Find the greatest common divisor of two integers.
360 Assembly
Translated from FORTRAN.
For maximum compatibility, this program uses only the basic instruction set (S/360) with 2 ASSIST macros (XDECO,XPRNT).
* Greatest common divisor 04/05/2016
GCD CSECT
USING GCD,R15 use calling register
L R6,A u=a
L R7,B v=b
LOOPW LTR R7,R7 while v<>0
BZ ELOOPW leave while
LR R8,R6 t=u
LR R6,R7 u=v
LR R4,R8 t
SRDA R4,32 shift to next reg
DR R4,R7 t/v
LR R7,R4 v=mod(t,v)
B LOOPW end while
ELOOPW LPR R9,R6 c=abs(u)
L R1,A a
XDECO R1,XDEC edit a
MVC PG+4(5),XDEC+7 move a to buffer
L R1,B b
XDECO R1,XDEC edit b
MVC PG+10(5),XDEC+7 move b to buffer
XDECO R9,XDEC edit c
MVC PG+17(5),XDEC+7 move c to buffer
XPRNT PG,80 print buffer
XR R15,R15 return code =0
BR R14 return to caller
A DC F'1071' a
B DC F'1029' b
PG DC CL80'gcd(00000,00000)=00000' buffer
XDEC DS CL12 temp for edit
YREGS
END GCD
Output:
gcd( 1071, 1029)= 21
8th
: gcd \ a b -- gcd
dup 0 n:= if drop ;; then
tuck \ b a b
n:mod \ b a-mod-b
recurse ;
: demo \ a b --
2dup "GCD of " . . " and " . . " = " . gcd . ;
100 5 demo cr
5 100 demo cr
7 23 demo cr
bye
Output:
GCD of 5 and 100 = 5
GCD of 100 and 5 = 5
GCD of 23 and 7 = 1
ACL2
(include-book "arithmetic-3/floor-mod/floor-mod" :dir :system) (defun gcd$ (x y) (declare (xargs :guard (and (natp x) (natp y)))) (cond ((or (not (natp x)) (< y 0)) nil) ((zp y) x) (t (gcd$ y (mod x y)))))
ActionScript
//Euclidean algorithm function gcd(a:int,b:int):int { var tmp:int; //Swap the numbers so a >= b if(a < b) { tmp = a; a = b; b = tmp; } //Find the gcd while(b != 0) { tmp = a % b; a = b; b = tmp; } return a; }
Ada
with Ada.Text_Io; use Ada.Text_Io;
procedure Gcd_Test is
function Gcd (A, B : Integer) return Integer is
M : Integer := A;
N : Integer := B;
T : Integer;
begin
while N /= 0 loop
T := M;
M := N;
N := T mod N;
end loop;
return M;
end Gcd;
begin
Put_Line("GCD of 100, 5 is" & Integer'Image(Gcd(100, 5)));
Put_Line("GCD of 5, 100 is" & Integer'Image(Gcd(5, 100)));
Put_Line("GCD of 7, 23 is" & Integer'Image(Gcd(7, 23)));
end Gcd_Test;
Output:
GCD of 100, 5 is 5
GCD of 5, 100 is 5
GCD of 7, 23 is 1
Aime
o_integer(gcd(33, 77));
o_byte('\n');
o_integer(gcd(49865, 69811));
o_byte('\n');
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 FORMATted transput}}
PROC gcd = (INT a, b) INT: (
IF a = 0 THEN
b
ELIF b = 0 THEN
a
ELIF a > b THEN
gcd(b, a MOD b)
ELSE
gcd(a, b MOD a)
FI
);
test:(
INT a = 33, b = 77;
printf(($x"The gcd of"g" and "g" is "gl$,a,b,gcd(a,b)));
INT c = 49865, d = 69811;
printf(($x"The gcd of"g" and "g" is "gl$,c,d,gcd(c,d)))
)
Output:
The gcd of +33 and +77 is +11
The gcd of +49865 and +69811 is +9973
ALGOL W
begin
% iterative Greatest Common Divisor routine %
integer procedure gcd ( integer value m, n ) ;
begin
integer a, b, newA;
a := abs( m );
b := abs( n );
if a = 0 then begin
b
end
else begin
while b not = 0 do begin
newA := b;
b := a rem b;
a := newA;
end;
a
end
end gcd ;
write( gcd( -21, 35 ) );
end.
Alore
def gcd(a as Int, b as Int) as Int
while b != 0
a,b = b, a mod b
end
return Abs(a)
end
AntLang
AntLang has a built-in gcd function.
gcd[33; 77]
It is not recommended, but possible to implement it on your own.
/Unoptimized version
gcd':{a:x;b:y;last[{(0 eq a mod x) min (0 eq b mod x)} hfilter {1 + x} map range[a max b]]}
APL
Works with Dyalog APL
33 49865 ∨ 77 69811
11 9973
If you're interested in how you'd write GCD in Dyalog, if Dyalog didn't have a primitive for it, (i.e. using other algorithms mentioned on this page: iterative, recursive, binary recursive), see [http://www.dyalog.com/dfnsdws/n_gcd.htm different ways to write GCD in Dyalog].
Works with APL2
⌈/(^/0=A∘.|X)/A←⍳⌊/X←49865 69811
9973
AppleScript
By recursion:
-- gcd :: Int -> Int -> Int on gcd(a, b) if b ≠ 0 then gcd(b, a mod b) else if a < 0 then -a else a end if end if end gcd
Applesoft BASIC
0 A = ABS(INT(A))
1 B = ABS(INT(B))
2 GCD = A * NOT NOT B
3 FOR B = B + A * NOT B TO 0 STEP 0
4 A = GCD
5 GCD = B
6 B = A - INT (A / GCD) * GCD
7 NEXT B
Arendelle
< a , b >
( r , @a )
[ @r != 0 ,
( r , @a % @b )
{ @r != 0 ,
( a , @b )
( b , @r )
}
]
( return , @b )
Arturo
print $(gcd #(10 15))
Output:
5
AutoHotkey
Contributed by Laszlo on the ahk forum
GCD(a,b) {
Return b=0 ? Abs(a) : Gcd(b,mod(a,b))
}
Significantly faster than recursion:
GCD(a, b) {
while b
b := Mod(a | 0x0, a := b)
return a
}
AutoIt
_GCD(18, 12)
_GCD(1071, 1029)
_GCD(3528, 3780)
Func _GCD($ia, $ib)
Local $ret = "GCD of " & $ia & " : " & $ib & " = "
Local $imod
While True
$imod = Mod($ia, $ib)
If $imod = 0 Then Return ConsoleWrite($ret & $ib & @CRLF)
$ia = $ib
$ib = $imod
WEnd
EndFunc ;==>_GCD
Output:
GCD of 18 : 12 = 6
GCD of 1071 : 1029 = 21
GCD of 3528 : 3780 = 252
AWK
The following scriptlet defines the gcd() function, then reads pairs of numbers from stdin, and reports their gcd on stdout.
$ awk 'function gcd(p,q){return(q?gcd(q,(p%q)):p)}{print gcd($1,$2)}'
12 16
4
22 33
11
45 67
1
Axe
Lbl GCD
r₁→A
r₂→B
!If B
A
Return
End
GCD(B,A^B)
Batch File
Recursive method
:: gcd.cmd
@echo off
:gcd
if "%2" equ "" goto :instructions
if "%1" equ "" goto :instructions
if %2 equ 0 (
set final=%1
goto :done
)
set /a res = %1 %% %2
call :gcd %2 %res%
goto :eof
:done
echo gcd=%final%
goto :eof
:instructions
echo Syntax:
echo GCD {a} {b}
echo.
BASIC
Works with QuickBasic 4.5
Iterative
function gcd(a%, b%)
if a > b then
factor = a
else
factor = b
end if
for l = factor to 1 step -1
if a mod l = 0 and b mod l = 0 then
gcd = l
end if
next l
gcd = 1
end function
Recursive
function gcd(a%, b%)
if a = 0 gcd = b
if b = 0 gcd = a
if a > b gcd = gcd(b, a mod b)
gcd = gcd(a, b mod a)
end function
IS-BASIC
100 DEF GCD(A,B)
110 DO WHILE B>0
120 LET T=B
130 LET B=MOD(A,B)
140 LET A=T
150 LOOP
160 LET GCD=A
170 END DEF
180 PRINT GCD(12,16)
Sinclair ZX81 BASIC
10 LET M=119
20 LET N=544
30 LET R=M-N*INT (M/N)
40 IF R=0 THEN GOTO 80
50 LET M=N
60 LET N=R
70 GOTO 30
80 PRINT N
Output:
17
BBC BASIC
DEF FN_GCD_Iterative_Euclid(A%, B%)
LOCAL C%
WHILE B%
C% = A%
A% = B%
B% = C% MOD B%
ENDWHILE
= ABS(A%)
Bc
Works with GNU bc. Translated from C.
Utility functions:
define even(a)
{
if ( a % 2 == 0 ) {
return(1);
} else {
return(0);
}
}
define abs(a)
{
if (a<0) {
return(-a);
} else {
return(a);
}
}
'''Iterative (Euclid)'''
define gcd_iter(u, v)
{
while(v) {
t = u;
u = v;
v = t % v;
}
return(abs(u));
}
'''Recursive'''
define gcd(u, v)
{
if (v) {
return ( gcd(v, u%v) );
} else {
return (abs(u));
}
}
'''Iterative (Binary)'''
define gcd_bin(u, v)
{
u = abs(u);
v = abs(v);
if ( u < v ) {
t = u; u = v; v = t;
}
if ( v == 0 ) { return(u); }
k = 1;
while (even(u) && even(v)) {
u = u / 2; v = v / 2;
k = k * 2;
}
if ( even(u) ) {
t = -v;
} else {
t = u;
}
while (t) {
while (even(t)) {
t = t / 2;
}
if (t > 0) {
u = t;
} else {
v = -t;
}
t = u - v;
}
return (u * k);
}
Befunge
#v&< @.$<
:<\g05%p05:_^#
Bracmat
Bracmat uses the Euclidean algorithm to simplify fractions.
The den function extracts the denominator from a fraction.
(gcd=a b.!arg:(?a.?b)&!b*den$(!a*!b^-1)^-1);
Example:
{?} gcd$(49865.69811)
{!} 9973
C
Iterative Euclid algorithm
int gcd_iter(int u, int v) { if (u < 0) u = -u; if (v < 0) v = -v; if (v) while ((u %= v) && (v %= u)); return (u + v); }
Recursive Euclid algorithm
int gcd(int u, int v) { return (v != 0)?gcd(v, u%v):u; }
Iterative binary algorithm
int gcd_bin(int u, int v) { int t, k; u = u < 0 ? -u : u; /* abs(u) */ v = v < 0 ? -v : v; if (u < v) { t = u; u = v; v = t; } if (v == 0) return u; k = 1; while (u & 1 == 0 && v & 1 == 0) { /* u, v - even */ u >>= 1; v >>= 1; k <<= 1; } t = (u & 1) ? -v : u; while (t) { while (t & 1 == 0) t >>= 1; if (t > 0) u = t; else v = -t; t = u - v; } return u * k; }
C++
#include <iostream #include <numeric> int main() { std::cout << "The greatest common divisor of 12 and 18 is " << std::gcd(12, 18) << " !\n"; }
#include <boost/math/common_factor.hpp> #include <iostream> int main() { std::cout << "The greatest common divisor of 12 and 18 is " << boost::math::gcd(12, 18) << "!\n"; }
Output:
The greatest common divisor of 12 and 18 is 6!
C#
Iterative
static void Main() { Console.WriteLine("GCD of {0} and {1} is {2}", 1, 1, gcd(1, 1)); Console.WriteLine("GCD of {0} and {1} is {2}", 1, 10, gcd(1, 10)); Console.WriteLine("GCD of {0} and {1} is {2}", 10, 100, gcd(10, 100)); Console.WriteLine("GCD of {0} and {1} is {2}", 5, 50, gcd(5, 50)); Console.WriteLine("GCD of {0} and {1} is {2}", 8, 24, gcd(8, 24)); Console.WriteLine("GCD of {0} and {1} is {2}", 36, 17, gcd(36, 17)); Console.WriteLine("GCD of {0} and {1} is {2}", 36, 18, gcd(36, 18)); Console.WriteLine("GCD of {0} and {1} is {2}", 36, 19, gcd(36, 19)); for (int x = 1; x < 36; x++) { Console.WriteLine("GCD of {0} and {1} is {2}", 36, x, gcd(36, x)); } Console.Read(); } /// <summary> /// Greatest Common Denominator using Euclidian Algorithm /// </summary> static int gcd(int a, int b) { while (b != 0) b = a % (a = b); return a; }
Example output:
GCD of 1 and 1 is 1
GCD of 1 and 10 is 1
GCD of 10 and 100 is 10
GCD of 5 and 50 is 5
GCD of 8 and 24 is 8
GCD of 36 and 1 is 1
GCD of 36 and 2 is 2
..
GCD of 36 and 16 is 4
GCD of 36 and 17 is 1
GCD of 36 and 18 is 18
..
..
GCD of 36 and 33 is 3
GCD of 36 and 34 is 2
GCD of 36 and 35 is 1
Recursive
static void Main(string[] args) { Console.WriteLine("GCD of {0} and {1} is {2}", 1, 1, gcd(1, 1)); Console.WriteLine("GCD of {0} and {1} is {2}", 1, 10, gcd(1, 10)); Console.WriteLine("GCD of {0} and {1} is {2}", 10, 100, gcd(10, 100)); Console.WriteLine("GCD of {0} and {1} is {2}", 5, 50, gcd(5, 50)); Console.WriteLine("GCD of {0} and {1} is {2}", 8, 24, gcd(8, 24)); Console.WriteLine("GCD of {0} and {1} is {2}", 36, 17, gcd(36, 17)); Console.WriteLine("GCD of {0} and {1} is {2}", 36, 18, gcd(36, 18)); Console.WriteLine("GCD of {0} and {1} is {2}", 36, 19, gcd(36, 19)); for (int x = 1; x < 36; x++) { Console.WriteLine("GCD of {0} and {1} is {2}", 36, x, gcd(36, x)); } Console.Read(); } // Greatest Common Denominator using Euclidian Algorithm // Gist: https://gist.github.com/SecretDeveloper/6c426f8993873f1a05f7 static int gcd(int a, int b) { return b==0 ? a : gcd(b, a % b); }
Example output:
GCD of 1 and 1 is 1
GCD of 1 and 10 is 1
GCD of 10 and 100 is 10
GCD of 5 and 50 is 5
GCD of 8 and 24 is 8
GCD of 36 and 1 is 1
GCD of 36 and 2 is 2
..
GCD of 36 and 16 is 4
GCD of 36 and 17 is 1
GCD of 36 and 18 is 18
..
..
GCD of 36 and 33 is 3
GCD of 36 and 34 is 2
GCD of 36 and 35 is 1
Clojure
Euclid's Algorithm
(defn gcd "(gcd a b) computes the greatest common divisor of a and b." [a b] (if (zero? b) a (recur b (mod a b))))
That recur call is the same as (gcd b (mod a b)),
but makes use of Clojure's explicit tail call optimization.
This can be easily extended to work with variadic arguments:
(defn gcd* "greatest common divisor of a list of numbers" [& lst] (reduce gcd lst))
Stein's Algorithm (Binary GCD)
(defn stein-gcd [a b] (cond (zero? a) b (zero? b) a (and (even? a) (even? b)) (* 2 (stein-gcd (unsigned-bit-shift-right a 1) (unsigned-bit-shift-right b 1))) (and (even? a) (odd? b)) (recur (unsigned-bit-shift-right a 1) b) (and (odd? a) (even? b)) (recur a (unsigned-bit-shift-right b 1)) (and (odd? a) (odd? b)) (recur (unsigned-bit-shift-right (Math/abs (- a b)) 1) (min a b))))
COBOL
IDENTIFICATION DIVISION.
PROGRAM-ID. GCD.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 A PIC 9(10) VALUE ZEROES.
01 B PIC 9(10) VALUE ZEROES.
01 TEMP PIC 9(10) VALUE ZEROES.
PROCEDURE DIVISION.
Begin.
DISPLAY "Enter first number, max 10 digits."
ACCEPT A
DISPLAY "Enter second number, max 10 digits."
ACCEPT B
IF A < B
MOVE B TO TEMP
MOVE A TO B
MOVE TEMP TO B
END-IF
PERFORM UNTIL B = 0
MOVE A TO TEMP
MOVE B TO A
DIVIDE TEMP BY B GIVING TEMP REMAINDER B
END-PERFORM
DISPLAY "The gcd is " A
STOP RUN.
Cobra
class Rosetta
def gcd(u as number, v as number) as number
u, v = u.abs, v.abs
while v > 0
u, v = v, u % v
return u
def main
print "gcd of [12] and [8] is [.gcd(12, 8)]"
print "gcd of [12] and [-8] is [.gcd(12, -8)]"
print "gcd of [96] and [27] is [.gcd(27, 96)]"
print "gcd of [51] and [34] is [.gcd(34, 51)]"
Output:
gcd of 12 and 8 is 4
gcd of 12 and -8 is 4
gcd of 96 and 27 is 3
gcd of 51 and 34 is 17
CoffeeScript
Simple recursion
gcd = (x, y) ->
if y == 0 then x else gcd y, x % y
Since JS has no TCO, here's a version with no recursion
gcd = (x, y) ->
[1..(Math.min x, y)].reduce (acc, v) ->
if x % v == 0 and y % v == 0 then v else acc
Common Lisp
Common Lisp provides a ''gcd'' function.
CL-USER> (gcd 2345 5432) 7
Here is an implementation using the do macro.
We call the function gcd* so as not to conflict with common-lisp:gcd.
(defun gcd* (a b) (do () ((zerop b) (abs a)) (shiftf a b (mod a b))))
Here is a tail-recursive implementation.
(defun gcd* (a b) (if (zerop b) a (gcd2 b (mod a b))))
The last implementation is based on the loop macro.
(defun gcd* (a b) (loop for x = a then y and y = b then (mod x y) until (zerop y) finally (return x)))
Component Pascal
BlackBox Component Builder
MODULE Operations;
IMPORT StdLog,Args,Strings;
PROCEDURE Gcd(a,b: LONGINT):LONGINT;
VAR
r: LONGINT;
BEGIN
LOOP
r := a MOD b;
IF r = 0 THEN RETURN b END;
a := b;b := r
END
END Gcd;
PROCEDURE DoGcd*;
VAR
x,y,done: INTEGER;
p: Args.Params;
BEGIN
Args.Get(p);
IF p.argc >= 2 THEN
Strings.StringToInt(p.args[0],x,done);
Strings.StringToInt(p.args[1],y,done);
StdLog.String("gcd("+p.args[0]+","+p.args[1]+")=");StdLog.Int(Gcd(x,y));StdLog.Ln
END
END DoGcd;
END Operations.
Execute:
^Q Operations.DoGcd 12 8 ~
^Q Operations.DoGcd 100 5 ~
^Q Operations.DoGcd 7 23 ~
^Q Operations.DoGcd 24 -112 ~
Output:
gcd(12 ,8 )= 4
gcd(100 ,5 )= 5
gcd(7 ,23 )= 1
gcd(24 ,-112 )= -8
D
import std.stdio, std.numeric; long myGCD(in long x, in long y) pure nothrow @nogc { if (y == 0) return x; return myGCD(y, x % y); } void main() { gcd(15, 10).writeln; // From Phobos. myGCD(15, 10).writeln; }
Output:
5
5
Dc
[dSa%Lard0<G]dsGx+
This code assumes that there are two integers on the stack.
dc -e'28 24 [dSa%Lard0<G]dsGx+ p'
Delphi
See [[#Pascal / Delphi / Free Pascal]].
DWScript
PrintLn(Gcd(231, 210));
Output:
21
Dyalect
Translated from Go.
func gcd(a, b) {
func bgcd(a, b, res) {
if a == b {
return res * a
} else if a % 2 == 0 && b % 2 == 0 {
return bgcd(a/2, b/2, 2*res)
} else if a % 2 == 0 {
return bgcd(a/2, b, res)
} else if b % 2 == 0 {
return bgcd(a, b/2, res)
} else if a > b {
return bgcd(a-b, b, res)
} else {
return bgcd(a, b-a, res)
}
}
return bgcd(a, b, 1)
}
var testdata = [
(a: 33, b: 77),
(a: 49865, b: 69811)
]
for v in testdata {
print("gcd(\(v.a), \(v.b)) = \(gcd(v.a, v.b))")
}
Output:
gcd(33, 77) = 11
gcd(49865, 69811) = 9973
E
Translated from Python.
def gcd(var u :int, var v :int) {
while (v != 0) {
def r := u %% v
u := v
v := r
}
return u.abs()
}
EasyLang
func gcd a b . res .
while b <> 0
h = b
b = a mod b
a = h
.
res = a
.
call gcd 120 35 r
print r
EDSAC order code
The EDSAC had no built-in division. For this task, a subroutine is needed to return A mod B, where A and B are positive 35-bit integers. The rest of the program is fairly straightforward.
[Greatest common divisor for RosettaGit.
Program for EDSAC, Initial Orders 2]
[Set up pairs of integers for demo]
T 45 K [store address in location 45;
values are then accessed by code letter H]
P 220 F [<------ address here]
[Library subroutine R2. Reads positive integers during input of orders,
and is then overwritten (so doesn't take up any memory).
Each integer is followed by 'F', except the last is followed by '#TZ'.]
GKT20FVDL8FA40DUDTFI40FA40FS39FG@S2FG23FA5@T5@E4@E13Z
T #H [Tell R2 the storage location defined above
Integers to be read by R2. First item is count, then pairs for GCD algo.]
4F1066F2019F1815F1914F103785682F167928761F109876463F177777648#TZ
[----------------------------------------------------------------------
Library subroutine P7.
Prints long strictly positive integer at 0D.
10 characters, right justified, padded left with spaces.
Closed, even; 35 storage locations; working position 4D.]
T 56 K
GKA3FT26@H28#@NDYFLDT4DS27@TFH8@S8@T1FV4DAFG31@SFLDUFOFFFSFL4F
T4DA1FA27@G11@XFT28#ZPFT27ZP1024FP610D@524D!FO30@SFL8FE22@
[----------------------------------------------------------------------
Subroutine to return a mod b, where a and b are
positive 35-bit integers (maximum 2^34 - 1).
Input: a at 4D, b at 6D.
Output: a mod b at 4D; does not change 6D.
Working location 0D.]
T 100 K
G K
A 3 F [plant link]
T 26 @
A 6 D [load divisor]
[3] T D [initialize shifted divisor]
A 4 D [load dividend]
R D [shift 1 right]
S D [shifted divisor > dividend/2 yet?]
G 12 @ [yes, start subtraction]
T 27 @ [no, clear acc]
A D [shift divisor 1 more]
L D
E 3 @ [loop back (always, since acc = 0)]
[12] T 27 @ [clear acc]
[13] A 4 D [load remainder (initially = dividend)]
S D [trial subtraction]
G 17 @ [skip if can't subtract]
T 4 D [update remainder]
[17] T 27 @ [clear acc]
A 6 D [load original divisor]
S D [is shifted divisor back to original?]
E 26 @ [yes, exit (with accumulator = 0,
in accordance with EDSAC convention)]
T 27 @ [no, clear acc]
A D [shift divisor 1 right]
R D
T D
E 13 @ [loop back (always, since acc = 0)]
[26] E F
[27] P F [junk word, to clear accumulator]
[----------------------------------------------------------------------
Subroutine to find GCD of two positive integers at 4D and 6D.
Returns result in 6D.]
T 130 K
G K
A 3 F [plant link]
T 12 @
[2] A 2 @ [set up return from subroutine]
G 100 F [4D := 4D mod 6D]
S 4 D [load negative of 4D]
E 12 @ [exit if 4D = 0]
T D [else swap with 6D, using 0D as temp store]
A 6 D
T 4 D
S D [change back to positive]
T 6 D
E 2 @ [loop back (always, since acc = 0)]
[12] E F
[----------------------------------------------------------------------
Main routine]
T 150 K
G K
[Variable]
[0] P F
[Constants]
[1] P D [single-word 1]
[2] A 2#H [order to load first number of first pair]
[3] P 2 F [to inc addresses by 2]
[4] # F [figure shift]
[5] K 2048 F [letter shift]
[6] G F [letters to print 'GCD']
[7] C F
[8] D F
[9] V F [equals sign (in firures mode)]
[10] ! F [space]
[11] @ F [carriage return]
[12] & F [line feed]
[13] K 4096 F [null char]
[Enter here with acc = 0]
[14] O 4 @ [set teleprinter to figures]
S H [negative of number of pairs]
T @ [initialize counter]
A 2 @ [initial load order]
[18] U 23 @ [plant order to load 1st integer]
U 32 @
A 3 @ [inc address by 2]
U 28 @ [plant order to load 2nd integer]
T 34 @
[23] A #H [load 1st integer (order set up at runtime)]
T D [to 0D for printing]
A 25 @ [for return from print subroutine]
G 56 F [print 1st number]
O 10 @ [followed by space]
[28] A #H [load 2nd integer (order set up at runtime)]
T D [to 0D for printing]
A 30 @ [for return from print subroutine]
G 56 F [print 2nd number]
[32] A #H [load 1st integer (order set up at runtime)]
T 4 D [to 4D for GCD subroutine]
[34] A #H [load 2nd integer (order set up at runtime)]
T 6 D [to 4D for GCD subroutine]
[36] A 36 @ [for return from subroutine]
G 130 F [call subroutine for GCD]
[Cosmetic printing, add ' GCD = ']
O 10 @
O 10 @
O 5 @
O 6 @
O 7 @
O 8 @
O 4 @
O 10 @
O 9 @
O 10 @
A 6 D [load GCD]
T D [to 0D for printing]
A 50 @ [for return from print subroutine]
G 56 F [print GCD]
O 11 @ [followed by new line]
O 12 @
[On to next pair]
A @ [load negative count of pairs]
A 1 @ [add 1]
E 62 @ [exit if count = 0]
T @ [store back]
A 23 @ [order to load first of pair]
A 3 @ [inc address by 4 for next pair]
A 3 @
G 18 @ [loop back (always, since 'A' < 0)]
[62] O 13 @ [null char to flush teleprinter buffer]
Z F [stop]
E 14 Z [define entry point]
P F [acc = 0 on entry]
Output:
1066 2019 GCD = 1
1815 1914 GCD = 33
103785682 167928761 GCD = 1001
109876463 177777648 GCD = 1234567
Eiffel
Translated from D.
class
APPLICATION
create
make
feature -- Implementation
gcd (x: INTEGER y: INTEGER): INTEGER
do
if y = 0 then
Result := x
else
Result := gcd (y, x \\ y);
end
end
feature {NONE} -- Initialization
make
-- Run application.
do
print (gcd (15, 10))
print ("%N")
end
end
Elena
Translated from C#.
ELENA 4.x :
import system'math;
import extensions;
gcd(a,b)
{
var i := a;
var j := b;
while(j != 0)
{
var tmp := i;
i := j;
j := tmp.mod(j)
};
^ i
}
printGCD(a,b)
{
console.printLineFormatted("GCD of {0} and {1} is {2}", a, b, gcd(a,b))
}
public program()
{
printGCD(1,1);
printGCD(1,10);
printGCD(10,100);
printGCD(5,50);
printGCD(8,24);
printGCD(36,17);
printGCD(36,18);
printGCD(36,19);
printGCD(36,33);
}
Output:
GCD of 1 and 1 is 1
GCD of 1 and 10 is 1
GCD of 10 and 100 is 10
GCD of 5 and 50 is 5
GCD of 8 and 24 is 8
GCD of 36 and 17 is 1
GCD of 36 and 18 is 18
GCD of 36 and 19 is 1
GCD of 36 and 33 is 3
Elixir
defmodule RC do def gcd(a,0), do: abs(a) def gcd(a,b), do: gcd(b, rem(a,b)) end IO.puts RC.gcd(1071, 1029) IO.puts RC.gcd(3528, 3780)
Output:
21
252
Emacs Lisp
(defun gcd (a b) (cond ((< a b) (gcd a (- b a))) ((> a b) (gcd (- a b) b)) (t a)))
Erlang
% Implemented by Arjun Sunel -module(gcd). -export([main/0]). main() ->gcd(-36,4). gcd(A, 0) -> A; gcd(A, B) -> gcd(B, A rem B).
Output:
4
ERRE
This is a iterative version.
PROGRAM EUCLIDE
! calculate G.C.D. between two integer numbers
! using Euclidean algorithm
!VAR J%,K%,MCD%,A%,B%
BEGIN
PRINT(CHR$(12);"Input two numbers : ";) !CHR$(147) in C-64 version
INPUT(J%,K%)
A%=J% B%=K%
WHILE A%<>B% DO
IF A%>B%
THEN
A%=A%-B%
ELSE
B%=B%-A%
END IF
END WHILE
MCD%=A%
PRINT("G.C.D. between";J%;"and";K%;"is";MCD%)
END PROGRAM
Output: Input two numbers : ? 112,44 G.C.D. between 112 and 44 is 4
Euler Math Toolbox
Non-recursive version in Euler Math Toolbox. Note, that there is a built-in command.
>ggt(123456795,1234567851)
33
>function myggt (n:index, m:index) ...
$ if n<m then {n,m}={m,n}; endif;
$ repeat
$ k=mod(n,m);
$ if k==0 then return m; endif;
$ if k==1 then return 1; endif;
$ {n,m}={m,k};
$ end;
$ endfunction
>myggt(123456795,1234567851)
33
Euphoria
Translated from C/C++.
Iterative Euclid algorithm
function gcd_iter(integer u, integer v)
integer t
while v do
t = u
u = v
v = remainder(t, v)
end while
if u < 0 then
return -u
else
return u
end if
end function
Recursive Euclid algorithm
function gcd(integer u, integer v)
if v then
return gcd(v, remainder(u, v))
elsif u < 0 then
return -u
else
return u
end if
end function
Iterative binary algorithm
function gcd_bin(integer u, integer v)
integer t, k
if u < 0 then -- abs(u)
u = -u
end if
if v < 0 then -- abs(v)
v = -v
end if
if u < v then
t = u
u = v
v = t
end if
if v = 0 then
return u
end if
k = 1
while and_bits(u,1) = 0 and and_bits(v,1) = 0 do
u = floor(u/2) -- u >>= 1
v = floor(v/2) -- v >>= 1
k *= 2 -- k <<= 1
end while
if and_bits(u,1) then
t = -v
else
t = u
end if
while t do
while and_bits(t, 1) = 0 do
t = floor(t/2)
end while
if t > 0 then
u = t
else
v = -t
end if
t = u - v
end while
return u * k
end function
Excel
Excel's GCD can handle multiple values. Type in a cell:
=GCD(A1:E1)
This will get the GCD of the first 5 cells of the first row.
30 10 500 25 1000
5
Ezhil
## இந்த நிரல் இரு எண்களுக்கு இடையிலான மீச்சிறு பொது மடங்கு (LCM), மீப்பெரு பொது வகுத்தி (GCD) என்ன என்று கணக்கிடும்
நிரல்பாகம் மீபொவ(எண்1, எண்2)
@(எண்1 == எண்2) ஆனால்
## இரு எண்களும் சமம் என்பதால், அந்த எண்ணேதான் அதன் மீபொவ
பின்கொடு எண்1
@(எண்1 > எண்2) இல்லைஆனால்
சிறியது = எண்2
பெரியது = எண்1
இல்லை
சிறியது = எண்1
பெரியது = எண்2
முடி
மீதம் = பெரியது % சிறியது
@(மீதம் == 0) ஆனால்
## பெரிய எண்ணில் சிறிய எண் மீதமின்றி வகுபடுவதால், சிறிய எண்தான் மீப்பெரு பொதுவகுத்தியாக இருக்கமுடியும்
பின்கொடு சிறியது
இல்லை
தொடக்கம் = சிறியது - 1
நிறைவு = 1
@(எண் = தொடக்கம், எண் >= நிறைவு, எண் = எண் - 1) ஆக
மீதம்1 = சிறியது % எண்
மீதம்2 = பெரியது % எண்
## இரு எண்களையும் மீதமின்றி வகுக்கக்கூடிய பெரிய எண்ணைக் கண்டறிகிறோம்
@((மீதம்1 == 0) && (மீதம்2 == 0)) ஆனால்
பின்கொடு எண்
முடி
முடி
முடி
முடி
அ = int(உள்ளீடு("ஓர் எண்ணைத் தாருங்கள் "))
ஆ = int(உள்ளீடு("இன்னோர் எண்ணைத் தாருங்கள் "))
பதிப்பி "நீங்கள் தந்த இரு எண்களின் மீபொவ (மீப்பெரு பொது வகுத்தி, GCD) = ", மீபொவ(அ, ஆ)
Free Pascal
See [[#Pascal / Delphi / Free Pascal]].
Frege
module gcd.GCD where pure native parseInt java.lang.Integer.parseInt :: String -> Int gcd' a 0 = a gcd' a b = gcd' b (a `mod` b) main args = do (a:b:_) = args println $ gcd' (parseInt a) (parseInt b)
F#
let rec gcd a b = if b = 0 then abs a else gcd b (a % b) >gcd 400 600 val it : int = 200
Factor
: gcd ( a b -- c )
[ abs ] [
[ nip ] [ mod ] 2bi gcd
] if-zero ;
FALSE
10 15$ [0=~][$@$@$@\/*-$]#%. { gcd(10,15)=5 }
Fantom
class Main
{
static Int gcd (Int a, Int b)
{
a = a.abs
b = b.abs
while (b > 0)
{
t := a
a = b
b = t % b
}
return a
}
public static Void main()
{
echo ("GCD of 51, 34 is: " + gcd(51, 34))
}
}
Forth
: gcd ( a b -- n )
begin dup while tuck mod repeat drop ;
Fortran
Works with Fortran 95 and later
Recursive Euclid algorithm
recursive function gcd_rec(u, v) result(gcd)
integer :: gcd
integer, intent(in) :: u, v
if (mod(u, v) /= 0) then
gcd = gcd_rec(v, mod(u, v))
else
gcd = v
end if
end function gcd_rec
Iterative Euclid algorithm
subroutine gcd_iter(value, u, v)
integer, intent(out) :: value
integer, intent(inout) :: u, v
integer :: t
do while( v /= 0 )
t = u
u = v
v = mod(t, v)
enddo
value = abs(u)
end subroutine gcd_iter
A different version, and implemented as function
function gcd(v, t)
integer :: gcd
integer, intent(in) :: v, t
integer :: c, b, a
b = t
a = v
do
c = mod(a, b)
if ( c == 0) exit
a = b
b = c
end do
gcd = b ! abs(b)
end function gcd
Iterative binary algorithm
subroutine gcd_bin(value, u, v)
integer, intent(out) :: value
integer, intent(inout) :: u, v
integer :: k, t
u = abs(u)
v = abs(v)
if( u < v ) then
t = u
u = v
v = t
endif
if( v == 0 ) then
value = u
return
endif
k = 1
do while( (mod(u, 2) == 0).and.(mod(v, 2) == 0) )
u = u / 2
v = v / 2
k = k * 2
enddo
if( (mod(u, 2) == 0) ) then
t = u
else
t = -v
endif
do while( t /= 0 )
do while( (mod(t, 2) == 0) )
t = t / 2
enddo
if( t > 0 ) then
u = t
else
v = -t
endif
t = u - v
enddo
value = u * k
end subroutine gcd_bin
Notes on performance
gcd_iter(40902, 24140) takes us about '''2.8''' µsec
gcd_bin(40902, 24140) takes us about '''2.5''' µsec
FreeBASIC
' version 17-06-2015
' compile with: fbc -s console
Function gcd(x As ULongInt, y As ULongInt) As ULongInt
Dim As ULongInt t
While y
t = y
y = x Mod y
x = t
Wend
Return x
End Function
' ------=< MAIN >=------
Dim As ULongInt a = 111111111111111
Dim As ULongInt b = 11111
Print : Print "GCD(";a;", ";b;") = "; gcd(a, b)
Print : Print "GCD(";a;", 111) = "; gcd(a, 111)
' empty keyboard buffer
While InKey <> "" : Wend
Print : Print : Print "hit any key to end program"
Sleep
End
Output:
GCD(111111111111111, 11111) = 11111
GCD(111111111111111, 111) = 111
Frink
Frink has a builtin gcd[x,y] function
that returns the GCD of two integers (which can be arbitrarily large.)
println[gcd[12345,98765]]
FunL
FunL has pre-defined function gcd in module integers defined as:
def
gcd( 0, 0 ) = error( 'integers.gcd: gcd( 0, 0 ) is undefined' )
gcd( a, b ) =
def
_gcd( a, 0 ) = a
_gcd( a, b ) = _gcd( b, a%b )
_gcd( abs(a), abs(b) )
FutureBasic
local fn gcd( a as long, b as long )
dim as long result
if ( b != 0 )
result = fn gcd( b, a mod b)
else
result = abs(a)
end if
end fn = result
GAP
# Built-in
GcdInt(35, 42);
# 7
# Euclidean algorithm
GcdInteger := function(a, b)
local c;
a := AbsInt(a);
b := AbsInt(b);
while b > 0 do
c := a;
a := b;
b := RemInt(c, b);
od;
return a;
end;
GcdInteger(35, 42);
# 7
Genyris
Recursive
def gcd (u v)
u = (abs u)
v = (abs v)
cond
(equal? v 0) u
else (gcd v (% u v))
Iterative
def gcd (u v)
u = (abs u)
v = (abs v)
while (not (equal? v 0))
var tmp (% u v)
u = v
v = tmp
u
GFA Basic
'
' Greatest Common Divisor
'
a%=24
b%=112
PRINT "GCD of ";a%;" and ";b%;" is ";@gcd(a%,b%)
'
' Function computes gcd
'
FUNCTION gcd(a%,b%)
LOCAL t%
'
WHILE b%<>0
t%=a%
a%=b%
b%=t% MOD b%
WEND
'
RETURN ABS(a%)
ENDFUNC
GML
var n,m,r;
n = max(argument0,argument1);
m = min(argument0,argument1);
while (m != 0)
{
r = n mod m;
n = m;
m = r;
}
return a;
Gnuplot
gcd (a, b) = b == 0 ? a : gcd (b, a % b)
Example:
print gcd (111111, 1111)
Output:
11
Go
Binary Euclidian
package main import "fmt" func gcd(a, b int) int { var bgcd func(a, b, res int) int bgcd = func(a, b, res int) int { switch { case a == b: return res * a case a % 2 == 0 && b % 2 == 0: return bgcd(a/2, b/2, 2*res) case a % 2 == 0: return bgcd(a/2, b, res) case b % 2 == 0: return bgcd(a, b/2, res) case a > b: return bgcd(a-b, b, res) default: return bgcd(a, b-a, res) } } return bgcd(a, b, 1) } func main() { type pair struct { a int b int } var testdata []pair = []pair{ pair{33, 77}, pair{49865, 69811}, } for _, v := range testdata { fmt.Printf("gcd(%d, %d) = %d\n", v.a, v.b, gcd(v.a, v.b)) } }
Output for Binary Euclidian algorithm:
gcd(33, 77) = 11
gcd(49865, 69811) = 9973
Iterative
package main import "fmt" func gcd(x, y int) int { for y != 0 { x, y = y, x%y } return x } func main() { fmt.Println(gcd(33, 77)) fmt.Println(gcd(49865, 69811)) }
Builtin
(This is just a wrapper for big.GCD)
package main import ( "fmt" "math/big" ) func gcd(x, y int64) int64 { return new(big.Int).GCD(nil, nil, big.NewInt(x), big.NewInt(y)).Int64() } func main() { fmt.Println(gcd(33, 77)) fmt.Println(gcd(49865, 69811)) }
Output in either case
11
9973
Groovy
Recursive
def gcdR gcdR = { m, n -> m = m.abs(); n = n.abs(); n == 0 ? m : m%n == 0 ? n : gcdR(n, m%n) }
Iterative
def gcdI = { m, n -> m = m.abs(); n = n.abs(); n == 0 ? m : { while(m%n != 0) { t=n; n=m%n; m=t }; n }() }
Test program:
println " R I" println "gcd(28, 0) = ${gcdR(28, 0)} == ${gcdI(28, 0)}" println "gcd(0, 28) = ${gcdR(0, 28)} == ${gcdI(0, 28)}" println "gcd(0, -28) = ${gcdR(0, -28)} == ${gcdI(0, -28)}" println "gcd(70, -28) = ${gcdR(70, -28)} == ${gcdI(70, -28)}" println "gcd(70, 28) = ${gcdR(70, 28)} == ${gcdI(70, 28)}" println "gcd(28, 70) = ${gcdR(28, 70)} == ${gcdI(28, 70)}" println "gcd(800, 70) = ${gcdR(800, 70)} == ${gcdI(800, 70)}" println "gcd(27, -70) = ${gcdR(27, -70)} == ${gcdI(27, -70)}"
Output:
R I
gcd(28, 0) = 28 == 28
gcd(0, 28) = 28 == 28
gcd(0, -28) = 28 == 28
gcd(70, -28) = 14 == 14
gcd(70, 28) = 14 == 14
gcd(28, 70) = 14 == 14
gcd(800, 70) = 10 == 10
gcd(27, -70) = 1 == 1
Haskell
That is already available as the function gcd in the Prelude.
Here's the implementation:
gcd :: (Integral a) => a -> a -> a gcd x y = gcd_ (abs x) (abs y) where gcd_ a 0 = a gcd_ a b = gcd_ b (a `rem` b)
HicEst
FUNCTION gcd(a, b)
IF(b == 0) THEN
gcd = ABS(a)
ELSE
aa = a
gcd = b
DO i = 1, 1E100
r = ABS(MOD(aa, gcd))
IF( r == 0 ) RETURN
aa = gcd
gcd = r
ENDDO
ENDIF
END
Icon and Unicon
link numbers # gcd is part of the Icon Programming Library
procedure main(args)
write(gcd(arg[1], arg[2])) | "Usage: gcd n m")
end
numbers implements this as:
procedure gcd(i,j) #: greatest common divisor
local r
if (i | j) < 1 then runerr(501)
repeat {
r := i % j
if r = 0 then return j
i := j
j := r
}
end
J
x+.y
For example:
12 +. 30
6
Note that +. is a single, two character token.
GCD is a primitive in J (and anyone that has studied
the right kind of mathematics should instantly recognize
why the same operation is used for both GCD and OR -- among other things,
GCD and boolean OR both have the same identity element:
0, and of course they produce the same numeric results on the same arguments
(when we are allowed to use the usual 1 bit implementation
of 0 and 1 for false and true) -
more than that, though,
GCD corresponds to George Boole's original "Boolean Algebra"
(as it was later called).
The redefinition of "Boolean algebra" to include logical negation
came much later, in the 20th century).
gcd could also be defined recursively, if you do not mind a little inefficiency:
gcd=: (| gcd [)^:(0<[)&|
Java
Iterative
public static long gcd(long a, long b){ long factor= Math.min(a, b); for(long loop= factor;loop > 1;loop--){ if(a % loop == 0 && b % loop == 0){ return loop; } } return 1; }
Iterative Euclid's Algorithm
public static int gcd(int a, int b) //valid for positive integers. { while(b > 0) { int c = a % b; a = b; b = c; } return a; }
Optimized Iterative
static int gcd(int a,int b) { int min=a>b?b:a,max=a+b-min, div=min; for(int i=1;i<min;div=min/++i) if(min%div==0&&max%div==0) return div; return 1; }
Iterative binary algorithm
Translated from C/C++.
public static long gcd(long u, long v){ long t, k; if (v == 0) return u; u = Math.abs(u); v = Math.abs(v); if (u < v){ t = u; u = v; v = t; } for(k = 1; (u & 1) == 0 && (v & 1) == 0; k <<= 1){ u >>= 1; v >>= 1; } t = (u & 1) != 0 ? -v : u; while (t != 0){ while ((t & 1) == 0) t >>= 1; if (t > 0) u = t; else v = -t; t = u - v; } return u * k; }
Recursive
public static long gcd(long a, long b){ if(a == 0) return b; if(b == 0) return a; if(a > b) return gcd(b, a % b); return gcd(a, b % a); }
Built-in
import java.math.BigInteger; public static long gcd(long a, long b){ return BigInteger.valueOf(a).gcd(BigInteger.valueOf(b)).longValue(); }
JavaScript
Iterative implementation:
function gcd(a,b) { a = Math.abs(a); b = Math.abs(b); if (b > a) { var temp = a; a = b; b = temp; } while (true) { a %= b; if (a === 0) { return b; } b %= a; if (b === 0) { return a; } } }
Recursive:
function gcd_rec(a, b) { return b ? gcd_rec(b, a % b) : Math.abs(a); }
Implementation that works on an array of integers:
function GCD(arr) { var i, y, n = arr.length, x = Math.abs(arr[0]); for (i = 1; i < n; i++) { y = Math.abs(arr[i]); while (x && y) { (x > y) ? x %= y : y %= x; } x += y; } return x; } //For example: GCD([57,0,-45,-18,90,447]); //=> 3
Joy
DEFINE gcd == [0
] [dup rollup rem] while pop.
jq
def recursive_gcd(a; b):
if b == 0 then a
else recursive_gcd(b; a % b)
end ;
Recent versions of jq include support for tail recursion optimization for arity-0 filters (which can be thought of as arity-1 functions), so here is an implementation that takes advantage of that optimization. Notice that the subfunction, rgcd, can be easily derived from recursive_gcd above by moving the arguments to the input:
def gcd(a; b):
# The subfunction expects [a,b] as input
# i.e. a ~ .[0] and b ~ .[1]
def rgcd: if .[1] == 0 then .[0]
else [.[1], .[0] % .[1]] | rgcd
end;
[a,b] | rgcd ;
Julia
Julia includes a built-in gcd function:
julia> gcd(4,12)
4
julia> gcd(6,12)
6
julia> gcd(7,12)
1
The actual implementation of this function in Julia 0.2's standard library is reproduced here:
function gcd{T<:Integer}(a::T, b::T) neg = a < 0 while b != 0 t = b b = rem(a, b) a = t end g = abs(a) neg ? -g : g end
For arbitrary-precision integers, Julia calls a different implementation from the GMP library.
K
gcd:{:[~x;y;_f[y;x!y]]}
Klong
gcd::{:[~x;y:|~y;x:|x>y;.f(y;x!y);.f(x;y!x)]}
Kotlin
Recursive one line solution:
fun gcd(a: Int, b: Int): Int = if (b == 0) a else gcd(b, a % b)
LabVIEW
Translated from AutoHotkey.
It may be helpful to read about Recursion in LabVIEW.
[[File:LabVIEW Greatest common divisor.png]]
LFE
Translated from Clojure.
> (defun gcd "Get the greatest common divisor." ((a 0) a) ((a b) (gcd b (rem a b))))
Usage:
> (gcd 12 8)
4
> (gcd 12 -8)
4
> (gcd 96 27)
3
> (gcd 51 34)
17
Liberty BASIC
'iterative Euclid algorithm
print GCD(-2,16)
end
function GCD(a,b)
while b
c = a
a = b
b = c mod b
wend
GCD = abs(a)
end function
Limbo
gcd(x: int, y: int): int
{
if(y == 0)
return x;
return gcd(y, x % y);
}
LiveCode
function gcd x,y
repeat until y = 0
put x mod y into z
put y into x
put z into y
end repeat
return x
end gcd
Logo
to gcd :a :b
if :b = 0 [output :a]
output gcd :b modulo :a :b
end
Lua
Translated from C.
function gcd(a,b) if b ~= 0 then return gcd(b, a % b) else return math.abs(a) end end function demo(a,b) print("GCD of " .. a .. " and " .. b .. " is " .. gcd(a, b)) end demo(100, 5) demo(5, 100) demo(7, 23)
Output:
GCD of 100 and 5 is 5
GCD of 5 and 100 is 5
GCD of 7 and 23 is 1
Faster iterative solution of Euclid:
function gcd(a,b) while b~=0 do a,b=b,a%b end return math.abs(a) end
Lucid
dataflow algorithm
gcd(n,m) where
z = [% n, m %] fby if x > y then [% x - y, y %] else [% x, y - x%] fi;
x = hd(z);
y = hd(tl(z));
gcd(n, m) = (x asa x*y eq 0) fby eod;
end
Luck
function gcd(a: int, b: int): int = (
if a==0 then b
else if b==0 then a
else if a>b then gcd(b, a % b)
else gcd(a, b % a)
)
M2000 Interpreter
gcd=lambda (u as long, v as long) -> {
=if(v=0&->abs(u), lambda(v, u mod v))
}
gcd_Iterative= lambda (m as long, n as long) -> {
while m {
let old_m = m
m = n mod m
n = old_m
}
=abs(n)
}
Module CheckGCD (f){
Print f(49865, 69811)=9973
Def ExpType$(x)=Type$(x)
Print ExpType$(f(49865, 69811))="Long"
}
CheckGCD gcd
CheckGCD gcd_Iterative
Maple
To compute the greatest common divisor of two integers in Maple, use the procedure igcd.
igcd( a, b )
For example,
> igcd( 24, 15 );
3
Mathematica / Wolfram Language
GCD[a, b]
MATLAB
function [gcdValue] = greatestcommondivisor(integer1, integer2) gcdValue = gcd(integer1, integer2);
Maxima
/* There is a function gcd(a, b) in Maxima, but one can rewrite it */
gcd2(a, b) := block([a: abs(a), b: abs(b)], while b # 0 do [a, b]: [b, mod(a, b)], a)$
/* both will return 2^97 * 3^48 */
gcd(100!, 6^100), factor;
gcd2(100!, 6^100), factor;
MAXScript
Iterative Euclid algorithm
fn gcdIter a b =
(
while b > 0 do
(
c = mod a b
a = b
b = c
)
abs a
)
Recursive Euclid algorithm
fn gcdRec a b =
(
if b > 0 then gcdRec b (mod a b) else abs a
)
Mercury
Recursive Euclid algorithm
:- module gcd.
:- interface.
:- import_module integer.
:- func gcd(integer, integer) = integer.
:- implementation.
:- pragma memo(gcd/2).
gcd(A, B) = (if B = integer(0) then A else gcd(B, A mod B)).
An example console program to demonstrate the gcd module:
:- module test_gcd.
:- interface.
:- import_module io.
:- pred main(io::di, io::uo) is det.
:- implementation.
:- import_module char.
:- import_module gcd.
:- import_module integer.
:- import_module list.
:- import_module string.
main(!IO) :-
command_line_arguments(Args, !IO),
filter(is_all_digits, Args, CleanArgs),
Arg1 = list.det_index0(CleanArgs, 0),
Arg2 = list.det_index0(CleanArgs, 1),
A = integer.det_from_string(Arg1),
B = integer.det_from_string(Arg2),
Fmt = integer.to_string,
GCD = gcd(A, B),
io.format("gcd(%s, %s) = %s\n", [s(Fmt(A)), s(Fmt(B)), s(Fmt(GCD))], !IO).
Example output:
gcd(70000000000000000000000, 60000000000000000000000000) = 10000000000000000000000
MINIL
// Greatest common divisor
00 0E GCD: ENT R0
01 1E ENT R1
02 21 Again: R2 = R1
03 10 Loop: R1 = R0
04 02 R0 = R2
05 2D Minus: DEC R2
06 8A JZ Stop
07 1D DEC R1
08 C5 JNZ Minus
09 83 JZ Loop
0A 1D Stop: DEC R1
0B C2 JNZ Again
0C 80 JZ GCD // Display GCD in R0
MIPS Assembly
gcd:
# a0 and a1 are the two integer parameters
# return value is in v0
move $t0, $a0
move $t1, $a1
loop:
beq $t1, $0, done
div $t0, $t1
move $t0, $t1
mfhi $t1
j loop
done:
move $v0, $t0
jr $ra
МК-61/52
ИПA ИПB / П9 КИП9 ИПA ИПB ПA ИП9 *
- ПB x=0 00 ИПA С/П
Enter: n = РA, m = РB (n > m).
ML
mLite
fun gcd (a, 0) = a | (0, b) = b | (a, b) where (a < b) = gcd (a, b rem a) | (a, b) = gcd (b, a rem b)
Standard ML
fun gcd a 0 = a
| gcd a b = gcd b (a mod b)
Modula-2
MODULE ggTkgV;
FROM InOut IMPORT ReadCard, WriteCard, WriteLn, WriteString, WriteBf;
VAR x, y, u, v : CARDINAL;
BEGIN
WriteString ("x = "); WriteBf; ReadCard (x);
WriteString ("y = "); WriteBf; ReadCard (y);
u := x;
v := y;
WHILE x # y DO
(* ggT (x, y) = ggT (x0, y0), x * v + y * u = 2 * x0 * y0 *)
IF x > y THEN
x := x - y;
u := u + v
ELSE
y := y - x;
v := v + u
END
END;
WriteString ("ggT ="); WriteCard (x, 6); WriteLn;
WriteString ("kgV ="); WriteCard ((u+v) DIV 2, 6); WriteLn;
WriteString ("u ="); WriteCard (u, 6); WriteLn;
WriteString ("v ="); WriteCard (v , 6); WriteLn
END ggTkgV.
Producing the output:
jan@Beryllium:~/modula/Wirth/PIM$ ggtkgv
x = 12
y = 20
ggT = 4
kgV = 60
u = 44
v = 76
jan@Beryllium:~/modula/Wirth/PIM$ ggtkgv
x = 123
y = 255
ggT = 3
kgV = 10455
u = 13773
v = 7137
Modula-3
MODULE GCD EXPORTS Main;
IMPORT IO, Fmt;
PROCEDURE GCD(a, b: CARDINAL): CARDINAL =
BEGIN
IF a = 0 THEN
RETURN b;
ELSIF b = 0 THEN
RETURN a;
ELSIF a > b THEN
RETURN GCD(b, a MOD b);
ELSE
RETURN GCD(a, b MOD a);
END;
END GCD;
BEGIN
IO.Put("GCD of 100, 5 is " & Fmt.Int(GCD(100, 5)) & "\n");
IO.Put("GCD of 5, 100 is " & Fmt.Int(GCD(5, 100)) & "\n");
IO.Put("GCD of 7, 23 is " & Fmt.Int(GCD(7, 23)) & "\n");
END GCD.
Output:
GCD of 100, 5 is 5
GCD of 5, 100 is 5
GCD of 7, 23 is 1
MUMPS
GCD(A,B)
QUIT:((A/1)'=(A\1))!((B/1)'=(B\1)) 0
SET:A<0 A=-A
SET:B<0 B=-B
IF B'=0
FOR SET T=A#B,A=B,B=T QUIT:B=0 ;ARGUEMENTLESS FOR NEEDS TWO SPACES
QUIT A
Ouput:
CACHE>S X=$$GCD^ROSETTA(12,24) W X
12
CACHE>S X=$$GCD^ROSETTA(24,-112) W X
8
CACHE>S X=$$GCD^ROSETTA(24,-112.2) W X
0
MySQL
DROP FUNCTION IF EXISTS gcd;
DELIMITER |
CREATE FUNCTION gcd(x INT, y INT)
RETURNS INT
BEGIN
SET @dividend=GREATEST(ABS(x),ABS(y));
SET @divisor=LEAST(ABS(x),ABS(y));
IF @divisor=0 THEN
RETURN @dividend;
END IF;
SET @gcd=NULL;
SELECT gcd INTO @gcd FROM
(SELECT @tmp:=@dividend,
@dividend:=@divisor AS gcd,
@divisor:=@tmp % @divisor AS remainder
FROM mysql.help_relation WHERE @divisor>0) AS x
WHERE remainder=0;
RETURN @gcd;
END;|
DELIMITER ;
SELECT gcd(12345, 9876);
+------------------+
| gcd(12345, 9876) |
+------------------+
| 2469 |
+------------------+
1 row in set (0.00 sec)
NetRexx
/* NetRexx */
options replace format comments java crossref symbols nobinary
numeric digits 2000
runSample(arg)
return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Euclid's algorithm - iterative implementation
method gcdEucidI(a_, b_) public static
loop while b_ > 0
c_ = a_ // b_
a_ = b_
b_ = c_
end
return a_
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Euclid's algorithm - recursive implementation
method gcdEucidR(a_, b_) public static
if b_ \= 0 then a_ = gcdEucidR(b_, a_ // b_)
return a_
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method runSample(arg) private static
-- pairs of numbers, each number in the pair separated by a colon, each pair separated by a comma
parse arg tests
if tests = '' then
tests = '0:0, 6:4, 7:21, 12:36, 33:77, 41:47, 99:51, 100:5, 7:23, 1989:867, 12345:9876, 40902:24140, 49865:69811, 137438691328:2305843008139952128'
-- most of what follows is for formatting
xiterate = 0
xrecurse = 0
ll_ = 0
lr_ = 0
lgi = 0
lgr = 0
loop i_ = 1 until tests = ''
xiterate[0] = i_
xrecurse[0] = i_
parse tests pair ',' tests
parse pair l_ ':' r_ .
-- get the GCDs
gcdi = gcdEucidI(l_, r_)
gcdr = gcdEucidR(l_, r_)
xiterate[i_] = l_ r_ gcdi
xrecurse[i_] = l_ r_ gcdr
ll_ = ll_.max(l_.strip.length)
lr_ = lr_.max(r_.strip.length)
lgi = lgi.max(gcdi.strip.length)
lgr = lgr.max(gcdr.strip.length)
end i_
-- save formatter sizes in stems
xiterate[-1] = ll_ lr_ lgi
xrecurse[-1] = ll_ lr_ lgr
-- present results
showResults(xiterate, 'Euclid''s algorithm - iterative')
showResults(xrecurse, 'Euclid''s algorithm - recursive')
say
if verifyResults(xiterate, xrecurse) then
say 'Success: Results of iterative and recursive methods match'
else
say 'Error: Results of iterative and recursive methods do not match'
say
return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method showResults(stem, title) public static
say
say title
parse stem[-1] ll lr lg
loop v_ = 1 to stem[0]
parse stem[v_] lv rv gcd .
say lv.right(ll)',' rv.right(lr) ':' gcd.right(lg)
end v_
return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method verifyResults(stem1, stem2) public static returns boolean
if stem1[0] \= stem2[0] then signal BadArgumentException
T = (1 == 1)
F = \T
verified = T
loop i_ = 1 to stem1[0]
if stem1[i_] \= stem2[i_] then do
verified = F
leave i_
end
end i_
return verified
Output:
Euclid's algorithm - iterative
0, 0 : 0
6, 4 : 2
7, 21 : 7
12, 36 : 12
33, 77 : 11
41, 47 : 1
99, 51 : 3
100, 5 : 5
7, 23 : 1
1989, 867 : 51
12345, 9876 : 2469
40902, 24140 : 34
49865, 69811 : 9973
137438691328, 2305843008139952128 : 262144
Euclid's algorithm - recursive
0, 0 : 0
6, 4 : 2
7, 21 : 7
12, 36 : 12
33, 77 : 11
41, 47 : 1
99, 51 : 3
100, 5 : 5
7, 23 : 1
1989, 867 : 51
12345, 9876 : 2469
40902, 24140 : 34
49865, 69811 : 9973
137438691328, 2305843008139952128 : 262144
Success: Results of iterative and recursive methods match
NewLISP
(gcd 12 36)
→ 12
Nial
Nial provides gcd in the standard lib.
|loaddefs 'niallib/gcd.ndf'
|gcd 6 4
=2
defining it for arrays
# red is the reduction operator for a sorted list
# one is termination condition
red is cull filter (0 unequal) link [mod [rest, first] , first]
one is or [= [1 first, tally], > [2 first, first]]
gcd is fork [one, first, gcd red] sort <=
Using it
|gcd 9 6 3
=3
Nim
Ported from Pascal example
Recursive Euclid algorithm
proc gcd_recursive(u, v: int64): int64 = if u %% v != 0: result = gcd_recursive(v, u %% v) else: result = v
Iterative Euclid algorithm
proc gcd_iterative(u1, v1: int64): int64 = var t: int64 = 0 var u = u1 var v = v1 while v != 0: t = u u = v v = t %% v result = abs(u)
Iterative binary algorithm
proc gcd_binary(u1, v1: int64): int64 = var t, k: int64 var u = u1 var v = v1 u = abs(u) v = abs(v) if u < v: t = u u = v v = t if v == 0: result = u else: k = 1 while (u %% 2 == 0) and (v %% 2 == 0): u = u shl 1 v = v shl 1 k = k shr 1 if (u %% 2) == 0: t = u else: t = -v while t != 0: while (t %% 2) == 0: t = t div 2 if t > 0: u = t else: v = -t t = u - v result = u * k echo ("GCD(", 49865, ", ", 69811, "): ", gcd_iterative(49865, 69811), " (iterative)") echo ("GCD(", 49865, ", ", 69811, "): ", gcd_recursive(49865, 69811), " (recursive)") echo ("GCD(", 49865, ", ", 69811, "): ", gcd_binary (49865, 69811), " (binary)")
Output:
GCD(49865, 69811): 9973 (iterative)
GCD(49865, 69811): 9973 (recursive)
GCD(49865, 69811): 9973 (binary)
Oberon-2
Works with oo2c version 2
MODULE GCD;
(* Greatest Common Divisor *)
IMPORT
Out;
PROCEDURE Gcd(a,b: LONGINT):LONGINT;
VAR
r: LONGINT;
BEGIN
LOOP
r := a MOD b;
IF r = 0 THEN RETURN b END;
a := b;b := r
END
END Gcd;
BEGIN
Out.String("GCD of 12 and 8 : ");Out.LongInt(Gcd(12,8),4);Out.Ln;
Out.String("GCD of 100 and 5 : ");Out.LongInt(Gcd(100,5),4);Out.Ln;
Out.String("GCD of 7 and 23 : ");Out.LongInt(Gcd(7,23),4);Out.Ln;
Out.String("GCD of 24 and -112 : ");Out.LongInt(Gcd(12,8),4);Out.Ln;
Out.String("GCD of 40902 and 24140 : ");Out.LongInt(Gcd(40902,24140),4);Out.Ln
END GCD.
Output:
GCD of 12 and 8 : 4
GCD of 100 and 5 : 5
GCD of 7 and 23 : 1
GCD of 24 and -112 : 4
GCD of 40902 and 24140 : 34
Objeck
bundle Default {
class GDC {
function : Main(args : String[]), Nil {
for(x := 1; x < 36; x += 1;) {
IO.Console->GetInstance()->Print("GCD of ")->Print(36)->Print(" and ")->Print(x)->Print(" is ")->PrintLine(GDC(36, x));
};
}
function : native : GDC(a : Int, b : Int), Int {
t : Int;
if(a > b) {
t := b; b := a; a := t;
};
while (b <> 0) {
t := a % b; a := b; b := t;
};
return a;
}
}
}
OCaml
let rec gcd a b = if a = 0 then b else if b = 0 then a else if a > b then gcd b (a mod b) else gcd a (b mod a)
A little more idiomatic version:
let rec gcd1 a b = match (a mod b) with 0 -> b | r -> gcd1 b r
Built-in
#load "nums.cma";; open Big_int;; let gcd a b = int_of_big_int (gcd_big_int (big_int_of_int a) (big_int_of_int b))
Octave
r = gcd(a, b)
Oforth
gcd is already defined into Integer class :
128 96 gcd
Source of this method is (see Integer.of file) :
Integer method: gcd self while ( dup ) [ tuck mod ] drop ;
Ol
(print (gcd 1071 1029))
; ==> 21
Order
Translated from bc.
#include <order/interpreter.h> #define ORDER_PP_DEF_8gcd ORDER_PP_FN( \ 8fn(8U, 8V, \ 8if(8isnt_0(8V), 8gcd(8V, 8remainder(8U, 8V)), 8U))) // No support for negative numbers
Oz
declare
fun {UnsafeGCD A B}
if B == 0 then
A
else
{UnsafeGCD B A mod B}
end
end
fun {GCD A B}
if A == 0 andthen B == 0 then
raise undefined(gcd 0 0) end
else
{UnsafeGCD {Abs A} {Abs B}}
end
end
in
{Show {GCD 456 ~632}}
PARI/GP
gcd(a,b)
program GCF (INPUT, OUTPUT); var a,b,c:integer; begin writeln('Enter 1st number'); read(a); writeln('Enter 2nd number'); read(b); while (a*b<>0) do begin c:=a; a:=b mod a; b:=c; end; writeln('GCF :=', a+b ); end.
Pascal / Delphi / Free Pascal
Recursive Euclid algorithm
function gcd_recursive(u, v: longint): longint; begin if u mod v <> 0 then gcd_recursive := gcd_recursive(v, u mod v) else gcd_recursive := v; end;
Iterative Euclid algorithm
function gcd_iterative(u, v: longint): longint;
var
t: longint;
begin
while v <> 0 do
begin
t := u;
u := v;
v := t mod v;
end;
gcd_iterative := abs(u);
end;
Iterative binary algorithm
function gcd_binary(u, v: longint): longint; var t, k: longint; begin u := abs(u); v := abs(v); if u < v then begin t := u; u := v; v := t; end; if v = 0 then gcd_binary := u else begin k := 1; while (u mod 2 = 0) and (v mod 2 = 0) do begin u := u >> 1; v := v >> 1; k := k << 1; end; if u mod 2 = 0 then t := u else t := -v; while t <> 0 do begin while t mod 2 = 0 do t := t div 2; if t > 0 then u := t else v := -t; t := u - v; end; gcd_binary := u * k; end; end;
Demo program:
Program GreatestCommonDivisorDemo(output); begin writeln ('GCD(', 49865, ', ', 69811, '): ', gcd_iterative(49865, 69811), ' (iterative)'); writeln ('GCD(', 49865, ', ', 69811, '): ', gcd_recursive(49865, 69811), ' (recursive)'); writeln ('GCD(', 49865, ', ', 69811, '): ', gcd_binary (49865, 69811), ' (binary)'); end.
Output:
GCD(49865, 69811): 9973 (iterative)
GCD(49865, 69811): 9973 (recursive)
GCD(49865, 69811): 9973 (binary)
Perl
Iterative Euclid algorithm
sub gcd_iter($$) { my ($u, $v) = @_; while ($v) { ($u, $v) = ($v, $u % $v); } return abs($u); }
Recursive Euclid algorithm
sub gcd($$) { my ($u, $v) = @_; if ($v) { return gcd($v, $u % $v); } else { return abs($u); } }
Iterative binary algorithm
sub gcd_bin($$) { my ($u, $v) = @_; $u = abs($u); $v = abs($v); if ($u < $v) { ($u, $v) = ($v, $u); } if ($v == 0) { return $u; } my $k = 1; while ($u & 1 == 0 && $v & 1 == 0) { $u >>= 1; $v >>= 1; $k <<= 1; } my $t = ($u & 1) ? -$v : $u; while ($t) { while ($t & 1 == 0) { $t >>= 1; } if ($t > 0) { $u = $t; } else { $v = -$t; } $t = $u - $v; } return $u * $k; }
Modules
All three modules will take large integers as input, e.g. gcd("68095260063025322303723429387", "51306142182612010300800963053"). Other possibilities are Math::Cephes euclid, Math::GMPz gcd and gcd_ui.
# Fastest, takes multiple inputs use Math::Prime::Util "gcd"; $gcd = gcd(49865, 69811); # In CORE. Slowest, takes multiple inputs, result is a Math::BigInt unless converted use Math::BigInt; $gcd = Math::BigInt::bgcd(49865, 69811)->numify; # Result is a Math::Pari object unless converted use Math::Pari "gcd"; $gcd = gcd(49865, 69811)->pari2iv
Notes on performance
use Benchmark qw(cmpthese); use Math::BigInt; use Math::Pari; use Math::Prime::Util; my $u = 40902; my $v = 24140; cmpthese(-5, { 'gcd_rec' => sub { gcd($u, $v); }, 'gcd_iter' => sub { gcd_iter($u, $v); }, 'gcd_bin' => sub { gcd_bin($u, $v); }, 'gcd_bigint' => sub { Math::BigInt::bgcd($u,$v)->numify(); }, 'gcd_pari' => sub { Math::Pari::gcd($u,$v)->pari2iv(); }, 'gcd_mpu' => sub { Math::Prime::Util::gcd($u,$v); }, });
Output on 'Intel i3930k 4.2GHz' / Linux / Perl 5.20:
Rate gcd_bigint gcd_bin gcd_rec gcd_iter gcd_pari gcd_mpu
gcd_bigint 39939/s -- -83% -94% -95% -98% -99%
gcd_bin 234790/s 488% -- -62% -70% -88% -97%
gcd_rec 614750/s 1439% 162% -- -23% -68% -91%
gcd_iter 793422/s 1887% 238% 29% -- -58% -89%
gcd_pari 1896544/s 4649% 708% 209% 139% -- -73%
gcd_mpu 7114798/s 17714% 2930% 1057% 797% 275% --
Perl 6
Iterative
sub gcd (Int $a is copy, Int $b is copy) {
$a & $b == 0 and fail;
($a, $b) = ($b, $a % $b) while $b;
return abs $a;
}
Recursive
multi gcd (0, 0) { fail }
multi gcd (Int $a, 0) { abs $a }
multi gcd (Int $a, Int $b) { gcd $b, $a % $b }
Concise
my &gcd = { ($^a.abs, $^b.abs, * % * ... 0)[*-2] }
Built-in infix
my $gcd = $a gcd $b;
Because it's an infix, you can use it with various meta-operators:
[gcd] @list; # reduce with gcd
@alist Zgcd @blist; # lazy zip with gcd
@alist Xgcd @blist; # lazy cross with gcd
@alist »gcd« @blist; # parallel gcd
Phix
result is always positive, except for gcd(0,0) which is 0
atom parameters allow greater precision, but any fractional parts are immediately and deliberately discarded.
Actually, it is an autoinclude, reproduced below. The first parameter can be a sequence, in which case the second parameter (if provided) is ignored.
function gcd(object u, atom v=0)
atom t
if sequence(u) then
v = u[1] -- (for the typecheck)
t = floor(abs(v))
for i=2 to length(u) do
v = u[i] -- (for the typecheck)
t = gcd(t,v)
end for
return t
end if
u = floor(abs(u))
v = floor(abs(v))
while v do
t = u
u = v
v = remainder(t, v)
end while
return u
end function
Sample results:
gcd(0,0) -- 0
gcd(24,-112) -- 8
gcd(0, 10) -- 10
gcd(10, 0) -- 10
gcd(-10, 0) -- 10
gcd(0, -10) -- 10
gcd(9, 6) -- 3
gcd(6, 9) -- 3
gcd(-6, 9) -- 3
gcd(9, -6) -- 3
gcd(6, -9) -- 3
gcd(-9, 6) -- 3
gcd(40902, 24140) -- 34
gcd(70000000000000000000,
60000000000000000000000)
-- 10000000000000000000
gcd({57,0,-45,-18,90,447}) -- 3
PicoLisp
(de gcd (A B)
(until (=0 B)
(let M (% A B)
(setq A B B M) ) )
(abs A) )
PHP
Iterative
function gcdIter($n, $m) {
while(true) {
if($n == $m) {
return $m;
}
if($n > $m) {
$n -= $m;
} else {
$m -= $n;
}
}
}
Recursive
function gcdRec($n, $m)
{
if($m > 0)
return gcdRec($m, $n % $m);
else
return abs($n);
}
PL/I
GCD: procedure (a, b) returns (fixed binary (31)) recursive;
declare (a, b) fixed binary (31);
if b = 0 then return (a);
return (GCD (b, mod(a, b)) );
end GCD;
Pop11
Built-in gcd
gcd_n(15, 12, 2) =>
Note: the last argument gives the number of other arguments (in this case 2).
Iterative Euclid algorithm
define gcd(k, l) -> r;
lvars k , l, r = l;
abs(k) -> k;
abs(l) -> l;
if k < l then (k, l) -> (l, k) endif;
while l /= 0 do
(l, k rem l) -> (k, l)
endwhile;
k -> r;
enddefine;
PostScript
/gcd {
{
{0 gt} {dup rup mod} {pop exit} ifte
} loop
}.
With no external lib, recursive
/gcd {
dup 0 ne {
dup 3 1 roll mod gcd
} { pop } ifelse
} def
PowerShell
Recursive Euclid Algorithm
function Get-GCD ($x, $y) { if ($x -eq $y) { return $y } if ($x -gt $y) { $a = $x $b = $y } else { $a = $y $b = $x } while ($a % $b -ne 0) { $tmp = $a % $b $a = $b $b = $tmp } return $b }
or shorter (taken from Python implementation)
function Get-GCD ($x, $y) { if ($y -eq 0) { $x } else { Get-GCD $y ($x%$y) } }
Iterative Euclid Algorithm
Based on Python implementation
Function Get-GCD( $x, $y ) { while ($y -ne 0) { $x, $y = $y, ($x % $y) } [Math]::abs($x) }
Prolog
Recursive Euclid Algorithm
gcd(X, 0, X):- !.
gcd(0, X, X):- !.
gcd(X, Y, D):- X > Y, !, Z is X mod Y, gcd(Y, Z, D).
gcd(X, Y, D):- Z is Y mod X, gcd(X, Z, D).
Repeated Subtraction
gcd(X, 0, X):- !.
gcd(0, X, X):- !.
gcd(X, Y, D):- X =< Y, !, Z is Y - X, gcd(X, Z, D).
gcd(X, Y, D):- gcd(Y, X, D).
PureBasic
'''Iterative'''
Procedure GCD(x, y)
Protected r
While y <> 0
r = x % y
x = y
y = r
Wend
ProcedureReturn y
EndProcedure
'''Recursive'''
Procedure GCD(x, y)
Protected r
r = x % y
If (r > 0)
y = GCD(y, r)
EndIf
ProcedureReturn y
EndProcedure
Purity
data Iterate = f => FoldNat <const id, g => $g . $f>
data Sub = Iterate Pred
data IsZero = <const True, const False> . UnNat
data Eq = FoldNat
<
const IsZero,
eq => n => IfThenElse (IsZero $n)
False
($eq (Pred $n))
>
data step = gcd => n => m =>
IfThenElse (Eq $m $n)
(Pair $m $n)
(IfThenElse (Compare Leq $n $m)
($gcd (Sub $m $n) $m)
($gcd (Sub $n $m) $n))
data gcd = Iterate (gcd => uncurry (step (curry $gcd)))
Python
Built-in
Works with Python 2.6+
from fractions import gcd
Works with Python 3.7
(Note that fractions.gcd is now deprecated in Python 3)
from math import gcd
Iterative Euclid algorithm
def gcd_iter(u, v): while v: u, v = v, u % v return abs(u)
Recursive Euclid algorithm
Interpreter: Python 2.5
def gcd(u, v): return gcd(v, u % v) if v else abs(u)
Tests
>>> gcd(0,0)
0
>>> gcd(0, 10) == gcd(10, 0) == gcd(-10, 0) == gcd(0, -10) == 10
True
>>> gcd(9, 6) == gcd(6, 9) == gcd(-6, 9) == gcd(9, -6) == gcd(6, -9) == gcd(-9, 6) == 3
True
>>> gcd(8, 45) == gcd(45, 8) == gcd(-45, 8) == gcd(8, -45) == gcd(-8, 45) == gcd(45, -8) == 1
True
>>> gcd(40902, 24140) # check Knuth :)
34
Iterative binary algorithm
See [[The Art of Computer Programming]] by Knuth (Vol.2)
def gcd_bin(u, v): u, v = abs(u), abs(v) # u >= 0, v >= 0 if u < v: u, v = v, u # u >= v >= 0 if v == 0: return u # u >= v > 0 k = 1 while u & 1 == 0 and v & 1 == 0: # u, v - even u >>= 1; v >>= 1 k <<= 1 t = -v if u & 1 else u while t: while t & 1 == 0: t >>= 1 if t > 0: u = t else: v = -t t = u - v return u * k
Notes on performance
gcd(40902, 24140) takes about '''17''' µsec (Euclid, not built-in)
gcd_iter(40902, 24140) takes about '''11''' µsec
gcd_bin(40902, 24140) takes about '''41''' µsec
Qi
(define gcd
A 0 -> A
A B -> (gcd B (MOD A B)))
R
Recursive:
"%gcd%" <- function(u, v) { ifelse(u %% v != 0, v %gcd% (u%%v), v) }
Iterative:
"%gcd%" <- function(v, t) { while ( (c <- v%%t) != 0 ) { v <- t t <- c } t }
Output:
> print(50 %gcd% 75)
[1] 25
Racket
Racket provides a built-in gcd function. Here's a program that computes the gcd of 14 and 63:
#lang racket
(gcd 14 63)
Here's an explicit implementation. Note that since Racket is tail-calling, the memory behavior of this program is "loop-like", in the sense that this program will consume no more memory than a loop-based implementation.
#lang racket
;; given two nonnegative integers, produces their greatest
;; common divisor using Euclid's algorithm
(define (gcd a b)
(if (= b 0)
a
(gcd b (modulo a b))))
;; some test cases!
(module+ test
(require rackunit)
(check-equal? (gcd (* 2 3 3 7 7)
(* 3 3 7 11))
(* 3 3 7))
(check-equal? (gcd 0 14) 14)
(check-equal? (gcd 13 0) 13))
Rascal
Iterative Euclidean algorithm
public int gcd_iterative(int a, b){
if(a == 0) return b;
while(b != 0){
if(a > b) a -= b;
else b -= a;}
return a;
}
An example:
rascal>gcd_iterative(1989, 867)
int: 51
Recursive Euclidean algorithm
public int gcd_recursive(int a, b){
return (b == 0) ? a : gcd_recursive(b, a%b);
}
An example:
rascal>gcd_recursive(1989, 867)
int: 51
Raven
Recursive Euclidean algorithm
define gcd use $u, $v
$v 0 > if
$u $v % $v gcd
else
$u abs
24140 40902 gcd
Output:
34
REBOL
gcd: func [
{Returns the greatest common divisor of m and n.}
m [integer!]
n [integer!]
/local k
] [
; Euclid's algorithm
while [n > 0] [
k: m
m: n
n: k // m
]
m
]
Retro
This is from the math extensions library.
: gcd ( ab-n ) [ tuck mod dup ] while drop ;
REXX
version 1
The GCD subroutine can handle any number of arguments, it can also handle any number of integers within any
argument(s), making it easier to use when computing Frobenius numbers (also known as ''postage stamp'' or ''coin'' numbers).
/*REXX program calculates the GCD (Greatest Common Divisor) of any number of integers.*/
numeric digits 2000 /*handle up to 2k decimal dig integers.*/
call gcd 0 0 ; call gcd 55 0 ; call gcd 0 66
call gcd 7,21 ; call gcd 41,47 ; call gcd 99 , 51
call gcd 24, -8 ; call gcd -36, 9 ; call gcd -54, -6
call gcd 14 0 7 ; call gcd 14 7 0 ; call gcd 0 14 7
call gcd 15 10 20 30 55 ; call gcd 137438691328 2305843008139952128 /*◄──2 perfect#s*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
gcd: procedure; $=; do i=1 for arg(); $=$ arg(i); end /*arg list.*/
parse var $ x z .; if x=0 then x=z; x=abs(x) /* 0 case? */
do j=2 to words($); y=abs(word($,j)); if y=0 then iterate /*is zero? */
do until _==0; _=x//y; x=y; y=_; end /* ◄────────── the heavy lifting.*/
end /*j*/
say 'GCD (Greatest Common Divisor) of ' translate(space($),",",' ') " is " x
return x
Output:
GCD (Greatest Common Divisor) of 0,0 is 0
GCD (Greatest Common Divisor) of 55,0 is 55
GCD (Greatest Common Divisor) of 0,66 is 66
GCD (Greatest Common Divisor) of 7,21 is 7
GCD (Greatest Common Divisor) of 41,47 is 1
GCD (Greatest Common Divisor) of 99,51 is 3
GCD (Greatest Common Divisor) of 24,-8 is 8
GCD (Greatest Common Divisor) of -36,9 is 9
GCD (Greatest Common Divisor) of -54,-6 is 6
GCD (Greatest Common Divisor) of 14,0,7 is 7
GCD (Greatest Common Divisor) of 14,7,0 is 7
GCD (Greatest Common Divisor) of 0,14,7 is 7
GCD (Greatest Common Divisor) of 15,10,20,30,55 is 5
GCD (Greatest Common Divisor) of 137438691328,2305843008139952128 is 262144
version 2
Recursive function (as in PL/I):
/* REXX ***************************************************************
* using PL/I code extended to many arguments
* 17.08.2012 Walter Pachl
* 18.08.2012 gcd(0,0)=0
**********************************************************************/
numeric digits 300 /*handle up to 300 digit numbers.*/
Call test 7,21 ,'7 '
Call test 4,7 ,'1 '
Call test 24,-8 ,'8'
Call test 55,0 ,'55'
Call test 99,15 ,'3 '
Call test 15,10,20,30,55,'5'
Call test 496,8128 ,'16'
Call test 496,8128 ,'8' /* test wrong expectation */
Call test 0,0 ,'0' /* by definition */
Exit
test:
/**********************************************************************
* Test the gcd function
**********************************************************************/
n=arg() /* Number of arguments */
gcde=arg(n) /* Expected result */
gcdx=gcd(arg(1),arg(2)) /* gcd of the first 2 numbers */
Do i=2 To n-2 /* proceed with all the others */
If arg(i+1)<>0 Then
gcdx=gcd(gcdx,arg(i+1))
End
If gcdx=arg(arg()) Then /* result is as expected */
tag='as expected'
Else /* result is not correct */
Tag='*** wrong. expected:' gcde
numbers=arg(1) /* build string to show the input*/
Do i=2 To n-1
numbers=numbers 'and' arg(i)
End
say left('the GCD of' numbers 'is',45) right(gcdx,3) tag
Return
GCD: procedure
/**********************************************************************
* Recursive procedure as shown in PL/I
**********************************************************************/
Parse Arg a,b
if b = 0 then return abs(a)
return GCD(b,a//b)
Output:
the GCD of 7 and 21 is 7 as expected
the GCD of 4 and 7 is 1 as expected
the GCD of 24 and -8 is 8 as expected
the GCD of 55 and 0 is 55 as expected
the GCD of 99 and 15 is 3 as expected
the GCD of 15 and 10 and 20 and 30 and 55 is 5 as expected
the GCD of 496 and 8128 is 16 as expected
the GCD of 496 and 8128 is 16 *** wrong. expected: 8
the GCD of 0 and 0 is 0 as expected
version 3
Translated from REXX}} using different argument handlin.
Use as gcd(a,b,c,---)
Considerably faster than version 1 (and version 2)
See http://rosettacode.org/wiki/Least_common_multiple#REXX for reasoning.
gcd: procedure
x=abs(arg(1))
do j=2 to arg()
y=abs(arg(j))
If y<>0 Then Do
do until z==0
z=x//y
x=y
y=z
end
end
end
return x
Ring
see gcd (24, 32)
func gcd gcd, b
while b
c = gcd
gcd = b
b = c % b
end
return gcd
Ruby
That is already available as the gcd method of integers:
40902.gcd(24140) # => 34
Here's an implementation:
def gcd(u, v) u, v = u.abs, v.abs while v > 0 u, v = v, u % v end u end
Run BASIC
print abs(gcd(-220,160))
function gcd(gcd,b)
while b
c = gcd
gcd = b
b = c mod b
wend
end function
Rust
num crate
extern crate num; use num::integer::gcd;
Iterative Euclid algorithm
fn gcd(mut m: i32, mut n: i32) -> i32 { while m != 0 { let old_m = m; m = n % m; n = old_m; } n.abs() }
Recursive Euclid algorithm
fn gcd(m: i32, n: i32) -> i32 { if m == 0 { n.abs() } else { gcd(n % m, m) } }
Stein's Algorithm
Stein's algorithm is very much like Euclid's except that it uses bitwise operators (and consequently slightly more performant) and the integers must be unsigned. The following is a recursive implementation that leverages Rust's pattern matching.
use std::cmp::{min, max}; fn gcd(a: usize, b: usize) -> usize { match ((a, b), (a & 1, b & 1)) { ((x, y), _) if x == y => y, ((0, x), _) | ((x, 0), _) => x, ((x, y), (0, 1)) | ((y, x), (1, 0)) => gcd(x >> 1, y), ((x, y), (0, 0)) => gcd(x >> 1, y >> 1) << 1, ((x, y), (1, 1)) => { let (x, y) = (min(x, y), max(x, y)); gcd((y - x) >> 1, x) } _ => unreachable!(), } }
Tests
println!("{}",gcd(399,-3999)); println!("{}",gcd(0,3999)); println!("{}",gcd(13*13,13*29)); 3 3999 13
Sather
Translated from bc.
class MATH is
gcd_iter(u, v:INT):INT is
loop while!( v.bool );
t ::= u; u := v; v := t % v;
end;
return u.abs;
end;
gcd(u, v:INT):INT is
if v.bool then return gcd(v, u%v); end;
return u.abs;
end;
private swap(inout a, inout b:INT) is
t ::= a;
a := b;
b := t;
end;
gcd_bin(u, v:INT):INT is
t:INT;
u := u.abs; v := v.abs;
if u < v then swap(inout u, inout v); end;
if v = 0 then return u; end;
k ::= 1;
loop while!( u.is_even and v.is_even );
u := u / 2; v := v / 2;
k := k * 2;
end;
if u.is_even then
t := -v;
else
t := u;
end;
loop while!( t.bool );
loop while!( t.is_even );
t := t / 2;
end;
if t > 0 then
u := t;
else
v := -t;
end;
t := u - v;
end;
return u * k;
end;
end;
class MAIN is
main is
a ::= 40902;
b ::= 24140;
#OUT + MATH::gcd_iter(a, b) + "\n";
#OUT + MATH::gcd(a, b) + "\n";
#OUT + MATH::gcd_bin(a, b) + "\n";
-- built in
#OUT + a.gcd(b) + "\n";
end;
end;
Sass/SCSS
Iterative Euclid's Algorithm
@function gcd($a,$b) {
@while $b > 0 {
$c: $a % $b;
$a: $b;
$b: $c;
}
@return $a;
}
Scala
def gcd(a: Int, b: Int): Int = if (b == 0) a.abs else gcd(b, a % b)
Using pattern matching
@tailrec def gcd(a: Int, b: Int): Int = { b match { case 0 => a case _ => gcd(b, (a % b)) } }
Scheme
(define (gcd a b)
(if (= b 0)
a
(gcd b (modulo a b))))
or using the standard function included with Scheme (takes any number of arguments):
(gcd a b)
Sed
#! /bin/sed -nf
# gcd.sed Copyright (c) 2010 by Paweł Zuzelski <[email protected]>
# dc.sed Copyright (c) 1995 - 1997 by Greg Ubben <[email protected]>
# usage:
#
# echo N M | ./gcd.sed
#
# Computes the greatest common divisor of N and M integers using euclidean
# algorithm.
s/^/|P|K0|I10|O10|?~/
s/$/ [lalb%sclbsalcsblb0<F]sF sasblFxlap/
:next
s/|?./|?/
s/|?#[ -}]*/|?/
/|?!*[lLsS;:<>=]\{0,1\}$/N
/|?!*[-+*/%^<>=]/b binop
/^|.*|?[dpPfQXZvxkiosStT;:]/b binop
/|?[_0-9A-F.]/b number
/|?\[/b string
/|?l/b load
/|?L/b Load
/|?[sS]/b save
/|?c/ s/[^|]*//
/|?d/ s/[^~]*~/&&/
/|?f/ s//&[pSbz0<aLb]dSaxsaLa/
/|?x/ s/\([^~]*~\)\(.*|?x\)~*/\2\1/
/|?[KIO]/ s/.*|\([KIO]\)\([^|]*\).*|?\1/\2~&/
/|?T/ s/\.*0*~/~/
# a slow, non-stackable array implementation in dc, just for completeness
# A fast, stackable, associative array implementation could be done in sed
# (format: {key}value{key}value...), but would be longer, like load & save.
/|?;/ s/|?;\([^{}]\)/|?~[s}s{L{s}q]S}[S}l\1L}1-d0>}s\1L\1l{xS\1]dS{xL}/
/|?:/ s/|?:\([^{}]\)/|?~[s}L{s}L{s}L}s\1q]S}S}S{[L}1-d0>}S}l\1s\1L\1l{xS\1]dS{x/
/|?[ ~ cdfxKIOT]/b next
/|?\n/b next
/|?[pP]/b print
/|?k/ s/^\([0-9]\{1,3\}\)\([.~].*|K\)[^|]*/\2\1/
/|?i/ s/^\(-\{0,1\}[0-9]*\.\{0,1\}[0-9]\{1,\}\)\(~.*|I\)[^|]*/\2\1/
/|?o/ s/^\(-\{0,1\}[1-9][0-9]*\.\{0,1\}[0-9]*\)\(~.*|O\)[^|]*/\2\1/
/|?[kio]/b pop
/|?t/b trunc
/|??/b input
/|?Q/b break
/|?q/b quit
h
/|?[XZz]/b count
/|?v/b sqrt
s/.*|?\([^Y]\).*/\1 is unimplemented/
s/\n/\\n/g
l
g
b next
:print
/^-\{0,1\}[0-9]*\.\{0,1\}[0-9]\{1,\}~.*|?p/!b Print
/|O10|/b Print
# Print a number in a non-decimal output base. Uses registers a,b,c,d.
# Handles fractional output bases (O<-1 or O>=1), unlike other dc's.
# Converts the fraction correctly on negative output bases, unlike
# UNIX dc. Also scales the fraction more accurately than UNIX dc.
#
s,|?p,&KSa0kd[[-]Psa0la-]Sad0>a[0P]sad0=a[A*2+]saOtd0>a1-ZSd[[[[ ]P]sclb1\
!=cSbLdlbtZ[[[-]P0lb-sb]sclb0>c1+]sclb0!<c[0P1+dld>c]scdld>cscSdLbP]q]Sb\
[t[1P1-d0<c]scd0<c]ScO_1>bO1!<cO[16]<bOX0<b[[q]sc[dSbdA>c[A]sbdA=c[B]sbd\
B=c[C]sbdC=c[D]sbdD=c[E]sbdE=c[F]sb]xscLbP]~Sd[dtdZOZ+k1O/Tdsb[.5]*[.1]O\
X^*dZkdXK-1+ktsc0kdSb-[Lbdlb*lc+tdSbO*-lb0!=aldx]dsaxLbsb]sad1!>a[[.]POX\
+sb1[SbO*dtdldx-LbO*dZlb!<a]dsax]sadXd0<asbsasaLasbLbscLcsdLdsdLdLak[]pP,
b next
:Print
/|?p/s/[^~]*/&\
~&/
s/\(.*|P\)\([^|]*\)/\
\2\1/
s/\([^~]*\)\n\([^~]*\)\(.*|P\)/\1\3\2/
h
s/~.*//
/./{ s/.//; p; }
# Just s/.//p would work if we knew we were running under the -n option.
# Using l vs p would kind of do \ continuations, but would break strings.
g
:pop
s/[^~]*~//
b next
:load
s/\(.*|?.\)\(.\)/\20~\1/
s/^\(.\)0\(.*|r\1\([^~|]*\)~\)/\1\3\2/
s/.//
b next
:Load
s/\(.*|?.\)\(.\)/\2\1/
s/^\(.\)\(.*|r\1\)\([^~|]*~\)/|\3\2/
/^|/!i\
register empty
s/.//
b next
:save
s/\(.*|?.\)\(.\)/\2\1/
/^\(.\).*|r\1/ !s/\(.\).*|/&r\1|/
/|?S/ s/\(.\).*|r\1/&~/
s/\(.\)\([^~]*~\)\(.*|r\1\)[^~|]*~\{0,1\}/\3\2/
b next
:quit
t quit
s/|?[^~]*~[^~]*~/|?q/
t next
# Really should be using the -n option to avoid printing a final newline.
s/.*|P\([^|]*\).*/\1/
q
:break
s/[0-9]*/&;987654321009;/
:break1
s/^\([^;]*\)\([1-9]\)\(0*\)\([^1]*\2\(.\)[^;]*\3\(9*\).*|?.\)[^~]*~/\1\5\6\4/
t break1
b pop
:input
N
s/|??\(.*\)\(\n.*\)/|?\2~\1/
b next
:count
/|?Z/ s/~.*//
/^-\{0,1\}[0-9]*\.\{0,1\}[0-9]\{1,\}$/ s/[-.0]*\([^.]*\)\.*/\1/
/|?X/ s/-*[0-9A-F]*\.*\([0-9A-F]*\).*/\1/
s/|.*//
/~/ s/[^~]//g
s/./a/g
:count1
s/a\{10\}/b/g
s/b*a*/&a9876543210;/
s/a.\{9\}\(.\).*;/\1/
y/b/a/
/a/b count1
G
/|?z/ s/\n/&~/
s/\n[^~]*//
b next
:trunc
# for efficiency, doesn't pad with 0s, so 10k 2 5/ returns just .40
# The X* here and in a couple other places works around a SunOS 4.x sed bug.
s/\([^.~]*\.*\)\(.*|K\([^|]*\)\)/\3;9876543210009909:\1,\2/
:trunc1
s/^\([^;]*\)\([1-9]\)\(0*\)\([^1]*\2\(.\)[^:]*X*\3\(9*\)[^,]*\),\([0-9]\)/\1\5\6\4\7,/
t trunc1
s/[^:]*:\([^,]*\)[^~]*/\1/
b normal
:number
s/\(.*|?\)\(_\{0,1\}[0-9A-F]*\.\{0,1\}[0-9A-F]*\)/\2~\1~/
s/^_/-/
/^[^A-F~]*~.*|I10|/b normal
/^[-0.]*~/b normal
s:\([^.~]*\)\.*\([^~]*\):[Ilb^lbk/,\1\2~0A1B2C3D4E5F1=11223344556677889900;.\2:
:digit
s/^\([^,]*\),\(-*\)\([0-F]\)\([^;]*\(.\)\3[^1;]*\(1*\)\)/I*+\1\2\6\5~,\2\4/
t digit
s:...\([^/]*.\)\([^,]*\)[^.]*\(.*|?.\):\2\3KSb[99]k\1]SaSaXSbLalb0<aLakLbktLbk:
b next
:string
/|?[^]]*$/N
s/\(|?[^]]*\)\[\([^]]*\)]/\1|{\2|}/
/|?\[/b string
s/\(.*|?\)|{\(.*\)|}/\2~\1[/
s/|{/[/g
s/|}/]/g
b next
:binop
/^[^~|]*~[^|]/ !i\
stack empty
//!b next
/^-\{0,1\}[0-9]*\.\{0,1\}[0-9]\{1,\}~/ !s/[^~]*\(.*|?!*[^!=<>]\)/0\1/
/^[^~]*~-\{0,1\}[0-9]*\.\{0,1\}[0-9]\{1,\}~/ !s/~[^~]*\(.*|?!*[^!=<>]\)/~0\1/
h
/|?\*/b mul
/|?\//b div
/|?%/b rem
/|?^/b exp
/|?[+-]/ s/^\(-*\)\([^~]*~\)\(-*\)\([^~]*~\).*|?\(-\{0,1\}\).*/\2\4s\3o\1\3\5/
s/\([^.~]*\)\([^~]*~[^.~]*\)\(.*\)/<\1,\2,\3|=-~.0,123456789<></
/^<\([^,]*,[^~]*\)\.*0*~\1\.*0*~/ s/</=/
:cmp1
s/^\(<[^,]*\)\([0-9]\),\([^,]*\)\([0-9]\),/\1,\2\3,\4/
t cmp1
/^<\([^~]*\)\([^~]\)[^~]*~\1\(.\).*|=.*\3.*\2/ s/</>/
/|?/{
s/^\([<>]\)\(-[^~]*~-.*\1\)\(.\)/\3\2/
s/^\(.\)\(.*|?!*\)\1/\2!\1/
s/|?![^!]\(.\)/&l\1x/
s/[^~]*~[^~]*~\(.*|?\)!*.\(.*\)|=.*/\1\2/
b next
}
s/\(-*\)\1|=.*/;9876543210;9876543210/
/o-/ s/;9876543210/;0123456789/
s/^>\([^~]*~\)\([^~]*~\)s\(-*\)\(-*o\3\(-*\)\)/>\2\1s\5\4/
s/,\([0-9]*\)\.*\([^,]*\),\([0-9]*\)\.*\([0-9]*\)/\1,\2\3.,\4;0/
:right1
s/,\([0-9]\)\([^,]*\),;*\([0-9]\)\([0-9]*\);*0*/\1,\2\3,\4;0/
t right1
s/.\([^,]*\),~\(.*\);0~s\(-*\)o-*/\1~\30\2~/
:addsub1
s/\(.\{0,1\}\)\(~[^,]*\)\([0-9]\)\(\.*\),\([^;]*\)\(;\([^;]*\(\3[^;]*\)\).*X*\1\(.*\)\)/\2,\4\5\9\8\7\6/
s/,\([^~]*~\).\{10\}\(.\)[^;]\{0,9\}\([^;]\{0,1\}\)[^;]*/,\2\1\3/
# could be done in one s/// if we could have >9 back-refs...
/^~.*~;/!b addsub1
:endbin
s/.\([^,]*\),\([0-9.]*\).*/\1\2/
G
s/\n[^~]*~[^~]*//
:normal
s/^\(-*\)0*\([0-9.]*[0-9]\)[^~]*/\1\2/
s/^[^1-9~]*~/0~/
b next
:mul
s/\(-*\)\([0-9]*\)\.*\([0-9]*\)~\(-*\)\([0-9]*\)\.*\([0-9]*\).*|K\([^|]*\).*/\1\4\2\5.!\3\6,|\2<\3~\5>\6:\7;9876543210009909/
:mul1
s/![0-9]\([^<]*\)<\([0-9]\{0,1\}\)\([^>]*\)>\([0-9]\{0,1\}\)/0!\1\2<\3\4>/
/![0-9]/ s/\(:[^;]*\)\([1-9]\)\(0*\)\([^0]*\2\(.\).*X*\3\(9*\)\)/\1\5\6\4/
/<~[^>]*>:0*;/!t mul1
s/\(-*\)\1\([^>]*\).*/;\2^>:9876543210aaaaaaaaa/
:mul2
s/\([0-9]~*\)^/^\1/
s/<\([0-9]*\)\(.*[~^]\)\([0-9]*\)>/\1<\2>\3/
:mul3
s/>\([0-9]\)\(.*\1.\{9\}\(a*\)\)/\1>\2;9\38\37\36\35\34\33\32\31\30/
s/\(;[^<]*\)\([0-9]\)<\([^;]*\).*\2[0-9]*\(.*\)/\4\1<\2\3/
s/a[0-9]/a/g
s/a\{10\}/b/g
s/b\{10\}/c/g
/|0*[1-9][^>]*>0*[1-9]/b mul3
s/;/a9876543210;/
s/a.\{9\}\(.\)[^;]*\([^,]*\)[0-9]\([.!]*\),/\2,\1\3/
y/cb/ba/
/|<^/!b mul2
b endbin
:div
# CDDET
/^[-.0]*[1-9]/ !i\
divide by 0
//!b pop
s/\(-*\)\([0-9]*\)\.*\([^~]*~-*\)\([0-9]*\)\.*\([^~]*\)/\2.\3\1;0\4.\5;0/
:div1
s/^\.0\([^.]*\)\.;*\([0-9]\)\([0-9]*\);*0*/.\1\2.\3;0/
s/^\([^.]*\)\([0-9]\)\.\([^;]*;\)0*\([0-9]*\)\([0-9]\)\./\1.\2\30\4.\5/
t div1
s/~\(-*\)\1\(-*\);0*\([^;]*[0-9]\)[^~]*/~123456789743222111~\2\3/
s/\(.\(.\)[^~]*\)[^9]*\2.\{8\}\(.\)[^~]*/\3~\1/
s,|?.,&SaSadSaKdlaZ+LaX-1+[sb1]Sbd1>bkLatsbLa[dSa2lbla*-*dLa!=a]dSaxsakLasbLb*t,
b next
:rem
s,|?%,&Sadla/LaKSa[999]k*Lak-,
b next
:exp
# This decimal method is just a little faster than the binary method done
# totally in dc: 1LaKLb [kdSb*LbK]Sb [[.5]*d0ktdSa<bkd*KLad1<a]Sa d1<a kk*
/^[^~]*\./i\
fraction in exponent ignored
s,[^-0-9].*,;9d**dd*8*d*d7dd**d*6d**d5d*d*4*d3d*2lbd**1lb*0,
:exp1
s/\([0-9]\);\(.*\1\([d*]*\)[^l]*\([^*]*\)\(\**\)\)/;dd*d**d*\4\3\5\2/
t exp1
G
s,-*.\{9\}\([^9]*\)[^0]*0.\(.*|?.\),\2~saSaKdsaLb0kLbkK*+k1\1LaktsbkLax,
s,|?.,&SadSbdXSaZla-SbKLaLadSb[0Lb-d1lb-*d+K+0kkSb[1Lb/]q]Sa0>a[dk]sadK<a[Lb],
b next
:sqrt
# first square root using sed: 8k2v at 1:30am Dec 17, 1996
/^-/i\
square root of negative number
/^[-0]/b next
s/~.*//
/^\./ s/0\([0-9]\)/\1/g
/^\./ !s/[0-9][0-9]/7/g
G
s/\n/~/
s,|?.,&K1+k KSbSb[dk]SadXdK<asadlb/lb+[.5]*[sbdlb/lb+[.5]*dlb>a]dsaxsasaLbsaLatLbk K1-kt,
b next
# END OF GSU dc.sed
Seed7
const func integer: gcd (in var integer: a, in var integer: b) is func
result
var integer: gcd is 0;
local
var integer: help is 0;
begin
while a <> 0 do
help := b rem a;
b := a;
a := help;
end while;
gcd := b;
end func;
Original source: http://seed7.sourceforge.net/algorith/math.htm#gcd
SequenceL
Tail Recursive Greatest Common Denominator using Euclidian Algorithm
gcd(a, b) :=
a when b = 0
else
gcd(b, a mod b);
SETL
a := 33; b := 77;
print(" the gcd of",a," and ",b," is ",gcd(a,b));
c := 49865; d := 69811;
print(" the gcd of",c," and ",d," is ",gcd(c,d));
proc gcd (u, v);
return if v = 0 then abs u else gcd (v, u mod v) end;
end;
Output:
the gcd of 33 and 77 is 11
the gcd of 49865 and 69811 is 9973
Sidef
Built-in
var arr = [100, 1_000, 10_000, 20]; say Math.gcd(arr...);
Recursive Euclid algorithm
func gcd(a, b) { b.is_zero ? a.abs : gcd(b, a % b); }
Simula
For a recursive variant, see [[Sum multiples of 3 and 5#Simula|Sum multiples of 3 and 5]].
BEGIN
INTEGER PROCEDURE GCD(a, b); INTEGER a, b;
BEGIN
IF a = 0 THEN a := b
ELSE
WHILE 0 < b DO BEGIN INTEGER i;
i := MOD(a, b); a := b; b := i;
END;
GCD := a
END;
INTEGER a, b;
!outint(SYSOUT.IMAGE.MAIN.LENGTH, 0);!OUTIMAGE;!OUTIMAGE;
!SYSOUT.IMAGE :- BLANKS(132); ! this may or may not work;
FOR b := 1 STEP 5 UNTIL 37 DO BEGIN
FOR a := 0 STEP 2 UNTIL 21 DO BEGIN
OUTTEXT(" ("); OUTINT(a, 0);
OUTCHAR(','); OUTINT(b, 2);
OUTCHAR(')'); OUTINT(GCD(a, b), 3);
END;
OUTIMAGE
END
END
Output:
(0, 1) 1 (2, 1) 1 (4, 1) 1 (6, 1) 1 (8, 1) 1 (10, 1) 1 (12, 1) 1 (14, 1) 1 (16, 1) 1 (18, 1) 1 (20, 1) 1
(0, 6) 6 (2, 6) 2 (4, 6) 2 (6, 6) 6 (8, 6) 2 (10, 6) 2 (12, 6) 6 (14, 6) 2 (16, 6) 2 (18, 6) 6 (20, 6) 2
(0,11) 11 (2,11) 1 (4,11) 1 (6,11) 1 (8,11) 1 (10,11) 1 (12,11) 1 (14,11) 1 (16,11) 1 (18,11) 1 (20,11) 1
(0,16) 16 (2,16) 2 (4,16) 4 (6,16) 2 (8,16) 8 (10,16) 2 (12,16) 4 (14,16) 2 (16,16) 16 (18,16) 2 (20,16) 4
(0,21) 21 (2,21) 1 (4,21) 1 (6,21) 3 (8,21) 1 (10,21) 1 (12,21) 3 (14,21) 7 (16,21) 1 (18,21) 3 (20,21) 1
(0,26) 26 (2,26) 2 (4,26) 2 (6,26) 2 (8,26) 2 (10,26) 2 (12,26) 2 (14,26) 2 (16,26) 2 (18,26) 2 (20,26) 2
(0,31) 31 (2,31) 1 (4,31) 1 (6,31) 1 (8,31) 1 (10,31) 1 (12,31) 1 (14,31) 1 (16,31) 1 (18,31) 1 (20,31) 1
(0,36) 36 (2,36) 2 (4,36) 4 (6,36) 6 (8,36) 4 (10,36) 2 (12,36) 12 (14,36) 2 (16,36) 4 (18,36) 18 (20,36) 4
Slate
Slate's Integer type has gcd defined:
40902 gcd: 24140
Iterative Euclid algorithm
x@(Integer traits) gcd: y@(Integer traits)
"Euclid's algorithm for finding the greatest common divisor."
[| n m temp |
n: x.
m: y.
[n isZero] whileFalse: [temp: n. n: m \\ temp. m: temp].
m abs
].
Recursive Euclid algorithm
x@(Integer traits) gcd: y@(Integer traits)
[
y isZero
ifTrue: [x]
ifFalse: [y gcd: x \\ y]
].
Smalltalk
The Integer class has its gcd method.
(40902 gcd: 24140) displayNl
An reimplementation of the Iterative Euclid's algorithm would be:
|gcd_iter|
gcd_iter := [ :a :b |
|u v|
u := a. v := b.
[ v > 0 ]
whileTrue: [ |t|
t := u.
u := v.
v := t rem: v
].
u abs
].
(gcd_iter value: 40902 value: 24140) printNl.
SNOBOL4
define('gcd(i,j)') :(gcd_end)
gcd ?eq(i,0) :s(freturn)
?eq(j,0) :s(freturn)
loop gcd = remdr(i,j)
gcd = ?eq(gcd,0) j :s(return)
i = j
j = gcd :(loop)
gcd_end
output = gcd(1071,1029)
end
Sparkling
function factors(n) {
var f = {};
for var i = 2; n > 1; i++ {
while n % i == 0 {
n /= i;
f[i] = f[i] != nil ? f[i] + 1 : 1;
}
}
return f;
}
function GCD(n, k) {
let f1 = factors(n);
let f2 = factors(k);
let fs = map(f1, function(factor, multiplicity) {
let m = f2[factor];
return m == nil ? 0 : min(m, multiplicity);
});
let rfs = {};
foreach(fs, function(k, v) {
rfs[sizeof rfs] = pow(k, v);
});
return reduce(rfs, 1, function(x, y) { return x * y; });
}
function LCM(n, k) {
return n * k / GCD(n, k);
}
SQL
Demonstration of Oracle 12c WITH Clause Enhancements
drop table tbl; create table tbl ( u number, v number ); insert into tbl ( u, v ) values ( 20, 50 ); insert into tbl ( u, v ) values ( 21, 50 ); insert into tbl ( u, v ) values ( 21, 51 ); insert into tbl ( u, v ) values ( 22, 50 ); insert into tbl ( u, v ) values ( 22, 55 ); commit; with function gcd ( ui in number, vi in number ) return number is u number := ui; v number := vi; t number; begin while v > 0 loop t := u; u := v; v:= mod(t, v ); end loop; return abs(u); end gcd; select u, v, gcd ( u, v ) from tbl /
Output:
Table dropped.
Table created.
1 row created.
1 row created.
1 row created.
1 row created.
1 row created.
Commit complete.
U V GCD(U,V)
---------- ---------- ----------
20 50 10
21 50 1
21 51 3
22 50 2
22 55 11
Demonstration of SQL Server 2008
CREATE FUNCTION gcd ( @ui INT, @vi INT ) RETURNS INT AS BEGIN DECLARE @t INT DECLARE @u INT DECLARE @v INT SET @u = @ui SET @v = @vi WHILE @v > 0 BEGIN SET @t = @u; SET @u = @v; SET @v = @t % @v; END; RETURN abs( @u ); END GO CREATE TABLE tbl ( u INT, v INT ); INSERT INTO tbl ( u, v ) VALUES ( 20, 50 ); INSERT INTO tbl ( u, v ) VALUES ( 21, 50 ); INSERT INTO tbl ( u, v ) VALUES ( 21, 51 ); INSERT INTO tbl ( u, v ) VALUES ( 22, 50 ); INSERT INTO tbl ( u, v ) VALUES ( 22, 55 ); SELECT u, v, dbo.gcd ( u, v ) FROM tbl; DROP TABLE tbl; DROP FUNCTION gcd;
PostgreSQL function using a recursive common table expression
CREATE FUNCTION gcd(integer, integer) RETURNS integer LANGUAGE sql AS $function$ WITH RECURSIVE x (u, v) AS ( SELECT ABS($1), ABS($2) UNION SELECT v, u % v FROM x WHERE v > 0 ) SELECT min(u) FROM x; $function$
Output:
postgres> select gcd(40902, 24140);
gcd
-----
34
SELECT 1
Time: 0.012s
Stata
function gcd(a_,b_) {
a = abs(a_)
b = abs(b_)
while (b>0) {
a = mod(a,b)
swap(a,b)
}
return(a)
}
Swift
// Iterative func gcd(var a: Int, var b: Int) -> Int { a = abs(a); b = abs(b) if (b > a) { swap(&a, &b) } while (b > 0) { (a, b) = (b, a % b) } return a } // Recursive func gcdr (var a: Int, var b: Int) -> Int { a = abs(a); b = abs(b) if (b > a) { swap(&a, &b) } return gcd_rec(a,b) } private func gcd_rec(a: Int, b: Int) -> Int { return b == 0 ? a : gcd_rec(b, a % b) } for (a,b) in [(1,1), (100, -10), (10, -100), (-36, -17), (27, 18), (30, -42)] { println("Iterative: GCD of \(a) and \(b) is \(gcd(a, b))") println("Recursive: GCD of \(a) and \(b) is \(gcdr(a, b))") }
Output:
Iterative: GCD of 1 and 1 is 1
Recursive: GCD of 1 and 1 is 1
Iterative: GCD of 100 and -10 is 10
Recursive: GCD of 100 and -10 is 10
Iterative: GCD of 10 and -100 is 10
Recursive: GCD of 10 and -100 is 10
Iterative: GCD of -36 and -17 is 1
Recursive: GCD of -36 and -17 is 1
Iterative: GCD of 27 and 18 is 9
Recursive: GCD of 27 and 18 is 9
Iterative: GCD of 30 and -42 is 6
Recursive: GCD of 30 and -42 is 6
Tcl
Iterative Euclid algorithm
package require Tcl 8.5 namespace path {::tcl::mathop ::tcl::mathfunc} proc gcd_iter {p q} { while {$q != 0} { lassign [list $q [% $p $q]] p q } abs $p }
Recursive Euclid algorithm
proc gcd {p q} { if {$q == 0} { return $p } gcd $q [expr {$p % $q}] }
With Tcl 8.6, this can be optimized slightly to:
proc gcd {p q} { if {$q == 0} { return $p } tailcall gcd $q [expr {$p % $q}] }
(Tcl does not perform automatic tail-call optimization introduction because that makes any potential error traces less informative.)
Iterative binary algorithm
package require Tcl 8.5 namespace path {::tcl::mathop ::tcl::mathfunc} proc gcd_bin {p q} { if {$p == $q} {return [abs $p]} set p [abs $p] if {$q == 0} {return $p} set q [abs $q] if {$p < $q} {lassign [list $q $p] p q} set k 1 while {($p & 1) == 0 && ($q & 1) == 0} { set p [>> $p 1] set q [>> $q 1] set k [<< $k 1] } set t [expr {$p & 1 ? -$q : $p}] while {$t} { while {$t & 1 == 0} {set t [>> $t 1]} if {$t > 0} {set p $t} {set q [- $t]} set t [- $p $q] } return [* $p $k] }
Notes on performance
foreach proc {gcd_iter gcd gcd_bin} { puts [format "%-8s - %s" $proc [time {$proc $u $v} 100000]] }
Outputs:
gcd_iter - 4.46712 microseconds per iteration
gcd - 5.73969 microseconds per iteration
gcd_bin - 9.25613 microseconds per iteration
TI-83 BASIC, TI-89 BASIC
gcd(A,B)
The ) can be omitted in TI-83 basic
TSE SAL
INTEGER PROC FNMathGetGreatestCommonDivisorI( INTEGER x1I, INTEGER x2I )
//
IF ( x2I == 0 )
//
RETURN( x1I )
//
ENDIF
//
RETURN( FNMathGetGreatestCommonDivisorI( x2I, x1I MOD x2I ) )
//
END
PROC Main()
STRING s1[255] = "353"
STRING s2[255] = "46"
REPEAT
IF ( NOT ( Ask( " = ", s1, _EDIT_HISTORY_ ) ) AND ( Length( s1 ) > 0 ) ) RETURN() ENDIF
IF ( NOT ( Ask( " = ", s2, _EDIT_HISTORY_ ) ) AND ( Length( s2 ) > 0 ) ) RETURN() ENDIF
Warn( FNMathGetGreatestCommonDivisorI( Val( s1 ), Val( s2 ) ) ) // gives e.g. 1
UNTIL FALSE
END
TXR
$ txr -p '(gcd (expt 2 123) (expt 6 49))' 562949953421312
TypeScript
Iterative implementation
function gcd(a: number, b: number) { a = Math.abs(a); b = Math.abs(b); if (b > a) { let temp = a; a = b; b = temp; } while (true) { a %= b; if (a === 0) { return b; } b %= a; if (b === 0) { return a; } } }
Recursive:
function gcd_rec(a: number, b: number) { return b ? gcd_rec(b, a % b) : Math.abs(a); }
uBasic/4tH
Translated from BBC BASIC.
Print "GCD of 18 : 12 = "; FUNC(_GCD_Iterative_Euclid(18,12))
Print "GCD of 1071 : 1029 = "; FUNC(_GCD_Iterative_Euclid(1071,1029))
Print "GCD of 3528 : 3780 = "; FUNC(_GCD_Iterative_Euclid(3528,3780))
End
_GCD_Iterative_Euclid Param(2)
Local (1)
Do While b@
c@ = a@
a@ = b@
b@ = c@ % b@
Loop
Return (Abs(a@))
Output:
GCD of 18 : 12 = 6
GCD of 1071 : 1029 = 21
GCD of 3528 : 3780 = 252
0 OK, 0:205
UNIX Shell
Works with Bourne Shell
gcd() { # Calculate $1 % $2 until $2 becomes zero. until test 0 -eq "$2"; do # Parallel assignment: set -- 1 2 set -- "$2" "`expr "$1" % "$2"`" done # Echo absolute value of $1. test 0 -gt "$1" && set -- "`expr 0 - "$1"`" echo "$1" } gcd -47376 87843 # => 987
C Shell
alias gcd eval \''set gcd_args=( \!*:q ) \\
@ gcd_u=$gcd_args[2] \\
@ gcd_v=$gcd_args[3] \\
while ( $gcd_v != 0 ) \\
@ gcd_t = $gcd_u % $gcd_v \\
@ gcd_u = $gcd_v \\
@ gcd_v = $gcd_t \\
end \\
if ( $gcd_u < 0 ) @ gcd_u = - $gcd_u \\
@ $gcd_args[1]=$gcd_u \\
'\'
gcd result -47376 87843
echo $result
# => 987
Ursa
import "math"
out (gcd 40902 24140) endl console
Output:
34
Ursala
This doesn't need to be defined because it's a library function, but it can be defined like this based on a recursive implementation of Euclid's algorithm. This isn't the simplest possible solution because it includes a bit shifting optimization that happens when both operands are even.
#import nat
gcd = ~&B?\~&Y ~&alh^?\~&arh2faltPrXPRNfabt2RCQ @a ~&ar^?\~&al ^|R/~& ^/~&r remainder
test program:
#cast %nWnAL
test = ^(~&,gcd)* <(25,15),(36,16),(120,45),(30,100)>
Output:
<
(25,15): 5,
(36,16): 4,
(120,45): 15,
(30,100): 10>
V
Like joy
iterative
[gcd
[0 >] [dup rollup %]
while
pop
].
recursive
like python
[gcd
[zero?] [pop]
[swap [dup] dip swap %]
tailrec].
same with view: (swap [dup] dip swap % is replaced with a destructuring view)
[gcd
[zero?] [pop]
[[a b : [b a b %]] view i]
tailrec].
Running it:
|1071 1029 gcd
=21
VBA
Function gcd(u As Long, v As Long) As Long
Dim t As Long
Do While v
t = u
u = v
v = t Mod v
Loop
gcd = u
End Function
This function uses repeated subtractions. Simple but not very efficient.
Public Function GCD(a As Long, b As Long) As Long
While a <> b
If a > b Then a = a - b Else b = b - a
Wend
GCD = a
End Function
Output:
print GCD(1280, 240)
80
print GCD(3475689, 23566319)
7
a=123456789
b=234736437
print GCD((a),(b))
3
A note on the last example: using brackets forces a and b to be evaluated before GCD is called. Not doing this will cause a compile error, because a and b are not the same type as in the function declaration (they are Variant, not Long). Alternatively you can use the conversion function CLng as in print GCD(CLng(a),CLng(b))
VBScript
Function GCD(a,b)
Do
If a Mod b > 0 Then
c = a Mod b
a = b
b = c
Else
GCD = b
Exit Do
End If
Loop
End Function
WScript.Echo "The GCD of 48 and 18 is " & GCD(48,18) & "."
WScript.Echo "The GCD of 1280 and 240 is " & GCD(1280,240) & "."
WScript.Echo "The GCD of 1280 and 240 is " & GCD(3475689,23566319) & "."
WScript.Echo "The GCD of 1280 and 240 is " & GCD(123456789,234736437) & "."
Output:
The GCD of 48 and 18 is 6.
The GCD of 1280 and 240 is 80.
The GCD of 1280 and 240 is 7.
The GCD of 1280 and 240 is 3.
Verilog
module gcd
(
input reset_l,
input clk,
input [31:0] initial_u,
input [31:0] initial_v,
input load,
output reg [31:0] result,
output reg busy
);
reg [31:0] u, v;
always @(posedge clk or negedge reset_l)
if (!reset_l)
begin
busy <= 0;
u <= 0;
v <= 0;
end
else
begin
result <= u + v; // Result (one of them will be zero)
busy <= u && v; // We're still busy...
// Repeatedly subtract smaller number from larger one
if (v <= u)
u <= u - v;
else if (u < v)
v <= v - u;
if (load) // Load new problem when high
begin
u <= initial_u;
v <= initial_v;
busy <= 1;
end
end
endmodule
Visual Basic
Works with Visual Basic 5. Works with Visual Basic 6. Works with VBA 6.5. Works with VBA 7.1.
Function GCD(ByVal a As Long, ByVal b As Long) As Long
Dim h As Long
If a Then
If b Then
Do
h = a Mod b
a = b
b = h
Loop While b
End If
GCD = Abs(a)
Else
GCD = Abs(b)
End If
End Function
Sub Main()
' testing the above function
Debug.Assert GCD(12, 18) = 6
Debug.Assert GCD(1280, 240) = 80
Debug.Assert GCD(240, 1280) = 80
Debug.Assert GCD(-240, 1280) = 80
Debug.Assert GCD(240, -1280) = 80
Debug.Assert GCD(0, 0) = 0
Debug.Assert GCD(0, 1) = 1
Debug.Assert GCD(1, 0) = 1
Debug.Assert GCD(3475689, 23566319) = 7
Debug.Assert GCD(123456789, 234736437) = 3
Debug.Assert GCD(3780, 3528) = 252
End Sub
Wortel
Operator
@gcd a b
Number expression
!#~kg a b
Iterative
&[a b] [@vars[t] @while b @:{t b b %a b a t} a]
Recursive
&{gcd a b} ?{b !!gcd b %a b @abs a}
x86 Assembly
Using GNU Assembler syntax:
.text
.global pgcd
pgcd:
push %ebp
mov %esp, %ebp
mov 8(%ebp), %eax
mov 12(%ebp), %ecx
push %edx
.loop:
cmp $0, %ecx
je .end
xor %edx, %edx
div %ecx
mov %ecx, %eax
mov %edx, %ecx
jmp .loop
.end:
pop %edx
leave
ret
XLISP
GCD is a built-in function.
If we wanted to reimplement it,
one (tail-recursive) way would be like this:
(defun greatest-common-divisor (x y) (if (= y 0) x (greatest-common-divisor y (mod x y)) ) )
XPL0
include c:\cxpl\codes;
func GCD(U, V); \Return the greatest common divisor of U and V
int U, V;
int T;
[while V do \Euclid's method
[T:= U; U:= V; V:= rem(T/V)];
return abs(U);
];
\Display the GCD of two integers entered on command line
IntOut(0, GCD(IntIn(8), IntIn(8)))
Yabasic
sub gcd(u, v)
local t
u = int(abs(u))
v = int(abs(v))
while(v)
t = u
u = v
v = mod(t, v)
wend
return u
end sub
print "Greatest common divisor: ", gcd(12345, 9876)
Z80 Assembly
Uses the iterative subtraction implementation of Euclid's algorithm, because the Z80 does not implement modulus or division opcodes.
; Inputs: a, b
; Outputs: a = gcd(a, b)
; Destroys: c
; Assumes: a and b are positive one-byte integers
gcd:
cp b
ret z ; while a != b
jr c, else ; if a > b
sub b ; a = a - b
jr gcd
else:
ld c, a ; Save a
ld a, b ; Swap b into a so we can do the subtraction
sub c ; b = b - a
ld b, a ; Put a and b back where they belong
ld a, c
jr gcd
zkl
This is a method on integers:
(123456789).gcd(987654321) //-->9
Using the gnu big num library (GMP):
var BN=Import("zklBigNum");
BN(123456789).gcd(987654321) //-->9
or
fcn gcd(a,b){ while(b){ t:=a; a=b; b=t%b } a.abs() }
ZX Spectrum Basic
10 FOR n=1 TO 3
20 READ a,b
30 PRINT "GCD of ";a;" and ";b;" = ";
40 GO SUB 70
50 NEXT n
60 STOP
70 IF b=0 THEN PRINT ABS (a): RETURN
80 LET c=a: LET a=b: LET b=FN m(c,b): GO TO 70
90 DEF FN m(a,b)=a-INT (a/b)*b
100 DATA 12,16,22,33,45,67