASIC}}===
=
## Sinclair ZX81 BASIC
=
ZX81 BASIC does not support user-defined functions, even the single-expression functions that are provided by many contemporary dialects; so we have to fake it using a subroutine and pass everything in global variables.
```basic
5000 LET L=Y/4=INT (Y/4) AND (Y/100<>INT (Y/100) OR Y/400=INT (Y/400))
5010 RETURN
An example showing how to call it:
10 INPUT Y
20 GOSUB 5000
30 PRINT Y;" IS ";
40 IF NOT L THEN PRINT "NOT ";
50 PRINT "A LEAP YEAR."
60 STOP
=
ZX Spectrum Basic
=
10 DEF FN l(y)=y/4=INT (y/4) AND y/100<>INT (y/100) OR y/400=INT (y/400)
=
BaCon
= From the Ada shortcut calculation
' Leap year
FUNCTION leapyear(NUMBER y) TYPE NUMBER
RETURN IIF(MOD(y, 4) = 0, IIF(MOD(y, 16) = 0, IIF(MOD(y, 100) != 0, TRUE, FALSE), TRUE), FALSE)
END FUNCTION
READ y
WHILE y != 0
PRINT y, ": ", IIF$(leapyear(y), "", "not a "), "leapyear"
READ y
WEND
DATA 1600, 1700, 1800, 1900, 1901, 1996, 2000, 2001, 2004, 0
{{out}}
1600: not a leapyear
1700: leapyear
1800: leapyear
1900: leapyear
1901: not a leapyear
1996: leapyear
2000: not a leapyear
2001: not a leapyear
2004: leapyear
Batch File
@echo off
::The Main Thing...
for %%x in (1900 2046 2012 1600 1800 2031 1952) do (
call :leap %%x
)
echo.
pause
exit/b
::/The Main Thing...
::The Function...
:leap
set year=%1
set /a op1=%year%%%4
set /a op2=%year%%%100
set /a op3=%year%%%400
if not "%op1%"=="0" (goto :no)
if not "%op2%"=="0" (goto :yes)
if not "%op3%"=="0" (goto :no)
:yes
echo.
echo %year% is a leap year.
goto :EOF
:no
echo.
echo %year% is NOT a leap year.
goto :EOF
::/The Function...
{{out}}
1900 is NOT a leap year.
2046 is NOT a leap year.
2012 is a leap year.
1600 is a leap year.
1800 is NOT a leap year.
2031 is NOT a leap year.
1952 is a leap year.
Press any key to continue . . .
BBC BASIC
REPEAT
INPUT "Enter a year: " year%
IF FNleap(year%) THEN
PRINT ;year% " is a leap year"
ELSE
PRINT ;year% " is not a leap year"
ENDIF
UNTIL FALSE
END
DEF FNleap(yr%)
= (yr% MOD 4 = 0) AND ((yr% MOD 400 = 0) OR (yr% MOD 100 <> 0))
Befunge
{{trans|C}}
0"2("*:3-:1-:2-:"^"-v<
v*%"d"\!%4::,,"is".:<|
>\45*:*%!+#v_ "ton"vv<
v"ear."+550<,,,,*84<$#
>"y pael a ">:#,_$:#@^
{{out}}
1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
Bracmat
( leap-year
=
. mod$(!arg.100):0
& `(mod$(!arg.400):0) { The backtick skips the remainder of the OR operation,
even if the tested condition fails. }
| mod$(!arg.4):0
)
& 1600 1700 1899 1900 2000 2006 2012:?tests
& whl
' ( !tests:%?test ?tests
& ( leap-year$!test&out$(!test " is a leap year")
| out$(!test " is not a leap year")
)
)
& ;
{{out}}
1600 is a leap year
1700 is not a leap year
1899 is not a leap year
1900 is not a leap year
2000 is a leap year
2006 is not a leap year
2012 is a leap year
C
#include <stdio.h> int is_leap_year(int year) { return (!(year % 4) && year % 100 || !(year % 400)) ? 1 : 0; } int main() { int test_case[] = {1900, 1994, 1996, 1997, 2000}, key, end, year; for (key = 0, end = sizeof(test_case)/sizeof(test_case[0]); key < end; ++key) { year = test_case[key]; printf("%d is %sa leap year.\n", year, (is_leap_year(year) == 1 ? "" : "not ")); } }
{{out}}
1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
C++
Uses C++11. Compile with g++ -std=c++11 leap_year.cpp
#include <iostream> bool is_leap_year(int year) { return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0); } int main() { for (auto year : {1900, 1994, 1996, 1997, 2000}) { std::cout << year << (is_leap_year(year) ? " is" : " is not") << " a leap year.\n"; } }
{{out}}
1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
C#
using System; class Program { static void Main() { foreach (var year in new[] { 1900, 1994, 1996, DateTime.Now.Year }) { Console.WriteLine("{0} is {1}a leap year.", year, DateTime.IsLeapYear(year) ? string.Empty : "not "); } } }
{{out}}
1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
2010 is not a leap year.
Clipper
Function IsLeapYear( nYear )
Return Iif( nYear%100 == 0, (nYear%400 == 0), (nYear%4 == 0) )
Clojure
(defn leap-year? [y] (and (zero? (mod y 4)) (or (pos? (mod y 100)) (zero? (mod y 400)))))
COBOL
IDENTIFICATION DIVISION.
PROGRAM-ID. leap-year.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 examples VALUE "19001994199619972000".
03 year PIC 9(4) OCCURS 5 TIMES
INDEXED BY year-index.
01 remainders.
03 400-rem PIC 9(4).
03 100-rem PIC 9(4).
03 4-rem PIC 9(4).
PROCEDURE DIVISION.
PERFORM VARYING year-index FROM 1 BY 1 UNTIL 5 < year-index
MOVE FUNCTION MOD(year (year-index), 400) TO 400-rem
MOVE FUNCTION MOD(year (year-index), 100) TO 100-rem
MOVE FUNCTION MOD(year (year-index), 4) TO 4-rem
IF 400-rem = 0 OR ((100-rem NOT = 0) AND 4-rem = 0)
DISPLAY year (year-index) " is a leap year."
ELSE
DISPLAY year (year-index) " is not a leap year."
END-IF
END-PERFORM
GOBACK
.
Using Date Intrinsic Functions
program-id. leap-yr.
*> Given a year, where 1601 <= year <= 9999
*> Determine if the year is a leap year
data division.
working-storage section.
1 input-year pic 9999.
1 binary.
2 int-date pic 9(8).
2 cal-mo-day pic 9(4).
procedure division.
display "Enter calendar year (1601 thru 9999): "
with no advancing
accept input-year
if input-year >= 1601 and <= 9999
then
*> if the 60th day of a year is Feb 29
*> then the year is a leap year
compute int-date = function integer-of-day
( input-year * 1000 + 60 )
compute cal-mo-day = function mod (
(function date-of-integer ( int-date )) 10000 )
display "Year " input-year space with no advancing
if cal-mo-day = 229
display "is a leap year"
else
display "is NOT a leap year"
end-if
else
display "Input date is not within range"
end-if
stop run
.
end program leap-yr.
{{out}}
Enter calendar year (1601 thru 9999): 2016
Year 2016 is a leap year
Enter calendar year (1601 thru 9999): 2017
Year 2017 is NOT a leap year
Enter calendar year (1601 thru 9999): 2100
Year 2100 is NOT a leap year
Enter calendar year (1601 thru 9999): 2400
Year 2400 is a leap year
Enter calendar year (1601 thru 9999): 3000
Year 3000 is NOT a leap year
Enter calendar year (1601 thru 9999): 4000
Year 4000 is a leap year
Common Lisp
(defun leap-year-p (year) (destructuring-bind (fh h f) (mapcar #'(lambda (n) (zerop (mod year n))) '(400 100 4)) (or fh (and (not h) f))))
Component Pascal
BlackBox Component Builder
MODULE LeapYear;
IMPORT StdLog, Strings, Args;
PROCEDURE IsLeapYear(year: INTEGER): BOOLEAN;
BEGIN
IF year MOD 4 # 0 THEN
RETURN FALSE
ELSE
IF year MOD 100 = 0 THEN
IF year MOD 400 = 0 THEN RETURN TRUE ELSE RETURN FALSE END
ELSE
RETURN TRUE
END
END
END IsLeapYear;
PROCEDURE Do*;
VAR
p: Args.Params;
year,done,i: INTEGER;
BEGIN
Args.Get(p);
FOR i := 0 TO p.argc - 1 DO
Strings.StringToInt(p.args[i],year,done);
StdLog.Int(year);StdLog.String(":>");StdLog.Bool(IsLeapYear(year));StdLog.Ln
END;
END Do;
END LeapYear.
Execute: ^Q LeapYear.Do 2000 2004 2013~
{{out}}
2000:> $TRUE
2004:> $TRUE
2013:> $FALSE
D
import std.algorithm; bool leapYear(in uint y) pure nothrow { return (y % 4) == 0 && (y % 100 || (y % 400) == 0); } void main() { auto good = [1600, 1660, 1724, 1788, 1848, 1912, 1972, 2032, 2092, 2156, 2220, 2280, 2344, 2348]; auto bad = [1698, 1699, 1700, 1750, 1800, 1810, 1900, 1901, 1973, 2100, 2107, 2200, 2203, 2289]; assert(filter!leapYear(bad ~ good).equal(good)); }
Using the datetime library:
import std.datetime; void main() { assert(yearIsLeapYear(1724)); assert(!yearIsLeapYear(1973)); assert(!Date(1900, 1, 1).isLeapYear); assert(DateTime(2000, 1, 1).isLeapYear); }
Dart
class Leap { bool leapYear(num year) { return (year % 400 == 0) || (( year % 100 != 0) && (year % 4 == 0)); } }
=={{header|Delphi}}/{{header|Pascal}}== Delphi has standard function IsLeapYear in SysUtils unit.
program TestLeapYear;
{$APPTYPE CONSOLE}
uses
SysUtils;
var
Year: Integer;
begin
Write('Enter the year: ');
Readln(Year);
if IsLeapYear(Year) then
Writeln(Year, ' is a Leap year')
else
Writeln(Year, ' is not a Leap year');
Readln;
end.
DWScript
function IsLeapYear(y : Integer) : Boolean;
begin
Result:= (y mod 4 = 0)
and ( ((y mod 100) <> 0)
or ((y mod 400) = 0) );
end;
const good : array [0..13] of Integer =
[1600,1660,1724,1788,1848,1912,1972,2032,2092,2156,2220,2280,2344,2348];
const bad : array [0..13] of Integer =
[1698,1699,1700,1750,1800,1810,1900,1901,1973,2100,2107,2200,2203,2289];
var i : Integer;
PrintLn('Checking leap years');
for i in good do
if not IsLeapYear(i) then PrintLn(i);
PrintLn('Checking non-leap years');
for i in bad do
if IsLeapYear(i) then PrintLn(i);
Dyalect
func isLeap(y) {
if y % 100 == 0 {
y % 400 == 0
} else {
y % 4 == 0
}
}
print(isLeap(1984))
{{out}}
true
Ela
isLeap y | y % 100 == 0 = y % 400 == 0
| else = y % 4 == 0
Elixir
leap_year? = fn(year) -> :calendar.is_leap_year(year) end IO.inspect for y <- 2000..2020, leap_year?.(y), do: y
{{out}}
[2000, 2004, 2008, 2012, 2016, 2020]
Emacs Lisp
{{trans|Scheme}}
(defun leap-year-p (year) (apply (lambda (a b c) (or a (and (not b) c))) (mapcar (lambda (n) (zerop (mod year n))) '(400 100 4))))
Erlang
-module(gregorian). -export([leap/1]). leap( Year ) -> calendar:is_leap_year( Year ).
ERRE
PROGRAM LEAP_YEAR
FUNCTION LEAP(YR%)
LEAP=(YR% MOD 4=0) AND ((YR% MOD 400=0) OR (YR% MOD 100<>0))
END FUNCTION
BEGIN
LOOP
INPUT("Enter a year: ",year%)
EXIT IF YEAR%=0
IF LEAP(year%) THEN
PRINT(year%;" is a leap year")
ELSE
PRINT(year%;" is not a leap year")
END IF
END LOOP
END PROGRAM
Euphoria
function isLeapYear(integer year)
return remainder(year,4)=0 and remainder(year,100)!=0 or remainder(year,400)=0
end function
Excel
Take two cells, say A1 and B1, in B1 type in :
=IF(OR(NOT(MOD(A1,400)),AND(NOT(MOD(A1,4)),MOD(A1,100))),"Leap Year","Not a Leap Year")
{{out}}
1900 Not a Leap Year
1954 Not a Leap Year
1996 Leap Year
2003 Not a Leap Year
2012 Leap Year
=={{header|F_Sharp|F#}}==
let isLeapYear = System.DateTime.IsLeapYear assert isLeapYear 1996 assert isLeapYear 2000 assert not (isLeapYear 2001) assert not (isLeapYear 1900)
Factor
Call ''leap-year?'' word from ''calendars'' vocabulary. For example:
USING: calendar prettyprint ;
2011 leap-year? .
Factor uses proleptic Gregorian calendar.
Forth
: leap-year? ( y -- ? )
dup 400 mod 0= if drop true exit then
dup 100 mod 0= if drop false exit then
4 mod 0= ;
Or more simply (but always computing three "mod"):
: leap-year? dup 4 mod 0= over 16 mod 0= rot 25 mod 0= not or and ;
Fortran
program leap
implicit none
write(*,*) leap_year([1900, 1996, 1997, 2000])
contains
pure elemental function leap_year(y) result(is_leap)
implicit none
logical :: is_leap
integer,intent(in) :: y
is_leap = (mod(y,4)==0 .and. .not. mod(y,100)==0) .or. (mod(y,400)==0)
end function leap_year
end program leap
{{out}}
F T F T
FreeBASIC
' version 23-06-2015
' compile with: fbc -s console
#Ifndef TRUE ' define true and false for older freebasic versions
#Define FALSE 0
#Define TRUE Not FALSE
#EndIf
Function leapyear(Year_ As Integer) As Integer
If (Year_ Mod 4) <> 0 Then Return FALSE
If (Year_ Mod 100) = 0 AndAlso (Year_ Mod 400) <> 0 Then Return FALSE
Return TRUE
End Function
' ------=< MAIN >=------
' year is a FreeBASIC keyword
Dim As Integer Year_
For Year_ = 1800 To 2900 Step 100
Print Year_; IIf(leapyear(Year_), " is a leap year", " is not a leap year")
Next
Print : Print
For Year_ = 2012 To 2031
Print Year_;
If leapyear(Year_) = TRUE Then
Print " = leap",
Else
Print " = no",
End If
If year_ Mod 4 = 3 Then Print ' lf/cr
Next
' empty keyboard buffer
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End
{{out}}
1800 is not a leap year
1900 is not a leap year
2000 is a leap year
2100 is not a leap year
2200 is not a leap year
2300 is not a leap year
2400 is a leap year
2500 is not a leap year
2600 is not a leap year
2700 is not a leap year
2800 is a leap year
2900 is not a leap year
2012 = leap 2013 = no 2014 = no 2015 = no
2016 = leap 2017 = no 2018 = no 2019 = no
2020 = leap 2021 = no 2022 = no 2023 = no
2024 = leap 2025 = no 2026 = no 2027 = no
2028 = leap 2029 = no 2030 = no 2031 = no
FutureBasic
include "ConsoleWindow"
// In-line C function to generate random number in range
BeginCFunction
long randomInRange( long min, long max ) {
int i = (arc4random()%(max-min+1))+min;
return (long)i;
}
EndC
toolbox fn randomInRange( long min, long max ) = long
// Leap year test function
local fn LeapYear( year as long ) as Boolean
dim as Boolean result : result = _false
if year mod 400 == 0 then result = _true : exit fn
if year mod 100 == 0 then result = _false : exit fn
if year mod 4 == 0 then result = _true : exit fn
if year mod 4 != 0 then result = _false : exit fn
end fn = result
dim as long i, y, knownLeapYear(10)
// Array of known leap years from 1980 through 2020 for control
knownLeapYear(0) = 1980 : knownLeapYear(1) = 1984 : knownLeapYear(2) = 1988
knownLeapYear(3) = 1992 : knownLeapYear(4) = 1996 : knownLeapYear(5) = 2000
knownLeapYear(6) = 2004 : knownLeapYear(7) = 2008 : knownLeapYear(8) = 2012
knownLeapYear(9) = 2016 : knownLeapYear(10) = 2020
print "Known leap years:"
for i = 0 to 9
if ( fn LeapYear( knownLeapYear(i) ) == _true )
print knownLeapYear(i); " is a leap year."
else
print knownLeapYear(i); " is a not leap year."
end if
next
print
// Random years from 1980 to 2020 to test
print "Check random years:"
for i = 0 to 20
y = fn randomInRange( 1980, 2020 )
if ( fn LeapYear( y ) == _true )
print y; " is a leap year."
else
print y; " is a not leap year."
end if
next
Output (results will vary for random years):
Known leap years:
1980 is a leap year.
1984 is a leap year.
1988 is a leap year.
1992 is a leap year.
1996 is a leap year.
2000 is a leap year.
2004 is a leap year.
2008 is a leap year.
2012 is a leap year.
2016 is a leap year.
Check random years:
1998 is a not leap year.
1987 is a not leap year.
2015 is a not leap year.
1998 is a not leap year.
2020 is a leap year.
2020 is a leap year.
2009 is a not leap year.
2020 is a leap year.
2018 is a not leap year.
2013 is a not leap year.
2003 is a not leap year.
1994 is a not leap year.
1989 is a not leap year.
1999 is a not leap year.
1984 is a leap year.
1980 is a leap year.
1998 is a not leap year.
2008 is a leap year.
1983 is a not leap year.
2007 is a not leap year.
2004 is a leap year.
Gambas
Public Sub Form_Open()
Dim dDate As Date
Dim siYear As Short = InputBox("Enter a year", "Leap year test")
Dim sMessage As String = " is a leap year."
Try dDate = Date(siYear, 02, 29)
If Error Then sMessage = " is not a leap year."
Message(siYear & sMessage)
End
Output:
2016 is a leap year.
GAP
IsLeapYear := function(n)
return (n mod 4 = 0) and ((n mod 100 <> 0) or (n mod 400 = 0));
end;
# alternative using built-in function
IsLeapYear := function(n)
return DaysInYear(n) = 366;
end;
Genie
Dialect conversion from Vala entry.
[indent=4]
/*
Leap year, in Genie
valac leapYear.gs
./leapYear
*/
init
years:array of DateYear = {1900, 1994, 1996, 1997, 2000, 2100}
for year in years
status:string = year.is_leap_year() ? "" : "not "
stdout.printf("%d is %sa leap year.\n", year, status)
{{out}}
prompt$ valac leapYear.gs
prompt$ ./leapYear
1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
2100 is not a leap year.
Go
func isLeap(year int) bool { return year%400 == 0 || year%4 == 0 && year%100 != 0 }
Groovy
Solution:
(1900..2012).findAll {new GregorianCalendar().isLeapYear(it)}.each {println it}
{{out}}
1904 1908 1912 1916 1920 1924 1928 1932 1936 1940 1944 1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 2004 2008 2012 ``` =={{header|GW-BASIC}}== {{works with|PC-BASIC|any}} ```qbasic 10 ' Leap year 20 DEF FN ISLEAPYEAR(Y%) = ((Y% MOD 4 = 0) AND (Y% MOD 100 <> 0)) OR (Y% MOD 400 = 0) 95 ' *** Test *** 100 FOR I% = 1 TO 5 110 READ YEAR% 120 PRINT YEAR%; "is "; 130 IF FN ISLEAPYEAR(YEAR%) = 0 THEN PRINT "not "; ELSE PRINT ""; 140 PRINT "a leap year." 150 NEXT I% 160 END 200 DATA 1900, 1994, 1996, 1997, 2000 ``` {{out}} ```txt 1900 is not a leap year. 1994 is not a leap year. 1996 is a leap year. 1997 is not a leap year. 2000 is a leap year. ``` ## Harbour ```visualfoxpro FUNCTION IsLeapYear( nYear ) RETURN iif( nYear % 100 == 0, nYear % 400 == 0, nYear % 4 == 0 ) ``` ## Haskell '''Simple version''' ```haskell import Data.List import Control.Monad import Control.Arrow leaptext x b | b = show x ++ " is a leap year" | otherwise = show x ++ " is not a leap year" isleapsf j | 0==j`mod`100 = 0 == j`mod`400 | otherwise = 0 == j`mod`4 ``` '''Algorithmic''' ```haskell isleap = foldl1 ((&&).not).flip map [400, 100, 4]. ((0==).).mod ``` Example using isleap ```haskell *Main> mapM_ (putStrLn. (ap leaptext isleap)) [1900,1994,1996,1997,2000] 1900 is not a leap year 1994 is not a leap year 1996 is a leap year 1997 is not a leap year 2000 is a leap year ``` '''TDD version''' ```haskell import Test.HUnit isLeapYear::Int->Bool isLeapYear y | mod y 400 == 0 = True | mod y 100 == 0 = False | mod y 4 == 0 = True | otherwise = False tests = TestList[TestCase $ assertEqual "4 is a leap year" True $ isLeapYear 4 ,TestCase $ assertEqual "1 is not a leap year" False $ isLeapYear 1 ,TestCase $ assertEqual "64 is a leap year" True $ isLeapYear 64 ,TestCase $ assertEqual "2000 is a leap year" True $ isLeapYear 2000 ,TestCase $ assertEqual "1900 is not a leap year" False $ isLeapYear 1900] ``` ## Hy ```clojure (defn leap? [y] (and (= (% y 4) 0) (or (!= (% y 100) 0) (= (% y 400) 0)))) ``` =={{header|Icon}} and {{header|Unicon}}== Gives leap year status for 2000,1900,2012 and any arguments you give ```Icon procedure main(arglist) every y := !([2000,1900,2012]|||arglist) do write("The year ",y," is ", leapyear(y) | "not ","a leap year.") end procedure leapyear(year) #: determine if year is leap if (numeric(year) % 4 = 0 & year % 100 ~= 0) | (numeric(year) % 400 = 0) then return end ``` ## J ```j isLeap=: 0 -/@:= 4 100 400 |/ ] ``` Example use: ```j isLeap 1900 1996 1997 2000 0 1 0 1 ``` ## Java By default, [http://docs.oracle.com/javase/7/docs/api/index.html?java/util/GregorianCalendar.html java.util.GregorianCalendar] switches from Julian calendar to Gregorian calendar at 15 October 1582. The code below uses both the GregorianCalendar class and the algorithm from the wiki. Both values are printed in the output. ```java import java.util.GregorianCalendar; import java.text.MessageFormat; public class Leapyear{ public static void main(String[] argv){ int[] yrs = {1800,1900,1994,1998,1999,2000,2001,2004,2100}; GregorianCalendar cal = new GregorianCalendar(); for(int year : yrs){ System.err.println(MessageFormat.format("The year {0,number,#} is leaper: {1} / {2}.", year, cal.isLeapYear(year), isLeapYear(year))); } } public static boolean isLeapYear(int year){ return (year % 100 == 0) ? (year % 400 == 0) : (year % 4 == 0); } } ``` {{out}} ```txt The year 1800 is leaper: false / false. The year 1900 is leaper: false / false. The year 1994 is leaper: false / false. The year 1998 is leaper: false / false. The year 1999 is leaper: false / false. The year 2000 is leaper: true / true. The year 2001 is leaper: false / false. The year 2004 is leaper: true / true. The year 2100 is leaper: false / false. ``` {{works with|Java|8}} ```java import java.time.Year; public class IsLeap { public static void main(String[] args) { System.out.println(Year.isLeap(2004)); } } ``` ## JavaScript ```javascript var isLeapYear = function (year) { return (year % 100 === 0) ? (year % 400 === 0) : (year % 4 === 0); }; ``` Or, by setting the day to the 29th and checking if the day remains ```javascript // Month values start at 0, so 1 is for February var isLeapYear = function (year) { return new Date(year, 1, 29).getDate() === 29; }; ``` ## jq {{trans|Julia}} ```jq def leap: . as $y | ($y%4) == 0 and ($y < 1582 or ($y%400) == 0 or ($y%100) != 0); ``` '''Examples''': ```jq def assert(value; f): value as $value | ($value|f) | if . then empty else error("assertion violation: \($value) => \(.)") end; ((2400, 2012, 2000, 1600, 1500, 1400) | assert(.; leap)), ((2100, 2014, 1900, 1800, 1700, 1499) | assert(.; leap|not)) ``` {{out}} $ jq -n -f Leap_year.jq ## Julia {{works with|Julia|0.6}} ```julia isleap(yr::Integer) = yr % 4 == 0 && (yr < 1582 || yr % 400 == 0 || yr % 100 != 0) @assert all(isleap, [2400, 2012, 2000, 1600, 1500, 1400]) @assert !any(isleap, [2100, 2014, 1900, 1800, 1700, 1499]) ``` ## K ```K leapyear:{(+/~x!'4 100 400)!2} a@&leapyear'a:1900,1994,1996,1997,2000 1996 2000 ``` ## Kotlin ```kotlin fun isLeapYear(year: Int) = year % 400 == 0 || (year % 100 != 0 && year % 4 == 0) ``` ## Lasso ```Lasso define isLeapYear(y::integer) => { #y % 400 == 0 ? return true #y % 100 == 0 ? return false #y % 4 == 0 ? return true return false } with test in array(2012,2016,1933,1900,1999,2000) do => {^ isLeapYear(#test) '\r' ^} ``` {{out}} ```txt true true false false false true ``` ## Liberty BASIC ### Simple method ```lb if leap(1996)then print "leap" else print "ordinary" end if wait function leap(n) leap=date$("2/29/";n) end function ``` ### Calculated method ```lb year = 1908 select case case year mod 400 = 0 leapYear = 1 case year mod 4 = 0 and year mod 100 <> 0 leapYear = 1 case else leapYear = 0 end select if leapYear = 1 then print year;" is a leap year." else print year;" is not a leap year." end if ``` ## Lingo ```lingo on isLeapYear (year) return date(year, 2, 29).month=2 end ``` ## LiveCode ```LiveCode function isLeapYear year return (year MOD 4 is 0) AND ((year MOD 400 is 0) OR (year MOD 100 is not 0)) end isLeapYear command testLeapYear set itemDelimiter to comma put "1900,1994,1996,1997,2000" into years repeat for each item y in years put y && "is" && isLeapYear(y) && return after tyears end repeat put tyears end testLeapYear 1900 is false 1994 is false 1996 is true 1997 is false 2000 is true ``` ## LLVM ```llvm ; This is not strictly LLVM, as it uses the C library function "printf". ; LLVM does not provide a way to print values, so the alternative would be ; to just load the string into memory, and that would be boring. $"EMPTY_STR" = comdat any $"NOT_STR" = comdat any $"IS_A_LEAP_YEAR" = comdat any @main.test_case = private unnamed_addr constant [5 x i32] [i32 1900, i32 1994, i32 1996, i32 1997, i32 2000], align 16 @"EMPTY_STR" = linkonce_odr unnamed_addr constant [1 x i8] zeroinitializer, comdat, align 1 @"NOT_STR" = linkonce_odr unnamed_addr constant [5 x i8] c"not \00", comdat, align 1 @"IS_A_LEAP_YEAR" = linkonce_odr unnamed_addr constant [22 x i8] c"%d is %sa leap year.\0A\00", comdat, align 1 ;--- The declaration for the external C printf function. declare i32 @printf(i8*, ...) ; Function Attrs: noinline nounwind optnone uwtable define i32 @is_leap_year(i32) #0 { %2 = alloca i32, align 4 ;-- allocate a local copy of year store i32 %0, i32* %2, align 4 ;-- store a copy of year %3 = load i32, i32* %2, align 4 ;-- load the year %4 = srem i32 %3, 4 ;-- year % 4 %5 = icmp ne i32 %4, 0 ;-- (year % 4) != 0 br i1 %5, label %c1false, label %c1true c1true: %6 = load i32, i32* %2, align 4 ;-- load the year %7 = srem i32 %6, 100 ;-- year % 100 %8 = icmp ne i32 %7, 0 ;-- (year % 100) != 0 br i1 %8, label %c2true, label %c1false c1false: %9 = load i32, i32* %2, align 4 ;-- load the year %10 = srem i32 %9, 400 ;-- year % 400 %11 = icmp ne i32 %10, 0 ;-- (year % 400) != 0 %12 = xor i1 %11, true br label %c2true c2true: %13 = phi i1 [ true, %c1true ], [ %12, %c1false ] %14 = zext i1 %13 to i64 %15 = select i1 %13, i32 1, i32 0 ret i32 %15 } ; Function Attrs: noinline nounwind optnone uwtable define i32 @main() #0 { %1 = alloca [5 x i32], align 16 ;-- allocate test_case %2 = alloca i32, align 4 ;-- allocate key %3 = alloca i32, align 4 ;-- allocate end %4 = alloca i32, align 4 ;-- allocate year %5 = bitcast [5 x i32]* %1 to i8* call void @llvm.memcpy.p0i8.p0i8.i64(i8* %5, i8* bitcast ([5 x i32]* @main.test_case to i8*), i64 20, i32 16, i1 false) store i32 0, i32* %2, align 4 ;-- store 0 in key store i32 5, i32* %3, align 4 ;-- store 5 in end br label %loop loop: %6 = load i32, i32* %2, align 4 ;-- load key %7 = load i32, i32* %3, align 4 ;-- load end %8 = icmp slt i32 %6, %7 ;-- key < end br i1 %8, label %loop_body, label %exit loop_body: %9 = load i32, i32* %2, align 4 ;-- load key %10 = sext i32 %9 to i64 ;-- sign extend key %11 = getelementptr inbounds [5 x i32], [5 x i32]* %1, i64 0, i64 %10 %12 = load i32, i32* %11, align 4 ;-- load test_case[key] store i32 %12, i32* %4, align 4 ;-- store test_case[key] as year %13 = load i32, i32* %4, align 4 ;-- load year %14 = call i32 @is_leap_year(i32 %13) ;-- is_leap_year(year) %15 = icmp eq i32 %14, 1 ;-- is_leap_year(year) == 1 %16 = zext i1 %15 to i64 ;-- zero extend %17 = select i1 %15, i8* getelementptr inbounds ([1 x i8], [1 x i8]* @"EMPTY_STR", i32 0, i32 0), i8* getelementptr inbounds ([5 x i8], [5 x i8]* @"NOT_STR", i32 0, i32 0) %18 = load i32, i32* %4, align 4 ;-- load year %19 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([22 x i8], [22 x i8]* @"IS_A_LEAP_YEAR", i32 0, i32 0), i32 %18, i8* %17) %20 = load i32, i32* %2, align 4 ;-- load key %21 = add nsw i32 %20, 1 ;-- increment key store i32 %21, i32* %2, align 4 ;-- store key br label %loop exit: ret i32 0 } ; Function Attrs: argmemonly nounwind declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1) #1 attributes #0 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" } attributes #1 = { argmemonly nounwind } ``` {{out}} ```txt 1900 is not a leap year. 1994 is not a leap year. 1996 is a leap year. 1997 is not a leap year. 2000 is a leap year. ``` ## Logo ```logo to multiple? :n :d output equal? 0 modulo :n :d end to leapyear? :y output ifelse multiple? :y 100 [multiple? :y 400] [multiple? :y 4] end ``` ## Logtalk ```logtalk leap_year(Year) :- ( mod(Year, 4) =:= 0, mod(Year, 100) =\= 0 -> true ; mod(Year, 400) =:= 0 ). ``` ## LOLCODE ```lolcode BTW Determine if a Gregorian calendar year is leap HAI 1.3 HOW IZ I Leap YR Year BOTH SAEM 0 AN MOD OF Year AN 4 O RLY? YA RLY BOTH SAEM 0 AN MOD OF Year AN 100 O RLY? YA RLY BOTH SAEM 0 AN MOD OF Year AN 400 O RLY? YA RLY FOUND YR WIN NO WAI FOUND YR FAIL OIC NO WAI FOUND YR WIN OIC NO WAI FOUND YR FAIL OIC IF U SAY SO I HAS A Yearz ITZ A BUKKIT Yearz HAS A SRS 0 ITZ 1900 Yearz HAS A SRS 1 ITZ 1904 Yearz HAS A SRS 2 ITZ 1994 Yearz HAS A SRS 3 ITZ 1996 Yearz HAS A SRS 4 ITZ 1997 Yearz HAS A SRS 5 ITZ 2000 IM IN YR Loop UPPIN YR Index WILE DIFFRINT Index AN 6 I HAS A Yr ITZ Yearz'Z SRS Index I HAS A Not I IZ Leap YR Yr MKAY O RLY? YA RLY Not R "" NO WAI Not R " NOT" OIC VISIBLE Yr " is" Not " a leap year" IM OUTTA YR Loop KTHXBYE ``` {{Out}} ```txt 1900 is NOT a leap year 1904 is a leap year 1994 is NOT a leap year 1996 is a leap year 1997 is NOT a leap year 2000 is a leap year ``` ## Lua ```Lua function isLeapYear(year) return year%4==0 and (year%100~=0 or year%400==0) end ``` ## Maple ```maple isLeapYear := proc(year) if not year mod 4 = 0 or (year mod 100 = 0 and not year mod 400 = 0) then return false; else return true; end if; end proc: ``` ## Mathematica Dates are handled by built-in functions in the Wolfram Language ```Mathematica LeapYearQ[2002] ``` =={{header|MATLAB}} / {{header|Octave}}== MATLAB, conveniently, provides a function that returns the last day of an arbitrary month of the calendar given the year. Using the fact that February is 29 days long during a leap year, we can write a one-liner that solves this task. ```MATLAB function TrueFalse = isLeapYear(year) TrueFalse = (eomday(year,2) == 29); end ``` ### Using Logical and modular functions ```matlab x = ~mod(YEAR, 4) & (mod(YEAR, 100) | ~mod(YEAR, 400)) ``` ## Maxima ```maxima leapyearp(year) := is(mod(year, 4) = 0 and (mod(year, 100) # 0 or mod(year, 400) = 0))$ ``` =={{header|МК-61/52}}==П0 1 0 0 / {x} x=0 14 ИП0 4 0 0 ПП 18 ИП0 4 ПП 18 / {x} x=0 24 1 С/П 0 С/П ``` ## Mercury ```mercury :- pred is_leap_year(int::in) is semidet. is_leap_year(Year) :- ( if Year mod 100 = 0 then Year mod 400 = 0 else Year mod 4 = 0 ). ``` Usage: ```mercury :- module leap_year. :- interface. :- import_module io. :- pred main(io::di, io::uo) is det. :- implementation. :- import_module int, list, string. main(!IO) :- Years = [1600, 1700, 1899, 1900, 2000, 2006, 2012], io.write_list(Years, "", write_year_kind, !IO). :- pred write_year_kind(int::in, io::di, io::uo) is det. write_year_kind(Year, !IO) :- io.format("%d %s a leap year.\n", [i(Year), s(if is_leap_year(Year) then "is" else "is not" )], !IO). ``` ## MiniScript ```MiniScript isLeapYear = function(year) return year%4==0 and (year % 100 or not year % 400) end function ``` ## MIPS Assembly Pass year in a0, returns boolean in v0. ```mips IsLeap: andi $a1, $a0, 3 #a0 is year to test bnez $a1 NotLeap li $a1, 100 div $a0, $a1 mfhi $a1 bnez $a1, Leap mflo $a1 andi $a1, $a1, 3 bnez $a1, NotLeap Leap: li $v0, 1 jr $ra NotLeap:li $v0, 0 jr $ra ``` =={{header|Modula-2}}== ```modula2 MODULE LeapYear; FROM FormatString IMPORT FormatString; FROM Terminal IMPORT WriteString,ReadChar; PROCEDURE IsLeapYear(year : INTEGER) : BOOLEAN; BEGIN IF year MOD 100 = 0 THEN RETURN year MOD 400 = 0; END; RETURN year MOD 4 = 0 END IsLeapYear; PROCEDURE Print(year : INTEGER); VAR buf : ARRAY[0..63] OF CHAR; leap : BOOLEAN; BEGIN leap := IsLeapYear(year); FormatString("Is %i a leap year? %b\n", buf, year, leap); WriteString(buf) END Print; BEGIN Print(1900); Print(1994); Print(1996); Print(1997); Print(2000); ReadChar END LeapYear. ``` ## MUMPS ```MUMPS ILY(X) ;IS IT A LEAP YEAR? QUIT ((X#4=0)&(X#100'=0))!((X#100=0)&(X#400=0)) ``` Usage: ```txt USER>W $SELECT($$ILY^ROSETTA(1900):"Yes",1:"No") No USER>W $SELECT($$ILY^ROSETTA(2000):"Yes",1:"No") Yes USER>W $SELECT($$ILY^ROSETTA(1999):"Yes",1:"No") No ``` ## Neko Translating from C ```ActionScript /** **/ var leapyear = function(y) return ($not(y % 4) && $istrue(y % 100) || $not(y % 400)) var tests = $array(2000, 1997, 1996, 1994, 1990, 1980, 1900) var cnt = $asize(tests) while (cnt -= 1) >= 0 $print(tests[cnt], if leapyear(tests[cnt]) " is" else " is not", " a leapyear", "\n") ``` {{out}} ```txt prompt$ nekoc leapyear.neko prompt$ neko leapyear.n 1900 is not a leapyear 1980 is a leapyear 1990 is not a leapyear 1994 is not a leapyear 1996 is a leapyear 1997 is not a leapyear 2000 is a leapyear ``` ## Nemerle Demonstrating implementation as well as use of standard library function. ```Nemerle using System; using System.Console; using Nemerle.Assertions; using Nemerle.Imperative; module LeapYear { IsLeapYear(year : int) : bool requires year >= 1582 otherwise throw ArgumentOutOfRangeException("year must be in Gregorian calendar.") // without the contract enforcement would work for proleptic Gregorian Calendar // in that case we might still want to require year > 0 { when (year % 400 == 0) return true; when (year % 100 == 0) return false; when (year % 4 == 0) return true; false } Main() : void { WriteLine("2000 is a leap year: {0}", IsLeapYear(2000)); WriteLine("2100 is a leap year: {0}", IsLeapYear(2100)); try { WriteLine("1500 is a leap year: {0}", IsLeapYear(1500)); } catch { |e is ArgumentOutOfRangeException => WriteLine(e.Message) } WriteLine("1500 is a leap year: {0}", DateTime.IsLeapYear(1500)); // is false, indicating use of proleptic // Gregorian calendar rather than reverting to // Julian calendar WriteLine("{0} is a leap year: {1}", DateTime.Now.Year, DateTime.IsLeapYear(DateTime.Now.Year)); } } ``` {{out}} ```txt 2000 is a leap year: True 2100 is a leap year: False Specified argument was out of the range of valid values. Parameter name: year must be in Gregorian calendar. 1500 is a leap year: False 2013 is a leap year: False ``` ## NetRexx Demonstrates both a '''Gregorian/proleptic Gregorian''' calendar leap-year algorithm and use of the Java library's Leap year, in Neko
GregorianCalendar
object to determine which years are leap-years. Note that the Java library indicates that the year '''1500''' is a leap-year as the Gregorian calendar wasn't established until 1582. The Java library implements the Julian calendar for dates prior to the Gregorian cut-over and leap-year rules in the Julian calendar are different to those for the Gregorian calendar. ```NetRexx /* NetRexx */ options replace format comments java crossref savelog symbols nobinary years = '1500 1580 1581 1582 1583 1584 1600 1700 1800 1900 1994 1996 1997 2000 2004 2008 2009 2010 2011 2012 2100 2200 2300 2400 2500 2600' years['l-a'] = '' years['n-a'] = '' years['l-j'] = '' years['n-j'] = '' loop y_ = 1 to years.words year = years.word(y_) if isLeapyear(year) then years['l-a'] = years['l-a'] year else years['n-a'] = years['n-a'] year if GregorianCalendar().isLeapYear(year) then years['l-j'] = years['l-j'] year else years['n-j'] = years['n-j'] year end y_ years['l-a'] = years['l-a'].strip years['n-a'] = years['n-a'].strip years['l-j'] = years['l-j'].strip years['n-j'] = years['n-j'].strip say ' Sample years:' years['all'].changestr(' ', ',') say ' Leap years (algorithmically):' years['l-a'].changestr(' ', ',') say ' Leap years (Java library) :' years['l-j'].changestr(' ', ',') say ' Non-leap years (algorithmically):' years['n-a'].changestr(' ', ',') say ' Non-leap years (Java library) :' years['n-j'].changestr(' ', ',') return -- algorithmically method isLeapyear(year = int) public constant binary returns boolean select when year // 400 = 0 then ly = isTrue when year // 100 \= 0 & year // 4 = 0 then ly = isTrue otherwise ly = isFalse end return ly method isTrue public constant binary returns boolean return 1 == 1 method isFalse public constant binary returns boolean return \isTrue ``` {{out}} ```txt Sample years: 1500,1580,1581,1582,1583,1584,1600,1700,1800,1900,1994,1996,1997,2000,2004,2008,2009,2010,2011,2012,2100,2200,2300,2400,2500,2600 Leap years (algorithmically): 1580,1584,1600,1996,2000,2004,2008,2012,2400 Leap years (Java library) : 1500,1580,1584,1600,1996,2000,2004,2008,2012,2400 Non-leap years (algorithmically): 1500,1581,1582,1583,1700,1800,1900,1994,1997,2009,2010,2011,2100,2200,2300,2500,2600 Non-leap years (Java library) : 1581,1582,1583,1700,1800,1900,1994,1997,2009,2010,2011,2100,2200,2300,2500,2600 ``` =={{Header|Nim}}== ```nim import times let year = 1980 echo isLeapYear(year) # or proc isLeapYear2(year): bool = if year mod 100 == 0: year mod 400 == 0 else: year mod 4 == 0 echo isLeapYear2(year) ``` {{out}} ```txt true true ``` =={{Header|Oberon-2}}== ```oberon2 PROCEDURE IsLeapYear(year: INTEGER): BOOLEAN; BEGIN IF year MOD 4 # 0 THEN RETURN FALSE ELSE IF year MOD 100 = 0 THEN IF year MOD 400 = 0 THEN RETURN TRUE ELSE RETURN FALSE END ELSE RETURN TRUE END END END IsLeapYear; ``` ## Objeck ```objeck bundle Default { class LeapYear { function : Main(args : String[]) ~ Nil { test_case := [1900, 1994, 1996, 1997, 2000]; each(i : test_case) { test_case[i]->Print(); if(IsLeapYear(test_case[i])) { " is a leap year."->PrintLine(); } else { " is not a leap year."->PrintLine(); }; }; } function : native : IsLeapYear(year : Int) ~ Bool { if(year % 4 = 0 & year % 100 <> 0) { return true; } else if(year % 400 = 0) { return true; }; return false; } } } ``` ## OCaml ```ocaml let is_leap_year ~year = if (year mod 100) = 0 then (year mod 400) = 0 else (year mod 4) = 0 ``` Using Unix Time functions: ```ocaml let is_leap_year ~year = let tm = Unix.mktime { (Unix.gmtime (Unix.time())) with Unix.tm_year = (year - 1900); tm_mon = 1 (* feb *); tm_mday = 29 } in (tm.Unix.tm_mday = 29) ``` ## Oforth ```Oforth Date.IsLeapYear(2000) ``` ## ooRexx ```ooRexx ::routine isLeapYear use arg year d = .datetime~new(year, 1, 1) return d~isLeapYear ``` ## OpenEdge/Progress The DATE function converts month, day, year integers to a date data type and will set the error status if invalid values are passed. ```progress FUNCTION isLeapYear RETURNS LOGICAL ( i_iyear AS INTEGER ): DATE( 2, 29, i_iyear ) NO-ERROR. RETURN NOT ERROR-STATUS:ERROR. END FUNCTION. /* isLeapYear */ MESSAGE 1900 isLeapYear( 1900 ) SKIP 1994 isLeapYear( 1994 ) SKIP 1996 isLeapYear( 1996 ) SKIP 1997 isLeapYear( 1997 ) SKIP 2000 isLeapYear( 2000 ) VIEW-AS ALERT-BOX. ``` ## Oz ```oz declare fun {IsLeapYear Year} case Year mod 100 of 0 then Year mod 400 == 0 else Year mod 4 == 0 end end in for Y in [1900 1996 1997 2000] do if {IsLeapYear Y} then {System.showInfo Y#" is a leap year."} else {System.showInfo Y#" is NOT a leap year."} end end ``` {{out}} ```txt 1900 is NOT a leap year. 1996 is a leap year. 1997 is NOT a leap year. 2000 is a leap year. ``` ## PARI/GP ```parigp isLeap(n)={ if(n%400==0, return(1)); if(n%100==0, return(0)); n%4==0 }; ``` Alternate version: ```parigp isLeap(n)=!(n%if(n%100,4,400)) ``` {{works with|PARI/GP|2.6.0 and above}} ```parigp isLeap(n)={ if(n%4,0, n%100,1, n%400,0,1 ) }; ``` ## Pascal {{works with|Free Pascal}} ```pascal program LeapYear; uses sysutils;//includes isLeapYear procedure TestYear(y: word); begin if IsLeapYear(y) then writeln(y,' is a leap year') else writeln(y,' is NO leap year'); end; Begin TestYear(1900); TestYear(2000); TestYear(2100); TestYear(1904); end. ``` Output: ```txt 1900 is NO leap year 2000 is a leap year 2100 is NO leap year 1904 is a leap year ``` ## Perl ```Perl sub isleap { my $year = shift; if ($year % 100 == 0) { return ($year % 400 == 0); } return ($year % 4 == 0); } ``` Or more concisely: ```Perl sub isleap { !($_[0] % 100) ? !($_[0] % 400) : !($_[0] % 4) } ``` Alternatively, using functions/methods from CPAN modules: ```Perl use Date::Manip; print Date_LeapYear(2000); use Date::Manip::Base; my $dmb = new Date::Manip::Base; print $dmb->leapyear(2000); use DateTime; my $date = DateTime->new(year => 2000); print $date->is_leap_year(); ``` ## Perl 6 {{works with|Rakudo|2010.07}} ```perl6 say "$year is a {Date.is-leap-year($year) ?? 'leap' !! 'common'} year." ``` In Rakudo 2010.07,Date.is-leap-year
is implemented as ```perl6 multi method is-leap-year($y = $!year) { $y %% 4 and not $y %% 100 or $y %% 400 } ``` ## Phix Available as an auto-include, implemented as: ```Phix global function is_leap_year(integer y) return remainder(y,4)=0 and (remainder(y,100)!=0 or remainder(y,400)=0) end function ``` ## PHP ```php date('L'): ```php NIL : (isLeapYear 2008) -> T : (isLeapYear 1600) -> T : (isLeapYear 1700) -> NIL ``` ## PL/I ```pli dcl mod builtin; dcl year fixed bin (31); do year = 1900, 1996 to 2001; if mod(year, 4) = 0 & (mod(year, 100) ^= 0 | mod(year, 400) = 0) then put skip edit(year, 'is a leap year') (p'9999b', a); else put skip edit(year, 'is not a leap year') (p'9999b', a); end; ``` {{out}} ```txt 1900 is not a leap year 1996 is a leap year 1997 is not a leap year 1998 is not a leap year 1999 is not a leap year 2000 is a leap year 2001 is not a leap year ``` ## PostScript ```postscript /isleapyear { dup dup 4 mod 0 eq % needs to be divisible by 4 exch 100 mod 0 ne % but not by 100 and exch 400 mod 0 eq % or by 400 or } def ``` ## PowerShell ```powershell $Year = 2016 [System.DateTime]::IsLeapYear( $Year ) ``` ## Prolog {{Works with|SWI-Prolog}} ```Prolog leap_year(L) :- partition(is_leap_year, L, LIn, LOut), format('leap years : ~w~n', [LIn]), format('not leap years : ~w~n', [LOut]). is_leap_year(Year) :- R4 is Year mod 4, R100 is Year mod 100, R400 is Year mod 400, ( (R4 = 0, R100 \= 0); R400 = 0). ``` {{out}} ```Prolog ?- leap_year([1900,1994,1996,1997,2000 ]). leap years : [1996,2000] not leap years : [1900,1994,1997] L = [1900,1994,1996,1997,2000]. ``` There is an handy builtin that simplifies a lot, ending up in a simple query: ```Prolog ?- findall(Y, (between(1990,2030,Y),day_of_the_year(date(Y,12,31),366)), L). L = [1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028]. ``` ## PureBasic ```PureBasic Procedure isLeapYear(Year) If (Year%4=0 And Year%100) Or Year%400=0 ProcedureReturn #True Else ProcedureReturn #False EndIf EndProcedure ``` ## Python ```python import calendar calendar.isleap(year) ``` or ```python def is_leap_year(year): if year % 100 == 0: return year % 400 == 0 return year % 4 == 0 ``` Asking for forgiveness instead of permission: ```python import datetime def is_leap_year(year): try: datetime.date(year, 2, 29) except ValueError: return False return True ``` ## Q ```q ly:{((0<>x mod 100) | 0=x mod 400) & 0=x mod 4} / Return 1b if x is a leap year; 0b otherwise ``` ## R ```R isLeapYear <- function(year) { ifelse(year%%100==0, year%%400==0, year%%4==0) } for (y in c(1900, 1994, 1996, 1997, 2000)) { cat(y, ifelse(isLeapYear(y), "is", "isn't"), "a leap year.\n") } ``` {{out}} ```txt 1900 isn't a leap year. 1994 isn't a leap year. 1996 is a leap year. 1997 isn't a leap year. 2000 is a leap year. ``` ## Racket ```racket (define (leap-year? y) (and (zero? (modulo y 4)) (or (positive? (modulo y 100)) (zero? (modulo y 400))))) ``` ## Raven ```Raven define is_leap_year use $year $year 100 % 0 = if $year 400 % 0 = $year 4 % 0 = ``` ## REBOL ```rebol leap-year?: func [ {Returns true if the specified year is a leap year; false otherwise.} year [date! integer!] /local div? ][ either date? year [year: year/year] [ if negative? year [throw make error! join [script invalid-arg] year] ] ; The key numbers are 4, 100, and 400, combined as follows: ; 1) If the year is divisible by 4, it’s a leap year. ; 2) But, if the year is also divisible by 100, it’s not a leap year. ; 3) Double but, if the year is also divisible by 400, it is a leap year. div?: func [n] [zero? year // n] to logic! any [all [div? 4 not div? 100] div? 400] ] ``` ## Retro ```Retro : isLeapYear? ( y-f ) dup 400 mod 0 = [ drop -1 0 ] [ 1 ] if 0; drop dup 100 mod 0 = [ drop 0 0 ] [ 1 ] if 0; drop 4 mod 0 = ; ``` This is provided by the standard '''calendar''' library. ## REXX ### local variables ```rexx leapyear: procedure; parse arg yr return yr//400==0 | (yr//100\==0 & yr//4==0) ``` ===with short-circuit=== The REXX language doesn't support short-circuits, so here is a version that does a short-circuit. ```rexx leapyear: procedure; parse arg yr if yr//4\==0 then return 0 /*Not ÷ by 4? Not a leap year.*/ return yr//400==0 | yr//100\==0 ``` ### no local variables This version doesn't need a PROCEDURE to hide local variable(s) [because there aren't any local variables], but it does invoke the '''ARG''' BIF multiple times. ```rexx leapyear: if arg(1)//4\==0 then return 0 return arg(1)//400==0 | arg(1)//100\==0 ``` ### handles 2 digit year This REXX version has the proviso that if the year is exactly two digits, the current century is assumed (i.e., no ''year'' windowing). If a year below 100 is to be used, the year should have leading zeroes added (to make it four digits). ```rexx leapyear: procedure; parse arg y /*year could be: Y, YY, YYY, YYYY*/ if y//4\==0 then return 0 /*Not ÷ by 4? Not a leap year.*/ if length(y)==2 then y=left(date('S'),2)y /*adjust for a 2─digit YY year.*/ return y//100\==0 | y//400==0 /*apply 100 and 400 year rule. */ ``` ## Ring ```ring give year leap = isLeapYear(year) if leap true see year + " is leap year." else see year + " is not leap year." ok Func isLeapYear year if (year % 400) = 0 return true but (year % 100) = 0 return false but (year % 4) = 0 return true else return false ok ``` ## RPG {{works with|RPGIII|}} ```RPG C*0N01N02N03Factor1+++OpcdeFactor2+++ResultLenDHHiLoEqComments+++++++ C *ENTRY PLIST C PARM YEAR 40 input (year) C PARM ISLEAP 1 output (Y/N) C* C MOVE 'N' ISLEAP C YEAR CABLE1752 DONE not Gregorian C* C YEAR DIV 4 RESULT 40 C MVR REMAIN 40 C REMAIN CABNE0 DONE C* C* If we got here, year is divisible by 4. C YEAR DIV 100 RESULT C MVR REMAIN C REMAIN CABNE0 LEAPYR C* C* If we got here, year is divisible by 100. C YEAR DIV 400 RESULT C MVR REMAIN C REMAIN CABNE0 DONE C* C LEAPYR TAG C MOVE 'Y' ISLEAP C* C DONE TAG C SETON LR ``` ## Ruby ```ruby require 'date' Date.leap?(year) ``` The leap? method is aliased as gregorian_leap? And yes, there is a julian_leap? method. ## Run BASIC ```runbasic if date$("02/29/" + mid$(date$("mm/dd/yyyy"),7,4)) then print "leap year" else print "not" ``` ## Rust ```rust fn is_leap(year: i32) -> bool { let factor = |x| year % x == 0; factor(4) && (!factor(100) || factor(400)) } ``` =={{header|S-BASIC}}== Since S-BASIC has no MOD operator or function, we have to supply one. ```basic rem - compute p mod q function mod(p, q = integer) = integer end = p - q * (p/q) rem - return true (-1) if y is a leap year, otherwise 0 function isleapyear(y = integer) = integer end = mod(y,4)=0 and mod(y,100)<>0 or mod(y,400)=0 rem - exercise the function var y = integer print "Test of century years" for y = 1600 to 2000 step 100 if isleapyear(y) then print y;" is a leap year" else print y;" is NOT a leap year" next y print "Test of current half-decade" for y = 2015 to 2020 if isleapyear(y) then print y; " is a leap year" else print y; " is NOT a leap year" next y end ``` {{out}} ```txt Test of century years 1600 is a leap year 1700 is NOT a leap year 1800 is NOT a leap year 1900 is NOT a leap year 2000 is a leap year Test of current half-decade 2015 is NOT a leap year 2016 is a leap year 2017 is NOT a leap year 2018 is NOT a leap year 2019 is NOT a leap year 2020 is a leap year ``` ## Scala ===JDK 7 (not recommended)=== By default, [http://docs.oracle.com/javase/7/docs/api/index.html?java/util/GregorianCalendar.html java.util.GregorianCalendar] switches from Julian calendar to Gregorian calendar at 15 October 1582. ```scala //use Java's calendar class new java.util.GregorianCalendar().isLeapYear(year) ``` ### JDK 8 Using JSR-310 java.time. ```scala java.time.LocalDate.ofYearDay(year, 1).isLeapYear() ``` ### Implementation For proleptic Gregorian calendar: ```scala def isLeapYear(year:Int)=if (year%100==0) year%400==0 else year%4==0; //or use Java's calendar class def isLeapYear(year:Int):Boolean = { val c = new java.util.GregorianCalendar c.setGregorianChange(new java.util.Date(Long.MinValue)) c.isLeapYear(year) } ``` ## Scheme ```scheme (define (leap-year? n) (apply (lambda (a b c) (or a (and (not b) c))) (map (lambda (m) (zero? (remainder n m))) '(400 100 4)))) ``` ## Seed7 This function is part of the "time.s7i" library. It returns TRUE if the year is a leap year in the Gregorian calendar. ```seed7 const func boolean: isLeapYear (in integer: year) is return (year rem 4 = 0 and year rem 100 <> 0) or year rem 400 = 0; ``` Original source: [http://seed7.sourceforge.net/algorith/date.htm#isLeapYear] ## Sidef ```ruby func isleap(year) { if (year %% 100) { return (year %% 400); } return (year %% 4); } ``` or a little bit simpler: ```ruby func isleap(year) { year %% 100 ? (year %% 400) : (year %% 4) }; ``` ## Smalltalk Smalltalk has a built-in method named isLeapYear: ```smalltalk Date today isLeapYear. ``` ## SNOBOL4 Predicate leap( ) succeeds/fails, returns nil. ```SNOBOL4 define('leap(yr)') :(end_leap) leap eq(remdr(yr,400),0) :s(return) eq(remdr(yr,100),0) :s(freturn) eq(remdr(yr,4),0) :s(return)f(freturn) end_leap * # Test and display (with ?: kluge) test = "output = ('10' ? (*leap(yr) 1 | 0)) ': ' yr" yr = '1066'; eval(test) yr = '1492'; eval(test) yr = '1900'; eval(test) yr = '2000'; eval(test) end ``` {{out}} ```txt 0: 1066 1: 1492 0: 1900 1: 2000 ``` ## Stata Given a dataset with a "year" variable, generate a variable "leap" which is 1 for a leap year, 0 otherwise. ```stata gen leap = mod(year,400)==0 | mod(year,4)==0 & mod(year,100)!=0 ``` See also the article '''[https://www.stata.com/support/faqs/data-management/leap-year-indicators/ How do I identify leap years in Stata?]''' by Nicholas J. Cox in Stata FAQ. ## Swift ```Swift func isLeapYear(year:Int) -> Bool { return (year % 100 == 0) ? (year % 400 == 0) : (year % 4 == 0) } print(isLeapYear(2000)) print(isLeapYear(2011)) ``` {{out}} ```txt true false ``` ## Tcl The "classic" modulo comparison: ```tcl proc isleap1 {year} { return [expr {($year % 4 == 0) && (($year % 100 != 0) || ($year % 400 == 0))}] } isleap1 1988 ;# => 1 isleap1 1989 ;# => 0 isleap1 1900 ;# => 0 isleap1 2000 ;# => 1 ``` Does Feb 29 exist in the given year? If not a leap year, the clock command will return "03-01". (This code will switch to the Julian calendar for years before 1582.) ```tcl proc isleap2 year { return [expr {[clock format [clock scan "$year-02-29" -format "%Y-%m-%d"] -format "%m-%d"] eq "02-29"}] } isleap2 1988 ;# => 1 isleap2 1989 ;# => 0 isleap2 1900 ;# => 0 isleap2 2000 ;# => 1 ``` ## TUSCRIPT ```tuscript $$ MODE TUSCRIPT LOOP year="1900'1994'1996'1997'2000",txt="" SET dayoftheweek=DATE(number,29,2,year,number) IF (dayoftheweek==0) SET txt="not " PRINT year," is ",txt,"a leap year" ENDLOOP ``` {{out}} ```txt 1900 is not a leap year 1994 is not a leap year 1996 is a leap year 1997 is not a leap year 2000 is a leap year ``` ## uBasic/4tH {{trans|BBC BASIC}}DO INPUT "Enter a year: "; y IF FUNC(_FNleap(y)) THEN PRINT y; " is a leap year" ELSE PRINT y; " is not a leap year" ENDIF LOOP END _FNleap Param (1) RETURN ((a@ % 4 = 0) * ((a@ % 400 = 0) + (a@ % 100 # 0))) ``` ## UNIX Shell Original Bourne: ```sh leap() { if expr $1 % 4 >/dev/null; then return 1; fi if expr $1 % 100 >/dev/null; then return 0; fi if expr $1 % 400 >/dev/null; then return 1; fi return 0; } ``` Using GNU date(1): ```sh leap() { date -d "$1-02-29" >/dev/null 2>&1; } ``` Defining a bash function is_leap which accepts a YEAR argument, and uses no IO redirection, nor any extra processes. ```sh is_leap() { local year=$(( 10#${1:?'Missing year'} )) (( year % 4 == 0 && ( year % 100 != 0 || year % 400 == 0 ) )) && return 0 return 1 } ``` Using the cal command: ''(note that this invokes two processes with IO piped between them and is relatively heavyweight compared to the above shell functions: leap and is_leap)'' ```sh leap() { cal 02 $1 | grep -q 29 } ``` ## Ursa This program takes a year as a command line argument. ```ursa decl int year set year (int args<1>) if (= (mod year 4) 0) if (and (= (mod year 100) 0) (not (= (mod year 400) 0))) out year " is not a leap year" endl console else out year " is a leap year" endl console end if else out year " is not a leap year" endl console end if ``` Output in Bash: ```txt $ ursa leapyear.u 1900 1900 is not a leap year $ ursa leapyear.u 2000 2000 is a leap year ``` ## Vala ```Vala void main() { DateYear[] years = {1900, 1994, 1996, 1997, 2000}; foreach (DateYear year in years) { string status = year.is_leap_year() ? "" : "not "; print("%d is %sa leap year.\n", (int) year, status); } } ``` ## VBA ```vb Public Function Leap_year(year As Integer) As Boolean Leap_year = (Month(DateSerial(year, 2, 29)) = 2) End Function ``` ## VBScript ```vb Function IsLeapYear(yr) IsLeapYear = False If yr Mod 4 = 0 And (yr Mod 400 = 0 Or yr Mod 100 <> 0) Then IsLeapYear = True End If End Function 'Testing the function. arr_yr = Array(1900,1972,1997,2000,2001,2004) For Each yr In arr_yr If IsLeapYear(yr) Then WScript.StdOut.WriteLine yr & " is leap year." Else WScript.StdOut.WriteLine yr & " is NOT leap year." End If Next ``` {{Out}} ```txt 1900 is NOT leap year. 1972 is leap year. 1997 is NOT leap year. 2000 is leap year. 2001 is NOT leap year. 2004 is leap year. ``` ## Vedit macro language ```vedit while (#1 = Get_Num("Year: ")) { #2 = (#1 % 4 == 0) && ((#1 % 100 != 0) || (#1 % 400 == 0)) if (#2) { Message(" is leap year\n") } else { Message(" is not leap year\n") } } ``` The following version requires Vedit 6.10 or later: ```vedit while (#1 = Get_Num("Year: ")) { if (Is_Leap_Year(#1)) { Message(" is leap year\n") } else { Message(" is not leap year\n") } } ``` ## Visual Basic {{works with|Visual Basic|VB6 Standard}} ```vb Public Function IsLeapYear1(ByVal theYear As Integer) As Boolean 'this function utilizes documented behaviour of the built-in DateSerial function IsLeapYear1 = (VBA.Day(VBA.DateSerial(theYear, 2, 29)) = 29) End Function Public Function IsLeapYear2(ByVal theYear As Integer) As Boolean 'this function uses the well-known formula IsLeapYear2 = IIf(theYear Mod 100 = 0, theYear Mod 400 = 0, theYear Mod 4 = 0) End Function ``` Testing: ```vb Sub Main() 'testing the above functions Dim i As Integer For i = 1750 To 2150 Debug.Assert IsLeapYear1(i) Eqv IsLeapYear2(i) Next i End Sub ``` ## Visual Basic .NET {{trans|C#}} ```vbnet Module Module1 Sub Main() For Each y In {1900, 1994, 1996, Date.Now.Year} Console.WriteLine("{0} is {1}a leap year.", y, If(Date.IsLeapYear(y), String.Empty, "not ")) Next End Sub End Module ``` {{out}} ```txt 1900 is not a leap year. 1994 is not a leap year. 1996 is a leap year. 2019 is not a leap year. ``` ## WDTE ```WDTE>let str = import 'strings'; let multiple of n => == (% n of) 0; let leap year => str.format '{} is{} a leap year.' year (switch year { multiple 400 => ''; multiple 100 => ' not'; multiple 4 => ''; default => ' not'; }) -- io.writeln io.stdout; ``` ## Wortel ```wortel @let { isLeapYear !?{\~%%1H \~%%4H \~%%4} !-isLeapYear @range[1900 2000] } ``` Returns: ```txt [1904 1908 1912 1916 1920 1924 1928 1932 1936 1940 1944 1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000] ``` ## X86 Assembly Using FASM syntax. Leaf function fits nicely into your program. ```asm align 16 ; Input year as signed dword in EAX IsLeapYear: test eax,11b jz .4 retn ; 75% : ZF=0, not a leap year .4: mov ecx,100 cdq idiv ecx test edx,edx jz .100 cmp edx,edx retn ; 24% : ZF=1, leap year .100: test eax,11b retn ; 1% : ZF=?, leap year if EAX%400=0 ``` ## XLISP ```xlisp (DEFUN LEAP-YEARP (YEAR) (AND (= (MOD YEAR 4) 0) (OR (/= (MOD YEAR 100) 0) (= (MOD YEAR 400) 0)))) ; Test the function (DISPLAY (MAPCAR LEAP-YEARP '(1600 1640 1800 1928 1979 1990 2000 2004 2005 2016))) ``` {{out}} ```txt (#T #T () #T () () #T #T () #T) ``` ## XPL0 ```XPL0 func LeapYear(Y); \Return 'true' if Y is a leap year int Y; [if rem(Y/100)=0 then return rem(Y/400)=0; return rem(Y/4)=0; ]; ``` ## Yorick This solution is vectorized and can be applied to scalar or array input. ```yorick func is_leap(y) { return ((y % 4 == 0) & (y % 100 != 0)) | (y % 400 == 0); } ``` Interactive example usage: ```txt > is_leap(1988) 1 > is_leap([1988,1989,1900,2000]) [1,0,0,1] ``` ## zkl ```zkl Time.Date.isLeapYear(1988) //-->True T(1988,1989,1900,2000).apply(Time.Date.isLeapYear) //-->L(True,False,False,True) ``` {{omit from|GUISS|Only the operator can read the calendar}}