Loops/Nested

Loops/Nested
You are encouraged to solve this task according to the task description, using any language you may know.

Show a nested loop which searches a two-dimensional array filled with random numbers uniformly distributed over $[1,\ldots ,20]$.

The loops iterate rows and columns of the array printing the elements until the value $20$ is met.

Specifically, this task also shows how to break out of nested loops.

Related tasks

•   Loop over multiple arrays simultaneously
•   Loops/Break
•   Loops/Continue
•   Loops/Do-while
•   Loops/Downward for
•   Loops/For
•   Loops/For with a specified step
•   Loops/Foreach
•   Loops/Increment loop index within loop body
•   Loops/Infinite
•   Loops/N plus one half
•   Loops/Nested
•   Loops/While
•   Loops/with multiple ranges
•   Loops/Wrong ranges

11l

[[Int]] mat
L 10
   mat [+]= (1..10).map(x -> random:(1..20))

L(row) mat
   L(el) row
      print(el, end' ‘ ’)
      I el == 20
         L(row).break

360 Assembly

*        Loop nested               12/08/2015 
LOOPNEST CSECT
         USING  LOOPNEST,R12
         LR     R12,R15
BEGIN    LA     R6,0               i
         LA     R8,1
         LA     R9,20
LOOPI1   BXH    R6,R8,ELOOPI1      do i=1 to hbound(x,1)
         LA     R7,0               j
         LA     R10,1
         LA     R11,20
LOOPJ1   BXH    R7,R10,ELOOPJ1     do j=1 to hbound(x,2)
         L      R5,RANDSEED        n
         M      R4,=F'397204094'   r4r5=n*const
         D      R4,=X'7FFFFFFF'    r5=r5 div (2^31-1)
         ST     R4,RANDSEED        r4=r5 mod (2^31-1) ; n=r4
         LR     R5,R4              r5=n
         LA     R4,0
         D      R4,=F'20'          r5=n div nn; r4=n mod nn
         LR     R2,R4              r2=randint(nn) [0:nn-1]
         LA     R2,1(R2)           randint(nn)+1
         LR     R1,R6              i
         BCTR   R1,0
         MH     R1,=H'20'
         LR     R5,R7              j
         BCTR   R5,0
         AR     R1,R5
         SLA    R1,2
         ST     R2,X(R1)           x(i,j)=randint(20)+1
         B      LOOPJ1
ELOOPJ1  B      LOOPI1
ELOOPI1  MVC    MVCZ,=CL80' '
         LA     R6,0               i
         LA     R8,1
         LA     R9,20
LOOPI2   BXH    R6,R8,ELOOPI2      do i=1 to hbound(x,1)
         LA     R7,0               j
         LA     R10,1
         LA     R11,20
LOOPJ2   BXH    R7,R10,ELOOPJ2     do j=1 to hbound(x,2)
         LR     R1,R6
         BCTR   R1,0
         MH     R1,=H'20'
         LR     R5,R7
         BCTR   R5,0
         AR     R1,R5
         SLA    R1,2
         L      R5,X(R1)           x(i,j)
         LR     R2,R5
         LA     R3,MVCZ
         AH     R3,MVCI
         XDECO  R2,XDEC
         MVC    0(4,R3),XDEC+8
         LH     R3,MVCI
         LA     R3,4(R3)
         STH    R3,MVCI
         L      R5,X(R1)
         C      R5,=F'20'          if x(i,j)=20 
         BE     ELOOPI2            then exit
         B      LOOPJ2
ELOOPJ2  XPRNT  MVCZ,80
         MVC    MVCI,=H'0'
         MVC    MVCZ,=CL80' '
         B      LOOPI2
ELOOPI2  XPRNT  MVCZ,80
RETURN   XR     R15,R15
         BR     R14
X        DS     400F
MVCZ     DS     CL80
MVCI     DC     H'0'
XDEC     DS     CL16
RANDSEED DC     F'16807'           running n
         YREGS  
         END    LOOPNEST

Output:

   3   4   1  11  13  17  11   9   8   2  15  19  16  18   1   9   7  16  12   3
  11  13  13   6  13  19   9  18  11   4   7   8   6   7   2  10  14   4   5   1
  16  14  13   6  11  20

Action!

PROC Main()
  DEFINE PTR="CARD"
  BYTE i,j,found
  PTR ARRAY a(10)
  BYTE ARRAY tmp,
    a0(10),a1(10),a2(10),a3(10),a4(10),
    a5(10),a6(10),a7(10),a8(10),a9(10)

  a(0)=a0 a(1)=a1 a(2)=a2 a(3)=a3 a(4)=a4
  a(5)=a5 a(6)=a6 a(7)=a7 a(8)=a8 a(9)=a9

  FOR j=0 TO 9
  DO
    tmp=a(j)
    FOR i=0 TO 9
    DO
      tmp(i)=Rand(20)+1
    OD
  OD

  found=0
  FOR j=0 TO 9
  DO
    tmp=a(j)
    FOR i=0 TO 9
    DO
      PrintB(tmp(i)) Put(32)
      IF tmp(i)=20 THEN
        found=1 EXIT
      FI
    OD
    IF found THEN
      EXIT
    FI
    PutE()
  OD
RETURN

Output:

Screenshot from Atari 8-bit computer

12 10 16 15 19 7 1 18 3 11
18 3 7 12 18 17 16 12 14 7
14 5 19 8 9 4 6 12 12 2
15 9 9 1 17 17 2 8 8 14
2 14 14 5 5 6 20

Ada

with Ada.Text_IO;  use Ada.Text_IO;
with Ada.Numerics.Discrete_Random;

procedure Test_Loop_Nested is
   type Value_Type is range 1..20;
   package Random_Values is new Ada.Numerics.Discrete_Random (Value_Type);
   use Random_Values;
   Dice : Generator;
   A : array (1..10, 1..10) of Value_Type :=
          (others => (others => Random (Dice)));
begin

Outer :
   for I in A'Range (1) loop
      for J in A'Range (2) loop
         Put (Value_Type'Image (A (I, J)));
         exit Outer when A (I, J) = 20;
      end loop;
      New_Line;
   end loop Outer;
end Test_Loop_Nested;

Sample output:

 16 3 1 17 13 5 4 2 19 1
 5 5 17 15 17 2 5 5 17 13
 16 10 10 20

ALGOL 60

Works with: ALGOL 60 version OS/360

'BEGIN' 'COMMENT' Loops/Nested - ALGOL60 - 19/06/2018;
  'INTEGER' SEED;
  'INTEGER' 'PROCEDURE' RANDOM(N);
  'VALUE' N; 'INTEGER' N;
  'BEGIN'
    SEED:=(SEED*19157+12347) '/' 21647;
    RANDOM:=SEED-(SEED '/' N)*N+1
  'END' RANDOM;
  'INTEGER' 'ARRAY' A(/1:10,1:10/);
  'INTEGER' I,J;
  SEED:=31569;
  'FOR' I:=1 'STEP' 1 'UNTIL' 10 'DO'
    'FOR' J:=1 'STEP' 1 'UNTIL' 10 'DO'
      A(/I,J/):=RANDOM(20);
  SYSACT(1,6,120);SYSACT(1,8,60);SYSACT(1,12,1);'COMMENT' open print;
  'FOR' I:=1 'STEP' 1 'UNTIL' 10 'DO'
    'FOR' J:=1 'STEP' 1 'UNTIL' 10 'DO' 'BEGIN'
      OUTINTEGER(1,A(/I,J/));
      'IF' A(/I,J/)=20 'THEN' 'GOTO' LAB;
	'END';
LAB:
'END'

Output:

        +19           +5           +1           +4          +17           +6           +2          +18          +12  
         +3          +13           +6           +8           +6          +10           +9          +15          +20  

ALGOL 68

Translation of: C

- note: This specimen retains the original C coding style.

Works with: ALGOL 68 version Standard - no extensions to language used

Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

Works with: ELLA ALGOL 68 version Any (with appropriate job cards)

main: (
    [10][10]INT a; INT i, j;

    FOR i FROM LWB a TO UPB a DO
        FOR j FROM LWB a[i] TO UPB a[i] DO
            a[i][j] := ENTIER (random * 20 + 1)
        OD
    OD ;
    FOR i FROM LWB a TO UPB a DO
        FOR j FROM LWB a[i] TO UPB a[i] DO
            print(whole(a[i][j], -3));
            IF a[i][j] = 20 THEN
                GO TO xkcd com 292 # http://xkcd.com/292/ #
            FI
        OD;
        print(new line)
    OD;
xkcd com 292:
    print(new line)
)

Sample output:

  8 14 17  6 18  1  1  7  9  6
  8  9  1 15  3  1 10 19  6  7
 12 20

Amazing Hopper

#include <jambo.h>

#define DIMS  10
Main
   Unset decimal
   Dim (DIMS,DIMS) as ceil rand (20,t)

   Set decimal '0'
   Printnl ("ORIGINAL MATRIX:\n", Just right (3, Str(t)), "\n")

   aux=0
   Loop for ( i=1, #(i<=DIMS && aux<>20 ), ++i)
        Loop for ( j=1, #(j<=DIMS), ++j)
             When ( Equals ( 20, [i,j] Get 't' ---Copy to 'aux'---) ) { Break }
             /*
             Also: When( #( ((aux:= (t[i,j])) == 20) ) ) { Break }
             */
             Just right (3, Str(aux)), Print only if ( #(DIMS-j), "," )
        Next
        Prnl
   Next
   Printnl ("\nFOUNDED: ", i,",",j," = ",aux)
End

Output:

ORIGINAL MATRIX:
 16,  5, 15, 19, 14, 15, 12, 15, 10, 19
  6,  8, 17,  1,  5, 13, 14,  4, 15,  5
 10, 17,  8,  4,  9, 19, 14, 17,  7,  4
  7,  2,  8,  1, 20,  1, 15, 12, 16,  4
 10,  2, 12,  7,  3, 16, 19, 16, 19, 14
  1,  9, 11,  9, 12, 19,  7,  6, 16, 13
  9,  2, 15, 16,  2, 15, 17, 17,  7, 13
 20, 17, 15, 12,  3, 17,  8,  2, 13,  7
 15, 13, 15,  6,  2,  7,  5,  8, 12, 20
  1, 20,  1, 16, 16,  2, 10, 12, 19, 17


 16,  5, 15, 19, 14, 15, 12, 15, 10, 19
  6,  8, 17,  1,  5, 13, 14,  4, 15,  5
 10, 17,  8,  4,  9, 19, 14, 17,  7,  4
  7,  2,  8,  1,

FOUNDED: 4,5 = 20

AppleScript

AppleScript has exit repeat to break out of a single loop prematurely, but nothing specifically for nested loops. So either exit repeat must be used twice …

on loopDemo(array, stopVal)
    set out to {}
    repeat with i from 1 to (count array)
        set inRow to item i of array
        set outRow to {}
        repeat with j from 1 to (count inRow)
            set n to item j of inRow
            set end of outRow to n
            if (n = stopVal) then exit repeat # <--
        end repeat
        set end of out to outRow
        if (n = stopVal) then exit repeat # <--
    end repeat
    
    return out
end loopDemo

… or of course one or both loops can be specified to terminate at the critical juncture anyway …

on loopDemo(array, stopVal)
    set out to {}
    repeat with i from 1 to (count array)
        set inRow to item i of array
        set len to (count inRow)
        set n to beginning of inRow
        set outRow to {n}
        set j to 2
        repeat until ((j > len) or (n = stopVal)) # <--
            set n to item j of inRow
            set end of outRow to n
            set j to j + 1
        end repeat
        set end of out to outRow
        if (n = stopVal) then exit repeat # <--
    end repeat
    
    return out
end loopDemo

… or, with the process in a dedicated handler, it can be returned from directly at any point:

on loopDemo(array, stopVal)
    set out to {}
    repeat with i from 1 to (count array)
        set inRow to item i of array
        set outRow to {}
        repeat with j from 1 to (count inRow)
            set n to item j of inRow
            set end of outRow to n
            if (n = stopVal) then return out & {outRow} # <--
        end repeat
        set end of out to outRow
    end repeat
    
    return out
end loopDemo

Demo:

local array, stopVal, row
set array to {}
set stopVal to 20
repeat 10 times
    set row to {}
    repeat 10 times
        set end of row to (random number from 1 to stopVal)
    end repeat
    set end of array to row
end repeat
loopDemo(array, stopVal) -- Any of the handlers above.

Output:

{{15, 8, 9, 8, 9, 9, 10, 16, 3, 6}, {11, 3, 14, 18, 17, 1, 16, 15, 14, 7}, {4, 20}}

ARM Assembly

Works with: as version Raspberry Pi

/* ARM assembly Raspberry PI  */
/*  program loopnested.s   */
 
/************************************/
/* Constantes                       */
/************************************/
.equ STDOUT, 1     @ Linux output console
.equ EXIT,   1     @ Linux syscall
.equ WRITE,  4     @ Linux syscall


.equ NBVALUECOL,      10
.equ NBLIGNES,        10
.equ MAXVALUE,        20

/*********************************/
/* Initialized data              */
/*********************************/
.data
sMessResult:        .ascii " "
sMessValeur:        .fill 11, 1, ' '            @ size => 11
szCarriageReturn:   .asciz "\n"

 
.align 4
iGraine:  .int 314159

/*********************************/
/* UnInitialized data            */
/*********************************/
.bss  
tiValues:                .skip  4 * NBVALUECOL * NBLIGNES
/*********************************/
/*  code section                 */
/*********************************/
.text
.global main 
main:                                             @ entry of program 
    ldr r3,iAdrtiValues
    mov r4,#0                                     @ loop indice
    mov r5,#0
    mov r7,#4 * NBVALUECOL
1:                                                @ begin loop 1
    mov r0,#MAXVALUE + 1
    bl genereraleas                               @ result 0 to MAXVALUE
    
    mul r6,r5,r7
    add r6,r4,lsl #2
    str r0,[r3,r6]
    add r4,#1
    cmp r4,#NBVALUECOL
    blt 1b
    mov r4,#0
    add r5,#1
    cmp r5,#NBLIGNES
    blt 1b

    mov r4,#0                                     @ loop indice
    mov r5,#0                                     @ total
    ldr r3,iAdrtiValues                           @ table values address
2:
    mul r6,r5,r7
    add r6,r4,lsl #2
    ldr r0,[r3,r6]
    ldr r1,iAdrsMessValeur                        @ display value
    bl conversion10                               @ call conversion decimal
    mov r1,#0
    ldr r0,iAdrsMessResult
    strb r1,[r0,#4]
    ldr r0,iAdrsMessResult
    bl affichageMess                              @ display message
    ldr r0,[r3,r6]
    cmp r0,#MAXVALUE
    beq 3f
    add r4,#1
    cmp r4,#NBVALUECOL
    blt 2b
    ldr r0,iAdrszCarriageReturn
    bl affichageMess                              @ display message
    mov r4,#0
    add r5,#1
    cmp r5,#NBLIGNES
    blt 2b
    b 100f
3:
    ldr r0,iAdrszCarriageReturn
    bl affichageMess                              @ display message

100:                                              @ standard end of the program 
    mov r0, #0                                    @ return code
    mov r7, #EXIT                                 @ request to exit program
    svc #0                                        @ perform the system call
 
iAdrsMessValeur:          .int sMessValeur
iAdrszCarriageReturn:     .int szCarriageReturn
iAdrsMessResult:          .int sMessResult
iAdrtiValues:             .int tiValues

/******************************************************************/
/*     display text with size calculation                         */ 
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
    push {r0,r1,r2,r7,lr}                          @ save  registres
    mov r2,#0                                      @ counter length 
1:                                                 @ loop length calculation 
    ldrb r1,[r0,r2]                                @ read octet start position + index 
    cmp r1,#0                                      @ if 0 its over 
    addne r2,r2,#1                                 @ else add 1 in the length 
    bne 1b                                         @ and loop 
                                                   @ so here r2 contains the length of the message 
    mov r1,r0                                      @ address message in r1 
    mov r0,#STDOUT                                 @ code to write to the standard output Linux 
    mov r7, #WRITE                                 @ code call system "write" 
    svc #0                                         @ call systeme 
    pop {r0,r1,r2,r7,lr}                           @ restaur des  2 registres */ 
    bx lr                                          @ return  
/******************************************************************/
/*     Converting a register to a decimal unsigned                */ 
/******************************************************************/
/* r0 contains value and r1 address area   */
/* r0 return size of result (no zero final in area) */
/* area size => 11 bytes          */
.equ LGZONECAL,   10
conversion10:
    push {r1-r4,lr}                                 @ save registers 
    mov r3,r1
    mov r2,#LGZONECAL
 
1:                                                  @ start loop
    bl divisionpar10U                               @ unsigned  r0 <- dividende. quotient ->r0 reste -> r1
    add r1,#48                                      @ digit
    strb r1,[r3,r2]                                 @ store digit on area
    cmp r0,#0                                       @ stop if quotient = 0 
    subne r2,#1                                     @ else previous position
    bne 1b                                          @ and loop
                                                    @ and move digit from left of area
    mov r4,#0
2:
    ldrb r1,[r3,r2]
    strb r1,[r3,r4]
    add r2,#1
    add r4,#1
    cmp r2,#LGZONECAL
    ble 2b
                                                      @ and move spaces in end on area
    mov r0,r4                                         @ result length 
    mov r1,#' '                                       @ space
3:
    strb r1,[r3,r4]                                   @ store space in area
    add r4,#1                                         @ next position
    cmp r4,#LGZONECAL
    ble 3b                                            @ loop if r4 <= area size
 
100:
    pop {r1-r4,lr}                                    @ restaur registres 
    bx lr                                             @return
 
/***************************************************/
/*   division par 10   unsigned                    */
/***************************************************/
/* r0 dividende   */
/* r0 quotient */	
/* r1 remainder  */
divisionpar10U:
    push {r2,r3,r4, lr}
    mov r4,r0                                          @ save value
    //mov r3,#0xCCCD                                   @ r3 <- magic_number lower  raspberry 3
    //movt r3,#0xCCCC                                  @ r3 <- magic_number higter raspberry 3
    ldr r3,iMagicNumber                                @ r3 <- magic_number    raspberry 1 2
    umull r1, r2, r3, r0                               @ r1<- Lower32Bits(r1*r0) r2<- Upper32Bits(r1*r0) 
    mov r0, r2, LSR #3                                 @ r2 <- r2 >> shift 3
    add r2,r0,r0, lsl #2                               @ r2 <- r0 * 5 
    sub r1,r4,r2, lsl #1                               @ r1 <- r4 - (r2 * 2)  = r4 - (r0 * 10)
    pop {r2,r3,r4,lr}
    bx lr                                              @ leave function 
iMagicNumber:  	.int 0xCCCCCCCD
/***************************************************/
/*   Generation random number                  */
/***************************************************/
/* r0 contains limit  */
genereraleas:
    push {r1-r4,lr}                                    @ save registers 
    ldr r4,iAdriGraine
    ldr r2,[r4]
    ldr r3,iNbDep1
    mul r2,r3,r2
    ldr r3,iNbDep1
    add r2,r2,r3
    str r2,[r4]                                        @ maj de la graine pour l appel suivant 
    cmp r0,#0
    beq 100f
    mov r1,r0                                          @ divisor
    mov r0,r2                                          @ dividende
    bl division
    mov r0,r3                                          @ résult = remainder
  
100:                                                   @ end function
    pop {r1-r4,lr}                                     @ restaur registers
    bx lr                                              @ return
/*****************************************************/
iAdriGraine: .int iGraine
iNbDep1: .int 0x343FD
iNbDep2: .int 0x269EC3 
/***************************************************/
/* integer division unsigned                       */
/***************************************************/
division:
    /* r0 contains dividend */
    /* r1 contains divisor */
    /* r2 returns quotient */
    /* r3 returns remainder */
    push {r4, lr}
    mov r2, #0                                         @ init quotient
    mov r3, #0                                         @ init remainder
    mov r4, #32                                        @ init counter bits
    b 2f
1:                                                     @ loop 
    movs r0, r0, LSL #1                                @ r0 <- r0 << 1 updating cpsr (sets C if 31st bit of r0 was 1)
    adc r3, r3, r3                                     @ r3 <- r3 + r3 + C. This is equivalent to r3 ? (r3 << 1) + C 
    cmp r3, r1                                         @ compute r3 - r1 and update cpsr 
    subhs r3, r3, r1                                   @ if r3 >= r1 (C=1) then r3 <- r3 - r1 
    adc r2, r2, r2                                     @ r2 <- r2 + r2 + C. This is equivalent to r2 <- (r2 << 1) + C 
2:
    subs r4, r4, #1                                    @ r4 <- r4 - 1 
    bpl 1b                                             @ if r4 >= 0 (N=0) then loop
    pop {r4, lr}
    bx lr

Arturo

printTable: function [tbl][
    ; wrapping the nested loop in a function
    ; allows us to use return to exit all of the loops
    ; since `break` only exits the inner loop
    loop 0..dec size tbl 'x [
        loop 0..dec size tbl\[x] 'y [
            prints pad to :string tbl\[x]\[y] 2
            if tbl\[x]\[y] = 20 -> return ø
            prints ", "
        ]
        print ""
    ]
]

a: []
loop 1..10 'x [
    row: []
    loop 1..10 'y [
        'row ++ random 1 20
    ]
    'a ++ @[row]
]

printTable a

Output:

 4, 12, 12, 17,  7, 13, 14, 10, 14,  9, 
17, 12, 16, 10, 11, 13,  8, 13, 17,  3, 
 6, 17,  3, 18,  2, 16,  7,  9, 19,  9, 
19, 11, 11, 14,  5, 14, 18, 17, 19, 15, 
17, 16,  8,  3, 14, 17,  5,  6,  8,  1, 
 8,  4,  9, 10, 16, 16,  4, 15, 10, 18, 
 5,  8, 15, 19,  7,  8,  2,  6, 10,  8, 
 4, 17, 15, 18, 14,  2, 20

AutoHotkey

Loop, 10
{
  i := A_Index
  Loop, 10
  {
    j := A_Index
    Random, a%i%%j%, 1, 20
  }
}

Loop, 10
{
  i := A_Index
  Loop, 10
  {
    j := A_Index
    If (a%i%%j% == 20)
      Goto finish
  }
}

finish:
  MsgBox % "a[" . i . "][" . j . "]" is 20
Return

AWK

To break from two loops, this program uses two break statements and one b flag.

BEGIN {
	rows = 5
	columns = 5

	# Fill ary[] with random numbers from 1 to 20.
	for (r = 1; r <= rows; r++) {
		for (c = 1; c <= columns; c++)
			ary[r, c] = int(rand() * 20) + 1
	}

	# Find a 20.
	b = 0
	for (r = 1; r <= rows; r++) {
		for (c = 1; c <= columns; c++) {
			v = ary[r, c]
			printf " %2d", v
			if (v == 20) {
				print
				b = 1
				break
			}
		}
		if (b) break
		print
	}
}

BASIC

Works with: QuickBasic version 4.5

DIM a(1 TO 10, 1 TO 10) AS INTEGER
CLS
FOR row = 1 TO 10
        FOR col = 1 TO 10
                a(row, col) = INT(RND * 20) + 1
        NEXT col
NEXT row

FOR row = LBOUND(a, 1) TO UBOUND(a, 1)
        FOR col = LBOUND(a, 2) TO UBOUND(a, 2)
                PRINT a(row, col)
                IF a(row, col) = 20 THEN END
        NEXT col
NEXT row

Applesoft BASIC

 1 C = 5
 2 R = 4
 3 C = C - 1:R = C - 1: DIM A(C,R)
 4  FOR J = 0 TO R: FOR I = 0 TO C:N = N + 1:A(I,J) = N: NEXT I,J
 5  FOR J = 0 TO R: FOR I = 0 TO C:X =  INT ( RND (1) * C):Y =  INT ( RND (1) * R):N = A(I,J):A(I,J) = A(X,Y):A(X,Y) = N: NEXT I,J
 6  FOR J = 0 TO R
 7      FOR I = 0 TO C
 8          PRINT S$A(I,J);:S$ = " "
 9          IF A(I,J) <  > 20 THEN  NEXT I,J

Commodore BASIC

We should END gracefully. (The Sinclair example below will produce an error on any Commodore machine.)

Also... What if no 20 is ever found?

10 dim a$(20,20):print "initializing...":print
20 for r=1 to 20:for c=1 to 20
30 a$(r,c)=chr$(int(rnd(1)*20)+1)
40 next c,r
50 rem now search array
60 for r=1 to 20:for c=1 to 20
70 e=asc(a$(r,c))
80 print "(";r;","c;") =";e
90 if e=20 then print "found 20. stopping search.":end
100 next c,r
110 print "search complete. no 20 found.":end

Sinclair ZX81 BASIC

Works with 1k of RAM.

A couple of points to note: (1) since the values we want are small enough to fit into an unsigned byte, we cast them to characters and store them in an array of strings—thereby using only a fifth of the storage space that an array of numbers would take up; (2) the GOTO statement in line 100 breaks out of both the enclosing loops and also, since its target is higher than any line number in the program, causes execution to terminate normally.

 10 DIM A$(20,20)
 20 FOR I=1 TO 20
 30 FOR J=1 TO 20
 40 LET A$(I,J)=CHR$ (1+INT (RND*20))
 50 NEXT J
 60 NEXT I
 70 FOR I=1 TO 20
 80 FOR J=1 TO 20
 90 PRINT CODE A$(I,J);" ";
100 IF CODE A$(I,J)=20 THEN GOTO 130
110 NEXT J
120 NEXT I

BASIC256

dim a(20, 20)

for i = 0 to 19
	for j = 0 to 19
		a[i, j] = int(rand * 20) + 1
	next j
next i

for i = 0 to 19
	for j = 0 to 19
		print a[i, j];" ";
		if a[i, j] = 20 then end
	next j
next i

end

BBC BASIC

Works with: BBC BASIC for Windows

      DIM array(10,10)
      FOR row% = 0 TO 10
        FOR col% = 0 TO 10
          array(row%,col%) = RND(20) + 1
        NEXT
      NEXT row%
      FOR row% = 0 TO 10
        FOR col% = 0 TO 10
          PRINT "row "; row%, "col ";col%, "value "; array(row%,col%)
          IF array(row%,col%) = 20 EXIT FOR row%
        NEXT
      NEXT row%

EXIT FOR can jump out of multiple nested loops by specifying a control variable.

bc

Arrays have only one dimension, so we use a[i * c + j] instead of a[i, j].

Translation of: AWK

s = 1	/* Seed of the random number generator */

/* Random number from 1 to 20. */
define r() {
	auto r
	while (1) {
		/*
		 * Formula (from POSIX) for random numbers of low
		 * quality, from 0 to 32767.
		 */
		s = (s * 1103515245 + 12345) % 4294967296
		r = (s / 65536) % 32768

		/* Prevent modulo bias. */
		if (r >= 32768 % 20) break
	}
	return ((r % 20) + 1)
}

r = 5	/* Total rows */
c = 5	/* Total columns */

/* Fill array a[] with random numbers from 1 to 20. */
for (i = 0; i < r; i++) {
	for (j = 0; j < c; j++) {
		a[i * c + j] = r()
	}
}

/* Find a 20. */
b = 0
for (i = 0; i < r; i++) {
	for (j = 0; j < c; j++) {
		v = a[i * c + j]
		v	/* Print v and a newline. */
		if (v == 20) {
			b = 1
			break
		}
	}
	if (b) break
	/* Print "==" and a newline. */
	"==
"
}
quit

C

Using goto (note: gotos are considered harmful):

#include <stdlib.h>
#include <time.h>
#include <stdio.h>

int main() {
    int a[10][10], i, j;

    srand(time(NULL));
    for (i = 0; i < 10; i++)
        for (j = 0; j < 10; j++)
            a[i][j] = rand() % 20 + 1;

    for (i = 0; i < 10; i++) {
        for (j = 0; j < 10; j++) {
            printf(" %d", a[i][j]);
            if (a[i][j] == 20)
                goto Done;
        }
        printf("\n");
    }
Done:
    printf("\n");
    return 0;
}

Using break, the preferred alternative to goto

#include <stdlib.h>
#include <time.h>
#include <stdio.h>
 
int main() {
    int a[10][10], i, j;
 
    srand(time(NULL));
    for (i = 0; i < 10; i++)
        for (j = 0; j < 10; j++)
            a[i][j] = rand() % 20 + 1;
 
    for (i = 0; i < 10; i++) {
        for (j = 0; j < 10; j++) {
            printf(" %d", a[i][j]);
            if (a[i][j] == 20)
                break;
        }
        if (a[i][j] == 20)
            break;
        printf("\n");
    }
    printf("\n");
    return 0;
}

C#

Uses goto as C# has no way to break from multiple loops

using System;

class Program {
    static void Main(string[] args) {
        int[,] a = new int[10, 10];
        Random r = new Random();

        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 10; j++) {
                a[i, j] = r.Next(0, 21) + 1;
            }
        }
        
        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 10; j++) {
                Console.Write(" {0}", a[i, j]);
                if (a[i, j] == 20) {
                    goto Done;
                }
            }
            Console.WriteLine();
        }
    Done:
        Console.WriteLine();
    }
}

Same using Linq :

using System;
using System.Collections.Generic;
using System.Linq;

class Program {
    static void Main(string[] args) {
            int[,] a = new int[10, 10];
            Random r = new Random();

            // prepare linq statement with two 'from' which makes nested loop
            var pairs = from i in Enumerable.Range(0, 10)
                        from j in Enumerable.Range(0, 10)
                        select new { i = i, j = j};

            // iterates through the full nested loop with a sigle foreach statement
            foreach (var p in pairs)
            {
                a[p.i, p.j] = r.Next(0, 21) + 1;
            }

            // iterates through the nested loop until find element = 20
            pairs.Any(p => { Console.Write(" {0}", a[p.i, p.j]); return a[p.i, p.j] == 20; });
            Console.WriteLine();
    }
}

C++

Lambda call:

Works with: C++11

#include<cstdlib>
#include<ctime>
#include<iostream>

using namespace std;
int main()
{
    int arr[10][10];
    srand(time(NULL));
    for(auto& row: arr)
        for(auto& col: row)
            col = rand() % 20 + 1;

    ([&](){
       for(auto& row : arr)
           for(auto& col: row)
           {
               cout << col << endl;
               if(col == 20)return;
           }
    })();
    return 0;
}

Goto statement:

Works with: C++11

#include<cstdlib>
#include<ctime>
#include<iostream>

using namespace std;
int main()
{
    int arr[10][10];
    srand(time(NULL));
    for(auto& row: arr)
        for(auto& col: row)
            col = rand() % 20 + 1;

    for(auto& row : arr) {
        for(auto& col: row) {
            cout << ' ' << col;
            if (col == 20) goto out;
        }
        cout << endl;
    }
    out:

    return 0;
}

Chapel

use Random;

var nums:[1..10, 1..10] int;
var rnd = new RandomStream();

[ n in nums ] n = floor(rnd.getNext() * 21):int;
delete rnd;

// this shows a clumsy explicit way of iterating, to actually create nested loops: 
label outer for i in nums.domain.dim(1) {
        for j in nums.domain.dim(2) {
                write(" ", nums(i,j));
                if nums(i,j) == 20 then break outer;
        }
        writeln();
}

Clojure

We explicitly return a status flag from the inner loop:

(ns nested)

(defn create-matrix [width height]
  (for [_ (range width)]
    (for [_ (range height)]
      (inc (rand-int 20)))))

(defn print-matrix [matrix]
  (loop [[row & rs] matrix]
    (when (= (loop [[x & xs] row]
               (println x)
               (cond (= x 20) :stop
                     xs (recur xs)
                     :else :continue))
             :continue)
      (when rs (recur rs)))))

(print-matrix (create-matrix 10 10))

COBOL

       IDENTIFICATION DIVISION.
       PROGRAM-ID. Nested-Loop.

       DATA DIVISION.
       LOCAL-STORAGE SECTION.
       78  Table-Size VALUE 10.
       01  Table-Area.
           03  Table-Row OCCURS Table-Size TIMES
                   INDEXED BY Row-Index.
               05  Table-Element PIC 99 OCCURS Table-Size TIMES
                   INDEXED BY Col-Index.

       01  Current-Time PIC 9(8).
       PROCEDURE DIVISION.
*          *> Seed RANDOM.
           ACCEPT Current-Time FROM TIME
           MOVE FUNCTION RANDOM(Current-Time) TO Current-Time

*          *> Put random numbers in the table.
*          *> The AFTER clause is equivalent to a nested PERFORM VARYING
*          *> statement.
           PERFORM VARYING Row-Index FROM 1 BY 1
                       UNTIL Table-Size < Row-Index
                   AFTER Col-Index FROM 1 BY 1
                       UNTIL Table-Size < Col-Index
               COMPUTE Table-Element (Row-Index, Col-Index) =
                   FUNCTION MOD((FUNCTION RANDOM * 1000), 20) + 1
           END-PERFORM

*          *> Search through table for 20.
*          *> Using proper nested loops.
           PERFORM VARYING Row-Index FROM 1 BY 1
                   UNTIL Table-Size < Row-Index
               PERFORM VARYING Col-Index FROM 1 BY 1
                       UNTIL Table-Size < Col-Index
                   IF Table-Element (Row-Index, Col-Index) = 20
                       EXIT PERFORM
                   ELSE
                       DISPLAY Table-Element (Row-Index, Col-Index)
                   END-IF
               END-PERFORM
           END-PERFORM

           GOBACK
           .

ColdFusion

<Cfset RandNum = 0>
<Cfloop condition="randNum neq 20">
  <Cfloop from="1" to="5" index="i">
    <Cfset randNum = RandRange(1, 20)>
    <Cfoutput>#randNum# </Cfoutput>
    <Cfif RandNum eq 20><cfbreak></Cfif>
  </Cfloop>
  <br>
</Cfloop>

Common Lisp

(let ((a (make-array '(10 10))))
  (dotimes (i 10)
    (dotimes (j 10)
      (setf (aref a i j) (1+ (random 20)))))
   
  (block outer
    (dotimes (i 10)
      (dotimes (j 10)
        (princ " ")
        (princ (aref a i j))
        (if (= 20 (aref a i j))
            (return-from outer)))
      (terpri))
    (terpri)))

D

import std.stdio, std.random;

void main() {
    int[10][10] mat;
    foreach (ref row; mat)
        foreach (ref item; row)
            item = uniform(1, 21);

    outer:
    foreach (row; mat)
        foreach (item; row) {
            write(item, ' ');
            if (item == 20)
                break outer;
        }

    writeln();
}

dc

A single Q command can break multiple nested loops.

Translation of: bc

1 ss  [Seed of the random number generator.]sz

[*
 * lrx -- (number)
 * Push a random number from 1 to 20.
 *]sz
[
 [                [If preventing modulo bias:]sz
  sz               [Drop this random number.]sz
  lLx              [Loop.]sz
 ]SI
 [                [Loop:]sz
  [*
   * Formula (from POSIX) for random numbers of low quality.
   * Push a random number from 0 to 32767.
   *]sz
  ls 1103515245 * 12345 + 4294967296 % ss
  ls 65536 / 32768 %

  d 32768 20 % >I  [Prevent modulo bias.]sz
 ]d SL x
 20 % 1 +         [Be from 1 to 20.]sz
 LLsz LIsz        [Restore L, I.]sz
]sr


5 sb           [b = Total rows]sz
5 sc           [c = Total columns]sz

[Fill array a[] with random numbers from 1 to 20.]sz
[              [Inner loop for j:]sz
 lrx            [Push random number.]sz
 li lc * lj +   [Push index of a[i, j].]sz
 :a             [Put in a[].]sz
 lj 1 + d sj    [j += 1]sz
 lc >I          [Loop while c > j.]sz
]sI
[              [Outer loop for i:]sz
 0 d sj         [j = 0]sz
 lc >I          [Enter inner loop.]sz
 li 1 + d si    [i += 1]sz
 lb >L          [Loop while b > i.]sz
]sL
0 d si         [i = 0]sz
lb >L          [Enter outer loop.]sz

[Find a 20.]sz
[              [If detecting a 20:]sz
 li lj + 3 + Q  [Break outer loop.]sz
]sD
[              [Inner loop for j:]sz
 li lc * lj +   [Push index of a[i,j].]sz
 ;a             [Push value from a[].]sz
 p              [Print value and a newline.]sz
 20 =D          [Detect a 20.]sz
 lj 1 + d sj    [j += 1]sz
 lc >I          [Loop while c > j.]sz
]sI
[              [Outer loop for i:]sz
 0 d sj         [j = 0]sz
 lc >I          [Enter inner loop.]sz
 [==
]P              [Print "==" and a newline.]sz
 li 1 + d si    [i += 1]sz
 lb >L          [Loop while b > i.]sz
]sL
0 d si         [i = 0]sz
lb >L          [Enter outer loop.]sz

In this program, li lj + 3 + Q breaks both the inner loop and the outer loop. We must count how many levels of string execution to break. Our loops use tail recursion, so each iteration is a level of string execution. We have i + 1 calls to outer loop L, and j + 1 calls to inner loop I, and 1 call to condition D; so we break i + j + 3 levels with li lj + 3 + Q.

Delphi/Pascal

var
  matrix: array[1..10,1..10] of Integer;
  row, col: Integer;
  broken: Boolean;
begin
  // Launch random number generator
  randomize;
  // Filling matrix with random numbers
  for row := 1 to 10 do
    for col := 1 to 10 do
      matrix[row, col] := Succ(Random(20));
  // Displaying values one by one, until at the end or reached number 20
  Broken := False;
  for row := 1 to 10 do
  begin
    for col := 1 to 10 do
    begin
      ShowMessage(IntToStr(matrix[row, col]));
      if matrix[row, col] = 20 then
      begin
        Broken := True;
        break;
      end;
    end;
    if Broken then break;
  end;
end;

Dyalect

There is no direct way to break out of a nested loop in Dyalect, goto is also not supported, however the desired effect can be achieved by placing a nested loop in an expression context and make it return true if we need to break out of the parent loop:

let array = [[2, 12, 10, 4], [18, 11, 20, 2]]
 
for row in array {
    break when { 
        for element in row {
            print("\(element)")
            if element == 20 {
                break true
            }
        }
    }
}
print("*Done")

Output:

2
12
10
4
18
11
20
*Done

E

def array := accum [] for i in 1..5 { _.with(accum [] for i in 1..5 { _.with(entropy.nextInt(20) + 1) }) }

escape done {
    for row in array {
        for x in row {
            print(`$x$\t`)
            if (x == 20) {
                done()
            }
        }
        println()
    }
}
println("done.")

EasyLang

arr[][] = [ [ 2 12 10 4 ] [ 18 11 20 2 ] ]
for i to len arr[][]
   for j to len arr[i][]
      if arr[i][j] = 20
         print "20 at " & i & "," & j
         break 2
      .
   .
.

EchoLisp

(lib 'math) ;; for 2D-arrays
(define array (build-array 42 42 (lambda(i j) (1+ (random 20)))))
 → array

;;
(for* ((row array) (aij row)) (write aij) #:break (= aij 20))
  → 9 8 11 1 14 11 1 9 16 1 10 5 5 6 5 4 13 17 14 13 6 10 16 4 8 5 1 17 16 19 4 6 18 1 15 3 4 13 19
  6 12 5 5 17 19 16 3 7 2 15 16 14 16 16 19 18 14 16 6 18 14 17 20

Elixir

Works with: Elixir version 1.2

defmodule Loops do
  def nested do
    list = Enum.shuffle(1..20) |> Enum.chunk(5)
    IO.inspect list, char_lists: :as_lists
    try do
      nested(list)
    catch
      :find -> IO.puts "done"
    end
  end
  
  def nested(list) do
    Enum.each(list, fn row ->
      Enum.each(row, fn x ->
        IO.write "#{x} "
        if x == 20, do: throw(:find)
      end)
      IO.puts ""
    end)
  end
end

Loops.nested

Sample output:

[[3, 11, 4, 15, 18], [8, 7, 12, 17, 9], [6, 20, 14, 1, 16], [2, 5, 10, 19, 13]]
3 11 4 15 18
8 7 12 17 9
6 20 done

used Enum.any?

list = Enum.shuffle(1..20) |> Enum.chunk(5)
IO.inspect list, char_lists: :as_lists
Enum.any?(list, fn row ->
  IO.puts ""
  Enum.any?(row, fn x ->
    IO.write "#{x} "
    x == 20
  end)
end)
IO.puts "done"

Sample output:

[[17, 15, 18, 14, 16], [5, 11, 10, 4, 2], [8, 20, 7, 19, 1], [6, 9, 3, 12, 13]]

17 15 18 14 16
5 11 10 4 2
8 20 done

Erlang

-module( loops_nested ).

-export( [task/0] ).

task() ->
       Size = 20,
       Two_dimensional_array = [random_array(Size) || _X <- lists:seq(1, Size)],
       print_until_found( [], 20, Two_dimensional_array ).



print_until_found( [], N, [Row | T] ) -> print_until_found( print_until_found_row(N, Row), N, T );
print_until_found( _Found, _N, _Two_dimensional_array ) -> io:fwrite( "~n" ).

print_until_found_row( _N, [] ) -> [];
print_until_found_row( N, [N | T] ) -> [N | T];
print_until_found_row( N, [H | T] ) ->
        io:fwrite( "~p ", [H] ),
        print_until_found_row( N, T ).

random_array( Size ) -> [random:uniform(Size) || _X <- lists:seq(1, Size)].

ERRE

DIM A%[10,10]                      ! in declaration part
.............
PRINT(CHR$(12);) !CLS
FOR ROW=1 TO 10 DO
   FOR COL=1 TO 10 DO
     A%[ROW,COL]=INT(RND(1)*20)+1  ! INT and RND are ERRE predeclared functions
                                   ! RND generates random numbers between 0 and 1
   END FOR
END FOR

FOR ROW=1 TO 10 DO
   FOR COL=1 TO 10 DO
     PRINT(A%[ROW,COL])
     EXIT IF A%[ROW,COL]=20
   END FOR
   EXIT IF A%[ROW,COL]=20  ! EXIT breaks the current loop only: you must repeat it,
                           ! use a boolean variable or a GOTO label statement
END FOR

Euphoria

sequence a
a = rand(repeat(repeat(20, 10), 10))

integer wantExit
wantExit = 0

for i = 1 to 10 do
    for j = 1 to 10 do
	printf(1, "%g ", {a[i][j]})
	if a[i][j] = 20 then
	    wantExit = 1
	    exit
	end if
    end for
    if wantExit then
	exit
    end if
end for

exit only breaks out of the innermost loop. A better way to do this would be a procedure.

F#

//Nigel Galloway: November 10th., 2017
let n = System.Random()
let g = Array2D.init 8 8 (fun _ _ -> 1+n.Next()%20)
Array2D.iter (fun n -> printf "%d " n) g; printfn ""
g |> Seq.cast<int> |> Seq.takeWhile(fun n->n<20) |> Seq.iter (fun n -> printf "%d " n)

Output:

3 7 5 8 7 5 12 14 6 10 7 8 4 8 10 2 12 16 9 19 14 10 1 1 14 2 8 18 1 1 6 19 5 16 15 16 11 19 19 17 3 9 9 15 14 12 20 18 14 8 5 12 20 14 5 14 7 5 15 13 5 15 14 13
3 7 5 8 7 5 12 14 6 10 7 8 4 8 10 2 12 16 9 19 14 10 1 1 14 2 8 18 1 1 6 19 5 16 15 16 11 19 19 17 3 9 9 15 14 12

Factor

Whenever you need to break out of iteration early in Factor, you almost always want to use find. find is a tail-recursive combinator that searches a sequence. Its base case is satisfied when its predicate quotation returns t.

USING: io kernel math.ranges prettyprint random sequences ;

10 [ 20 [ 20 [1,b] random ] replicate ] replicate    ! make a table of random values
[ [ dup pprint bl 20 = ] find nl drop ] find 2drop   ! print values until 20 is found

Alternatively, calling return from inside a with-return quotation allows one to break out of the quotation. This is similar to the way other languages do things: with an explicit break. This is less elegant in Factor because it introduces an additional quotation and involves continuations when they aren't strictly necessary (resulting in slower execution than find).

USING: continuations io kernel math.ranges prettyprint random
sequences ;

10 [ 20 [ 20 [1,b] random ] replicate ] replicate             ! make a table of random values
[
    [ [ dup pprint bl 20 = [ return ] when ] each nl ] each   ! print values until 20 is found
] with-return drop

Output:

19 5 19 14 15 14 17 16 4 11 17 3 19 10 2 1 8 13 2 6 
15 7 12 19 3 7 4 10 7 17 6 1 10 15 6 3 18 18 4 11 
20

Fantom

There is no specific way to break out of nested loops (such as a labelled break, or goto). Instead, we can use exceptions and a try-catch block.

class Main
{
  public static Void main ()
  {
    rows := 10
    cols := 10
    // create and fill an array of given size with random numbers
    Int[][] array := [,]
    rows.times
    {
      row := [,]
      cols.times { row.add(Int.random(1..20)) }
      array.add (row)
    }
    // now do the search
    try
    {
      for (i := 0; i < rows; i++)
      {
        for (j := 0; j < cols; j++)
        {
          echo ("now at ($i, $j) which is ${array[i][j]}")
          if (array[i][j] == 20) throw (Err("found it"))
        }
      }
    }
    catch (Err e)
    {
      echo (e.msg)
      return // and finish
    }
    echo ("No 20")
  }
}

Forth

include random.fs

10 constant X
10 constant Y

: ,randoms ( range n -- ) 0 do dup random 1+ , loop drop ;

create 2darray 20 X Y * ,randoms

: main
  Y 0 do
    cr
    X 0 do
      j X * i + cells 2darray + @
      dup .
      20 = if unloop unloop exit then
    loop
  loop ;

Fortran

Works with: Fortran version 77 and later

      PROGRAM LOOPNESTED
        INTEGER A, I, J, RNDINT

C       Build a two-dimensional twenty-by-twenty array.
        DIMENSION A(20,20)

C       It doesn't matter what number you put here.
        CALL SDRAND(123)

C       Fill the array with random numbers.
        DO 20 I = 1, 20
          DO 10 J = 1, 20
            A(I, J) = RNDINT(1, 20)
   10     CONTINUE
   20   CONTINUE

C       Print the numbers.
        DO 40 I = 1, 20
          DO 30 J = 1, 20
            WRITE (*,5000) I, J, A(I, J)

C           If this number is twenty, break out of both loops.
            IF (A(I, J) .EQ. 20) GOTO 50
   30     CONTINUE
   40   CONTINUE

C       If we had gone to 40, the DO loop would have continued. You can
C       label STOP instead of adding another CONTINUE, but it is good
C       form to only label CONTINUE statements as much as possible.
   50   CONTINUE
        STOP

C       Print the value so that it looks like one of those C arrays that
C       makes everybody so comfortable.
 5000   FORMAT('A[', I2, '][', I2, '] is ', I2)
      END

C FORTRAN 77 does not come with a random number generator, but it is
C easy enough to type "fortran 77 random number generator" into your
C preferred search engine and to copy and paste what you find. 
C The following code is a slightly-modified version of:
C
C     http://www.tat.physik.uni-tuebingen.de/
C         ~kley/lehre/ftn77/tutorial/subprograms.html
      SUBROUTINE SDRAND (IRSEED)
        COMMON  /SEED/ UTSEED, IRFRST
        UTSEED = IRSEED
        IRFRST = 0
        RETURN
      END
      INTEGER FUNCTION RNDINT (IFROM, ITO)
        INTEGER IFROM, ITO
        PARAMETER (MPLIER=16807, MODLUS=2147483647,                     &
     &              MOBYMP=127773, MOMDMP=2836)
        COMMON  /SEED/ UTSEED, IRFRST
        INTEGER HVLUE, LVLUE, TESTV, NEXTN
        SAVE    NEXTN
        IF (IRFRST .EQ. 0) THEN
          NEXTN = UTSEED
          IRFRST = 1
        ENDIF
        HVLUE = NEXTN / MOBYMP
        LVLUE = MOD(NEXTN, MOBYMP)
        TESTV = MPLIER*LVLUE - MOMDMP*HVLUE
        IF (TESTV .GT. 0) THEN
          NEXTN = TESTV
        ELSE
          NEXTN = TESTV + MODLUS
        ENDIF
        IF (NEXTN .GE. 0) THEN
          RNDINT = MOD(MOD(NEXTN, MODLUS), ITO - IFROM + 1) + IFROM
        ELSE
          RNDINT = MOD(MOD(NEXTN, MODLUS), ITO - IFROM + 1) + ITO + 1
        ENDIF
        RETURN
      END

Sample output:

A[ 1][ 1] is  2
A[ 1][ 2] is 16
A[ 1][ 3] is 16
A[ 1][ 4] is  3
A[ 1][ 5] is 16
A[ 1][ 6] is 15
A[ 1][ 7] is 18
A[ 1][ 8] is 14
A[ 1][ 9] is  9
A[ 1][10] is 10
A[ 1][11] is 12
A[ 1][12] is 15
A[ 1][13] is  3
A[ 1][14] is 19
A[ 1][15] is 20

Works with: Fortran version 90 and later

Here the special feature is that later Fortran allows loops to be labelled (with "outer" in this example) on their first and last statements. Any EXIT or CYCLE statements can then mention the appropriate label so as to be clear just which loop is involved, otherwise the assumption is the innermost loop only. And no "GO TO" statements need appear.

program Example
  implicit none

  real :: ra(5,10)
  integer :: ia(5,10)
  integer :: i, j

  call random_number(ra)
  ia = int(ra * 20.0) + 1

outer: do i = 1, size(ia, 1)
         do j = 1, size(ia, 2)
           write(*, "(i3)", advance="no") ia(i,j)
           if (ia(i,j) == 20) exit outer
         end do
         write(*,*)
       end do outer
       
end program Example

Sample output:

 14  2  1 11  8  1 14 11  3 15
  7 15 16  6  7 17  3 20 

FreeBASIC

' FB 1.05.0 Win64

Randomize
Dim a(1 To 20, 1 To 20) As Integer
For i As Integer = 1 To 20
  For j As Integer = 1 To 20
    a(i, j) = Int(Rnd * 20) + 1
  Next j
Next i

For i As Integer = 1 To 20
  For j As Integer = 1 To 20     
    Print Using "##"; a(i, j); 
    Print " ";
    If a(i, j) = 20 Then Exit For, For '' Exits both for loops
  Next j
  Print
Next i

Print
Print "Press any key to quit"
Sleep

Sample output :

Output:

13  3 16 13 16 11 15 19 10  5 12  7 17  1  6 11  2 19 11 11
12 17 20

Frink

array = new array[[10,10], {|x,y| random[1,20]}]

println["array is:\n" + formatTable[array, "right"] + "\n"]

[rows,cols] = array.dimensions[]

ROW:
for r = 0 to rows-1
   for c = 0 to cols-1
   {
      print[array@r@c + " " ]
      if array@r@c == 20
         break ROW
   }

Output:

array is:
19  1 15 14 10 20 13  4 20 14
12  2  4 16 17  4  1  8 20 18
12 17  2 11 13 14  9 18  4 16
15 14  1 13 16  9  8 10  3 12
14  1 14  5 17 20  5  6 15  3
17 10  6 16  1  2  4 14  2  6
14  7  1 13  7 16 10  3 11 11
 5  3 18 15 20 18 16  5 11  7
19 18  4  8  7 18 11 14  2  3
10 17 11 10 20 18 14 20 15 14

19 1 15 14 10 20 

FutureBasic

long a(9,9), i, j
BOOL done = NO

for i = 0 to 9
  for j = 0 to 9
    a(i,j) = rnd(20)
  next
next

for i = 0 to 9
  for j = 0 to 9
    print a(i,j)
    if ( a(i,j) == 20 ) then done = YES : break
  next
  if ( done ) then break
next

HandleEvents

Gambas

Click this link to run this code

Public Sub Main()
Dim siArray As New Short[5, 5]
Dim siCount0, siCount1 As Short
Dim bBreak As Boolean

For siCount0 = 0 To 4
  For siCount1 = 0 To 4
    siArray[siCount0, siCount1] = Rand(1, 20)
    siArray[siCount0, siCount1] = Rand(1, 20)
  Next
Next

For siCount0 = 0 To 4
  For siCount1 = 0 To 4
    If siArray[siCount0, siCount1] = 20 Then
      bBreak = True
      Break
    Endif
  Next
  If bBreak Then Break
Next

Print "Row " & Str(siCount0) & " column " & Str(siCount1) & " = 20"

End

Output:

Row 5 column 4 = 20

GAP

# You can't break an outer loop unless you return from the whole function.
n := 40;
a := List([1 .. n], i -> List([1 .. n], j -> Random(1, 20)));;

Find := function(a, x)
    local i, j, n;
    n := Length(a);
    for i in [1 .. n] do
        for j in [1 .. n] do
            if a[i][j] = x then
                return [i, j];
            fi;
        od;
    od;
    return fail;
end;

Find(a, 20);

Go

package main

import (
    "fmt"
    "math/rand"
    "time"
)

func main() {
    rand.Seed(time.Now().UnixNano())

    values := make([][]int, 10)
    for i := range values {
        values[i] = make([]int, 10)
        for j := range values[i] {
            values[i][j] = rand.Intn(20) + 1
        }
    }

outerLoop:
    for i, row := range values {
        fmt.Printf("%3d)", i)
        for _, value := range row {
            fmt.Printf(" %3d", value)
            if value == 20 {
                break outerLoop
            }
        }
        fmt.Printf("\n")
    }
    fmt.Printf("\n")
}

Groovy

Translation of: Java

Solution:

final random = new Random()
def a = []
(0..<10).each {
    def row = []
    (0..<10).each {
        row << (random.nextInt(20) + 1)
    }
    a << row
}

a.each { println it }
println ()

Outer:
for (i in (0..<a.size())) {
    for (j in (0..<a[i].size())) {
        if (a[i][j] == 20){
            println ([i:i, j:j])
            break Outer
        }
    }
}

Output:

[1, 19, 14, 16, 3, 12, 14, 18, 12, 6]
[6, 3, 8, 9, 17, 4, 10, 15, 17, 17]
[5, 12, 13, 1, 8, 18, 8, 15, 3, 20]
[8, 9, 6, 7, 2, 20, 17, 13, 6, 16]
[18, 6, 11, 13, 16, 20, 7, 3, 1, 14]
[6, 6, 19, 9, 9, 7, 16, 16, 3, 20]
[7, 6, 12, 7, 16, 14, 13, 18, 15, 15]
[19, 14, 14, 6, 4, 19, 5, 10, 13, 12]
[7, 6, 6, 12, 3, 9, 17, 12, 20, 7]
[10, 7, 15, 4, 17, 13, 14, 16, 8, 8]

[i:2, j:9]

Haskell

import Data.List
breakIncl :: (a -> Bool) -> [a] -> [a]
breakIncl p =  uncurry ((. take 1). (++)). break p

taskLLB k = map (breakIncl (==k)). breakIncl (k `elem`)

Example:

*Main> mapM_ (mapM_ print) $ taskLLB 20 [[2,6,17,5,14],[1,9,11,18,10],[13,20,8,7,4],[16,15,19,3,12]]
2
6
17
5
14
1
9
11
18
10
13
20

HicEst

REAL :: n=20, array(n,n)

array = NINT( RAN(10,10) )

DO row = 1, n
  DO col = 1, n
    WRITE(Name) row, col, array(row,col)
    IF( array(row, col) == 20 ) GOTO 99
  ENDDO
ENDDO

99 END

Icon and Unicon

Icon and Unicon use 'break' to exit loops and execute an expression argument. To exit nested loops 'break' is repeated as the expression.

procedure main()

every !(!(L  := list(10)) := list(10))  := ?20   # setup a 2d array of random numbers up to 20

every i := 1 to *L do                            # using nested loops
   every j := 1 to *L[i] do
      if L[i,j] = 20 then 
         break break write("L[",i,",",j,"]=20")

end

every x := L[i := 1 to *L,1 to *L[i]] do
    if x = 20 then break write("L[",i,",",j,"]=20")  # more succinctly  

every if !!L = 20 then break write("Found !!L=20")   # even more so (but looses the values of i and j

J

In J, using loops is usually a bad idea -- the underlying implementation implements a rich set of highly optimized special case loops. That said, general case loops can be used and can be a good choice when the operations provided by the primitives need to be severely pruned.

So, here's how the problem statement could be solved, without explicit loops (there's a conceptual nested loop and a short circuited search loop implemented within these primitives):

use=: ({.~ # <. 1+i.&20)@:,

Here's how the problem could be solved, using loops:

doubleLoop=: {{
  for_row. i.#y do.
    for_col. i.1{$y do.
      echo t=.(<row,col) { y
      if. 20=t do. return. end.
    end.
  end.
}}

Example use:

   use ?.20 20 $ 21
6 17 13 3 5 16 10 4 20
   doubleLoop ?.20 20 $ 21
6
17
13
3
5
16
10
4
20

The first approach is probably a couple thousand times faster than the second.

(In real life, good problem definitions might typically involve "use cases" (which are specified in terms of the problem domain, instead in terms of irrelevant details). Of course, "Rosetta Code" is about how concepts would be expressed in different languages. However, even here, tasks which dwell on language-specific issues are probably not a good use of people's time.)

Java

import java.util.Random;

public class NestedLoopTest {
    public static final Random gen = new Random();
    public static void main(String[] args) {
        int[][] a = new int[10][10];
        for (int i = 0; i < a.length; i++)
            for (int j = 0; j < a[i].length; j++)
                a[i][j] = gen.nextInt(20) + 1;

        Outer:for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[i].length; j++) {
                System.out.print(" " + a[i][j]);
                if (a[i][j] == 20)
                    break Outer; //adding a label breaks out of all loops up to and including the labelled loop
            }
            System.out.println();
        }
        System.out.println();
    }
}

JavaScript

Demonstrates use of break with a label. Uses print() function from Rhino.

// a "random" 2-D array 
var a = [[2, 12, 10, 4], [18, 11, 9, 3], [14, 15, 7, 17], [6, 19, 8, 13], [1, 20, 16, 5]];

outer_loop:
for (var i in a) {
    print("row " + i);
    for (var j in a[i]) {
        print(" " + a[i][j]);
        if (a[i][j] == 20) 
            break outer_loop;
    }
}
print("done");

In a functional idiom of JavaScript, however, we can not use a loop statement, as statements return no value and can not be composed within other functional expressions. Functional JavaScript often replaces a loop with a map or fold. In this case, we can achieve the same task by defining the standard list-processing function takeWhile, which terminates when a condition returns true.

We can then search the groups in the nested array by nesting takeWhile inside itself, and finally terminate when the 20 is found by one further application of takeWhile.

Using the same data as above, and returning the trail of numbers up to twenty from a nested and composable expression:

var lst = [[2, 12, 10, 4], [18, 11, 9, 3], [14, 15, 7, 17], [6, 19, 8, 13], [1,
  20, 16, 5]];

var takeWhile = function (lst, fnTest) {
    'use strict';
    var varHead = lst.length ? lst[0] : null;

    return varHead ? (
      fnTest(varHead) ? [varHead].concat(
        takeWhile(lst.slice(1), fnTest)
      ) : []
    ) : []
  },

  // The takeWhile function terminates when notTwenty(n) returns false
  notTwenty = function (n) {
    return n !== 20;
  },

  // Leftward groups containing no 20
  // takeWhile nested within takeWhile
  lstChecked = takeWhile(lst, function (group) {
    return takeWhile(
      group,
      notTwenty
    ).length === 4;
  });


// Return the trail of numbers preceding 20 from a composable expression

console.log(
  // Numbers before 20 in a group in which it was found
  lstChecked.concat(
    takeWhile(
      lst[lstChecked.length], notTwenty
    )
  )
  // flattened
  .reduce(function (a, x) {
    return a.concat(x);
  }).join('\n')
);

Output:

2
12
10
4
18
11
9
3
14
15
7
17
6
19
8
13
6
19
8
13
1

jq

jq has a `break` statement for breaking out of nested loops, and in this entry, it is used in the following function:

# Given an m x n matrix,
# produce a stream of the matrix elements (taken row-wise)
# up to but excluding the first occurrence of $max
def stream($max):
  . as $matrix
  | length as $m
  | (.[0] | length) as $n
  | label $ok
  | {i: range(0;$m), j: range(0;$n)}
  | $matrix[.i][.j] as $m
  | if $m == $max then break $ok else $m end ;

The nesting above could be made more visually explicit, for example, by using the equivalent form:

   range(0;$m) as $i
   | range(0;$n) as $j

but the previous formulation illustrates a concise alternative.

To generate the random matrix, and to accomplish the "pretty-printing" component of the task, the following function for converting a stream to an array of arrays is useful:

# Create an array of arrays by using the items in the stream, s,
# to create successive rows, each row having at most n items.
def reshape(s; n):
  reduce s as $s ({i:0, j:0, matrix: []};
    .matrix[.i][.j] = $s
    | if .j + 1 == n then .i += 1 | .j = 0 
      else .j += 1
      end)
  | .matrix;

Assuming the availability of rand/1 (e.g. as defined below), we can now readily define functions to create the matrix and pretty-print the items as required:

# Create an m x n matrix filled with numbers in [1 .. max]
def randomMatrix(m; n; max):
  reshape(limit(m * n; rand(max) + 1); n);

# Present the matrix up to but excluding the first occurrence of $max
def show($m; $n; $max):
  reshape( randomMatrix($m; $n; $max) | stream($max); $n)[] ;

# Main program for the problem at hand.
show(20; 4; 20)

Output:

Assuming proper placement of PRNG functions as defined below, the following invocation:

   $ jq -cn -f program.jq --arg seed 17 

produces:

[1,17,19,12]
[13,8,18,10]
[18,15,3,18]
[11,12,3,10]
[4,8,1,14]
[12,1,10,9]
[3,16,19,13]
[10,12,13]

PRNG

# LCG::Microsoft generates 15-bit integers using the same formula
# as rand() from the Microsoft C Runtime.
# Input: [ count, state, random ]
def next_rand_Microsoft:
  .[0] as $count
  | ((214013 * .[1]) + 2531011) % 2147483648 # mod 2^31
  | [$count+1 , ., (. / 65536 | floor) ];

def rand_Microsoft(seed):
  [0,seed]
  | next_rand_Microsoft  # the seed is not so random
  | recurse( next_rand_Microsoft )
  | .[2];

# A random integer in [0 ... (n-1)]:
# rand_Microsoft returns an integer in 0 .. 32767
def rand(n): n * (rand_Microsoft($seed|tonumber) / 32768) | trunc;

Jsish

/* Loops/Nested in Jsish */
Math.srand(0);
var nrows = Math.floor(Math.random() * 4) + 4;
var ncols = Math.floor(Math.random() * 6) + 6;

var matrix = new Array(nrows).fill(0).map(function(v, i, a):array { return new Array(ncols).fill(0); } );

var i,j;
for (i = 0; i < nrows; i++) for (j = 0; j < ncols; j++) matrix[i][j] = Math.floor(Math.random() * 20) + 1;

/* Labelled break point */
outer_loop:
for (i in matrix) {
    printf("row %d:", i);
    for (j in matrix[i]) {
        printf(" %d", matrix[i][j]);
        if (matrix[i][j] == 20) {
            printf("\n");
            break outer_loop;
        }
    }
    printf("\n");
}
puts(matrix);

/*
=!EXPECTSTART!=
row 0: 2 18 12 16 14 8 18 15 9 8
row 1: 15 6 8 16 17 12 15 2 10 3
row 2: 11 8 12 20
[ [ 2, 18, 12, 16, 14, 8, 18, 15, 9, 8 ],
  [ 15, 6, 8, 16, 17, 12, 15, 2, 10, 3 ],
  [ 11, 8, 12, 20, 18, 4, 6, 6, 19, 9 ],
  [ 16, 3, 2, 19, 1, 4, 8, 4, 11, 18 ] ]
=!EXPECTEND!=
*/

Output:

prompt$ jsish -u loopsNested.jsi
[PASS] loopsNested.jsi

Julia

M = [rand(1:20) for i in 1:5, j in 1:10]
R, C = size(M)

println("The full matrix is:")
println(M, "\n")

println("Find the first 20:")
for i in 1:R, j in 1:C
    n = M[i,j]
    @printf "%4d" n
    if n == 20
        println()
        break
    elseif j == C
        println()
    end
end

Output:

The full matrix is:
[9 17 10 8 6 10 13 12 7 12
 15 14 13 7 8 12 15 2 12 1
 8 3 4 14 19 1 3 13 11 15
 19 16 18 2 9 3 4 17 16 10
 16 4 20 19 8 1 18 14 12 4]

Find the first 20:
   9  17  10   8   6  10  13  12   7  12
  15  14  13   7   8  12  15   2  12   1
   8   3   4  14  19   1   3  13  11  15
  19  16  18   2   9   3   4  17  16  10
  16   4  20

Julia is column ordered, but this program searches in row order to be consistent with the other solutions of this task.

Kotlin

import kotlin.random.Random

fun main() {
    val a = Array(10) { IntArray(10) { Random.nextInt(1..20) } }
    println("array:")
    for (i in a.indices) println("row $i: ${a[i].contentToString()}")

    println("search:")
    outer@ for (i in a.indices) {
        print("row $i:")
        for (j in a[i].indices) {
            print(" " + a[i][j])
            if (a[i][j] == 20) break@outer
        }
        println()
    }
    println()
}

Output:

array:
row 0: [10, 8, 19, 17, 19, 7, 13, 16, 16, 4]
row 1: [6, 2, 6, 1, 11, 10, 2, 8, 1, 14]
row 2: [3, 6, 4, 6, 10, 2, 10, 20, 18, 1]
row 3: [16, 14, 6, 13, 18, 8, 18, 7, 4, 18]
row 4: [14, 10, 13, 11, 2, 17, 16, 19, 1, 1]
row 5: [4, 20, 6, 17, 20, 12, 20, 15, 16, 15]
row 6: [2, 20, 6, 5, 5, 15, 1, 2, 6, 18]
row 7: [14, 6, 8, 10, 12, 8, 12, 3, 14, 10]
row 8: [1, 5, 15, 12, 7, 14, 9, 7, 16, 11]
row 9: [20, 16, 5, 13, 15, 9, 3, 2, 2, 16]
search:
row 0: 10 8 19 17 19 7 13 16 16 4
row 1: 6 2 6 1 11 10 2 8 1 14
row 2: 3 6 4 6 10 2 10 20

Lambdatalk

1) the A.find function gets a value and a unidimensional array, 
   then retuns the item matching the value else -1  

{def A.find
 {def A.find.r
  {lambda {:val :arr :n :i :acc}
   {if {> :i :n}
    then -1
    else {if {= :val {A.get :i :arr}}
    then :i
    else {A.find.r :val :arr :n {+ :i 1} {A.addlast! :i :acc}}}}}}
 {lambda {:val :arr}
  {A.find.r :val :arr {- {A.length :arr} 1} 0 {A.new}}}}
-> A.find

{def A {A.new {S.serie 0 20}}}
-> A = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]

{A.find 12 {A}}
-> 12             // the index
{A.find 21 {A}}
-> -1             // not found

2) the AA.find function gets a value and a bidimensional array, 
   then returns the sequence of rows until the row containing the value, 
   and diplays the row containing the value if it exists else displays "the value was not found". 

{def AA.find
 {def AA.find.r
  {lambda {:val :arr :n :i}
   {if {> :i :n}
    then {br}:val was not found
    else {if {not {= {A.find :val {A.get :i :arr}} -1}}   // call the A.find function on each row
    then {br}:val was found in {A.get :i :arr} 
    else {br}{A.get :i :arr} {AA.find.r :val :arr :n {+ :i 1}} }}}}
 {lambda {:val :arr}
  {AA.find.r :val :arr {- {A.length :arr} 1} 0}}}
-> AA.find

3) testing

3.1) the rn function returns a random integer between 0 and n
{def rn {lambda {:n} {round {* :n {random}}}}}
-> rn

3.2) creating a bidimensional array containing random integers between 0 and 20
{def AA {A.new {A.new {rn 20} {rn 20} {rn 20} {rn 20} {rn 20}} 
               {A.new {rn 20} {rn 20} {rn 20} {rn 20} {rn 20}}
               {A.new {rn 20} {rn 20} {rn 20} {rn 20} {rn 20}}
               {A.new {rn 20} {rn 20} {rn 20} {rn 20} {rn 20}}}}
-> AA = [[9,4,10,14,1],[4,12,7,18,13],[7,13,19,12,11],[18,4,2,14,15]]

3.3) calling with a value which can be in the array
{AA.find 12 {AA}}
-> 
[9,4,10,14,1] 
12 was found in [4,12,7,18,13]

3.4) calling with a value outside of the array
{AA.find 21 {AA}} 
-> 
[9,4,10,14,1] 
[4,12,7,18,13] 
[7,13,19,12,11] 
[18,4,2,14,15] 
21 was not found

Lang

&values = fn.arrayMake(10)
$i
repeat($[i], 10) {
	&array = fn.arrayMake(10)
	
	$j
	repeat($[j], 10) {
		&array[$j] $= fn.randRange(20) + 1
	}
	
	&values[$i] ::= &array
}

$row
foreach($[row], &values) {
	$ele
	foreach($[ele], $row) {
		fn.print(\s$ele)
		
		if($ele === 20) {
			con.break(2) # Number of loops we want to break out of
		}
	}
	
	fn.println()
}

fn.println()

Output:

 18 17 9 3 14 7 6 4 13 18
 2 14 8 4 11 10 3 13 15 4
 19 17 3 10 4 15 13 6 16 9
 3 2 4 17 9 19 9 18 1 12
 2 18 13 20

Lasso

local(a) = array(
    array(2, 12, 10, 4), 
    array(18, 11, 9, 3), 
    array(14, 15, 7, 17), 
    array(6, 19, 8, 13), 
    array(1, 20, 16, 5)
)

// Query expression
with i in delve(#a) do {
    stdoutnl(#i)
    #i == 20 ? return
}

// Nested loops
#a->foreach => {
    #1->foreach => {
        stdoutnl(#1)
        #1 == 20 ? return
    }
}

Liberty BASIC

dim ar(10,10)
for i = 1 to 10
    for j = 1 to 10
        ar(i, j) = int(rnd(1) * 20) + 1
    next
next

flag=0
for x = 1 to 10
    for y = 1 to 10
        print ar(x,y)
        if ar(x,y) = 20 then
            flag=1
            exit for
        end if
    next
    if flag then exit for
next
print "Completed row ";x;" and column ";y

Lingo

-- create two-dimensional array with random numbers
a = []
repeat with i = 1 to 20
  a[i] = []
  repeat with j = 1 to 20
    a[i][j] = random(20)
  end repeat
end repeat

-- iterate over rows and columns, print value, exit both loops if it's 20
repeat with i = 1 to 20
  repeat with j = 1 to 20
    v = a[i][j]
    put v
    if v=20 then exit repeat
  end repeat
  if v=20 then exit repeat
end repeat

Lisaac

Section Header

+ name := TEST_LOOP_NESTED;

- external := `#include <time.h>`;

Section Public

- main <- (
  + a : ARRAY2[INTEGER];
  + i, j: INTEGER;

  `srand(time(NULL))`;
  a := ARRAY2[INTEGER].create(0, 0) to (9, 9);
  0.to 9 do { ii : INTEGER;
    0.to 9 do { jj : INTEGER;
      a.put (`rand()`:INTEGER % 20 + 1) to (ii, jj);
    };
  };
  { i < 10 }.while_do {
    j := 0;
    { j < 10 }.while_do {
      ' '.print;
      a.item(i, j).print;
      (a.item(i, j) = 20).if {
        i := 999;
        j := 999;
      };
      j := j + 1;
    };
    i := i + 1;
    '\n'.print;
  };
  '\n'.print;
);

LiveCode

repeat with i = 1 to 10
    repeat with j = 1 to 10
        put random(20) into aNums[i,j]
    end repeat
end repeat

repeat with i = 1 to 10
    repeat with j = 1 to 10
        if aNums[i,j] = 20 then 
            put true into exitLoop
            exit repeat
        end if
    end repeat
    if exitLoop then exit repeat
end repeat

if exitLoop then
    put "20 found in" && i & comma & j
else
    put "20 not found"
end if

Logo

make "a mdarray [10 10]

for [j 1 10] [for [i 1 10] [mdsetitem list :i :j :a (1 + random 20)]]

to until.20
  for [j 1 10] [
    for [i 1 10] [
      type mditem list :i :j :a
      type "| |
      if equal? 20 mditem list :i :j :a [stop]
    ]
    print "||
  ]
end
until.20

Lua

t = {}
for i = 1, 20 do 
  t[i] = {}
  for j = 1, 20 do t[i][j] = math.random(20) end
end
function exitable()
  for i = 1, 20 do
    for j = 1, 20 do
      if t[i][j] == 20 then 
        return i, j
      end
    end
  end
end
print(exitable())

M2000 Interpreter

We can use a number as a label, so instead of using "then goto there" we can use "then 1000" if label is 1000.

No numeric labels may have only comments in same line.

Numeric labels may have 1 to 5 digits, including leading zeros. So 00010 is label 10. Numeric labels have no : after, but if we place one then this isn't fault, because : is a statement separator.

In this example we execute nested for two times, using a third for.

Module Checkit {
            Dim A(10,10)<<Random(1, 20)
            For k=1 to 2 {
                  For i=0 to 9 {
                        For j=0 to 9 {
                              Print A(i,j)
                              if A(i,j)=20 then goto there
                        }
                  }
                  there:
                  Print "...ok", k
            }
}
Checkit

Maple

(m,n) := LinearAlgebra:-Dimensions(M):
for i from 1 to m do
  for j from 1 to n do
    print(M[i,j]);
    if M[i,j] = 20 then
      (i,j):=m,n; next;
    end if;
  end do;
end do:

Mathematica/Wolfram Language

Do[ Print[m[[i, j]]]; 
    If[m[[i, j]] === 20, Return[]], 
  {i, 1, Dimensions[m][[1]]}, 
  {j, 1, Dimensions[m][[2]]}]

MATLAB / Octave

Loops are considered slow in Matlab and Octave, it is preferable to vectorize the code.

	a = ceil(rand(100,100)*20);
	[ix,iy]=find(a==20,1)

A non-vectorized version of the code is shown below in Octave

Maxima

data: apply(matrix, makelist(makelist(random(100), 20), 20))$

find_value(a, x) := block(
   [p, q],
   [p, q]: matrix_size(a),
   catch(
      for i thru p do
         for j thru q do
            if a[i, j] = x then throw([i, j]),
      'not\ found
   )
)$

find_value(data, 100);
not found

MAXScript

fn scan_Nested arr =
(
	for subArray in arr where classof subArray == Array do
	(
		for item in subArray do
		(
			print item as string
			if item == 20 do return OK
		)
	)
)

Example:

testArray = #(#(1,5,2,19),#(11,20,7,2))
scan_nested testArray

#(#(1, 5, 2, 19), #(11, 20, 7, 2))
1
5
2
19
11
20
OK

Microsoft Small Basic

For row = 0 To 10
  For col = 0 To 10
    array[row][col] = Math.GetRandomNumber(20)
  EndFor
EndFor
For row = 0 To 10
  For col = 0 To 10
    TextWindow.WriteLine("row "+row+" col "+col+" value "+array[row][col])
    If array[row][col] = 20 Then
      Goto exit_for_row
    EndIf
  EndFor
EndFor
exit_for_row:

Output:

row 0 col 0 value 11
row 0 col 1 value 19
row 0 col 2 value 19
row 0 col 3 value 1
row 0 col 4 value 20

MOO

a = make(10, make(10));
for i in [1..10]
  for j in [1..10]
    a[i][j] = random(20);
  endfor
endfor
for i in [1..10]
  s = "";
  for j in [1..10]
    s += tostr(" ", a[i][j]);
    if (a[i][j] == 20)
      break i;
    endif
  endfor
  player:tell(s);
  s = "";
endfor
player:tell(s);

MUMPS

NESTLOOP
 ;.../loops/nested
 ;set up the 2D array with random values
 NEW A,I,J,K,FLAG,TRIGGER
 SET K=15 ;Magic - just to give us a size to work with
 SET TRIGGER=20 ;Magic - the max value, and the end value
 FOR I=1:1:K FOR J=1:1:K SET A(I,J)=$RANDOM(TRIGGER)+1
 ;Now, search through the array, halting when the value of TRIGGER is found
 SET FLAG=0
 SET (I,J)=0
 FOR I=1:1:K Q:FLAG  W ! FOR J=1:1:K WRITE A(I,J),$SELECT(J'=K:", ",1:"") SET FLAG=(A(I,J)=TRIGGER) Q:FLAG
 KILL A,I,J,K,FLAG,TRIGGER
 QUIT

Output:

USER>D NESTLOOP^ROSETTA
 
16, 4, 6, 20,
USER>D NESTLOOP^ROSETTA
 
9, 10, 10, 13, 2, 9, 6, 10, 1, 12, 12, 10, 8, 1, 13
7, 14, 12, 9, 14, 3, 20,

Neko

/**
 Loops/Nested in Neko
 Tectonics:
   nekoc loops-nested.neko
   neko loops-nested.neko
*/

var random = $loader.loadprim("std@random_new", 0)();
var random_int = $loader.loadprim("std@random_int", 2);

var values = $amake(10);
var row = 0;
var col = 0;

while row < 10 {
  values[row] = $amake(10);
  col = 0;
  while col < 10 {
    values[row][col] = random_int(random, 20) + 1;
    col += 1;
  }
  row += 1;
}

/* Look for a 20 */
/*
 To break out of nested loops, (without using labels and $goto),
   Neko needs the value of the inner loop(s).
 The break statement sets the return value of a loop expression.
 Without a break, the value of a loop expression is unspecified.
*/
var inner;
row = 0;
while row < 10 {
  col = 0;
  inner = while col < 10 {
    $print("values[", row, "][", col, "] = ", values[row][col], "\n");
    if values[row][col] == 20 break true;
    col += 1;
  }
  if $istrue(inner) break;
  row += 1;
}

Output:

prompt$ nekoc loops-nested.neko
prompt$ neko loops-nested       
values[0][0] = 17
values[0][1] = 1
values[0][2] = 8
values[0][3] = 5
values[0][4] = 18
values[0][5] = 17
values[0][6] = 17
values[0][7] = 19
values[0][8] = 2
values[0][9] = 1
values[1][0] = 11
values[1][1] = 4
values[1][2] = 16
values[1][3] = 11
values[1][4] = 12
values[1][5] = 20

Nemerle

Translation of: C#

Nemerle can jump out of a named block by invoking the blocks name with an optional return value.

using System;
using System.Console;
using Nemerle.Imperative;

module NestedLoops
{
    Main() : void
    {
        def arr = array(10, 10);
        def rnd = Random();
        
        foreach ((i, j) in $[(i, j) | i in [0 .. 9], j in [0 .. 9]])
            arr[i, j] = rnd.Next(1, 21);
            
        Finish:
        {
            foreach ((i, j) in $[(i, j) | i in [0 .. 9], j in [0 .. 9]])
            {
                Write("{0}  ", arr[i, j]);
                when (arr[i, j] == 20) Finish();
            }
        }
    }
}

NetRexx

/* NetRexx */
options replace format comments java crossref savelog symbols nobinary

  say
  say 'Loops/Nested'

  rnd = Random()
  dim2 = int[10, 10]

  -- build sample data
  loop i1 = 0 for dim2.length
    loop i2 = 0 for dim2[i1].length
      dim2[i1, i2] = rnd.nextInt(20) + 1
      end i2
    end i1

  -- run test
  loop x1 = 0 for dim2.length
    say Rexx(x1 + 1).right(4)': \-' 
    loop x2 = 0 for dim2[x1].length
      say Rexx(dim2[x1, x2]).right(3) || '\-'
      if dim2[x1, x2] = 20 then leave x1
      finally
        say
      end x2
    finally
      say
    end x1

I was somewhat disappointed by the performance of the above program and started a little performance analysis on solutions of this task for the languages I know.

I created a test program with a 500 x 500 matrix, all elements set to 0 except for the last one, which I set to 20. Then I repeat the search 100 times.

The timings are:

 Seconds elapsed
 3.978      NetRexx as above
 0.032      Netrex with option binary
 7.223      ooRexx with x[i,j]
 6.490      ooRexx with x.i.j
 0.188      PL/I Matrix as coded: FIXED 
 0.058      PL/I Matrix BIN FIXED(15)
14.217      the REXX program run with Regina
10.109      the REXX program run with ooRexx

NewLISP

(let (a (array 10 10))
  (dotimes (i 10)
    (dotimes (j 10)
      (setf (a i j) (rand 21))))
  (catch
      (dotimes (i 10)
	(dotimes (j 10)
	  (print (a i j))
	  (print " ")
	  (if (= 20 (a i j))
	      (throw))))))

Nim

import random, strutils

const ArrSize = 10

var a: array[ArrSize, array[ArrSize, int]]
var s = ""

randomize()   # Different results each time this runs.

# Initialize using loops on items rather than indexes.
for row in a.mitems:
  for item in row.mitems:
    item = rand(1..20)

block outer:
  # Loop using indexes.
  for i in 0..<ArrSize:
    for j in 0..<ArrSize:
      if a[i][j] < 10: s.add(' ')
      addf(s, "$#", $a[i][j])
      if a[i][j] == 20: break outer
      s.add(", ")
    s.add('\n')

echo s

Output:

 9, 16,  3, 18,  4, 17,  2, 16,  7,  6, 
 1,  6,  1, 11,  9,  8, 12,  7, 19,  8, 
13, 16,  4,  5,  2, 20

NS-HUBASIC

10 DIM A(20)
20 FOR I=1 TO 20
30 A(I)=RND(20)+1
40 NEXT
50 PRINT "THE FULL LIST:";
60 FOR I=1 TO 20
70 PRINT A(I);
80 NEXT
90 PRINT
100 PRINT "THE FULL LIST UP TO THE FIRST ";"INSTANCE OF 20:";
110 FOR I=1 TO 20
120 PRINT A(I);
130 IF A(I)=20 THEN END
140 NEXT

OCaml

In the interactive interpreter:

$ ocaml

# Random.self_init();;
- : unit = ()

# let m = Array.make_matrix 10 10 0 ;;
val m : int array array =
  [|[|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|];
    [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|];
    [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|];
    [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|];
    [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]|]

# for i = 0 to pred 10 do
    for j = 0 to pred 10 do
      m.(i).(j) <- 1 + Random.int 20
    done;
  done;;
- : unit = ()

# try
    for i = 0 to pred 10 do
      for j = 0 to pred 10 do
        Printf.printf " %d" m.(i).(j);
        if m.(i).(j) = 20 then raise Exit;
      done;
      print_newline()
    done;
  with Exit ->
    print_newline()
  ;;
 15 8 15 9 9 6 1 18 6 18
 17 1 13 15 13 1 16 4 13 9
 15 3 5 19 17 3 1 11 5 2
 1 1 6 19 20
- : unit = ()

Octave

Octave has no way of exiting nested loop; so we need a control variable, or we can use the trick of embedding the loops into a function and use the return statement. (The search for "exactly 20" is changed into a search for "almost 20")

function search_almost_twenty()
% create a 100x100 matrix...
m = unifrnd(0,20, 100,100);
for i = 1:100
  for j = 1:100
    disp( m(i,j) )
    if ( abs(m(i,j) - 20) < 1e-2 )
      return
    endif
  endfor
endfor
endfunction
    
search_almost_twenty()

% avoiding function, we need a control variable.
m = unifrnd(0,20, 100,100);
innerloopbreak = false;
for i = 1:100
  for j = 1:100
    disp( m(i,j) )
    if ( abs(m(i,j) - 20) < 1e-2 )
      innerloopbreak = true;
      break;
    endif
  endfor
  if ( innerloopbreak )
    break;
  endif
endfor

OoRexx

numbers = .array~new()
do i = 1 to 10
    do j = 1 to 10
        numbers[i,j] = random(1, 20)
    end
end

do i = 1 to numbers~dimension(1)
    do j = 1 to numbers~dimension(2)
        say numbers[i,j]
        if numbers[i,j] = 20 then
            leave i
    end
end

Oz

We can directly access and use the outer loop's break procedure:

declare
  fun {CreateMatrix Width Height}
    Matrix = {List.make Height}
  in
    for Row in Matrix do
       Row = {List.make Width}
       for X in Row do
          X = {OS.rand} mod 20 +1
       end
    end
    Matrix
  end

  proc {PrintMatrix Matrix}
    %% print until we see 20
     for Row in Matrix break:OuterBreak do
        for X in Row do
           {Show X}
           if X == 20 then {OuterBreak} end
        end
     end
  end
in
  {PrintMatrix {CreateMatrix 10 10}}

PARI/GP

M=matrix(10,10,i,j,random(20)+1);
for(i=1,10,for(j=1,10,if(M[i,j]==20,break(2))))

Pascal

Works with: FreePascal version 1.0

program LoopNested;
uses SysUtils;
const Ni=10; Nj=20;
var
  tab: array[1..Ni,1..Nj] of Integer;
  i, j: Integer;
label loopend;
begin
  for i := 1 to Ni do
    for j := 1 to Nj do
      tab[i,j]:=random(20)+1;
  for i := 1 to Ni do
  begin
    for j := 1 to Nj do
    begin
      WriteLn(tab[i,j]);
      if tab[i,j]=20 then goto loopend
    end
  end;
loopend:
end.

Perl

my $a = [ map [ map { int(rand(20)) + 1 } 1 .. 10 ], 1 .. 10];

Outer:
foreach (@$a) {
    foreach (@$_) {
        print " $_";
        if ($_ == 20) {
            last Outer;
        }
    }
    print "\n";
}
print "\n";

Phix

use an explicit flag

constant s = sq_rand(repeat(repeat(20,20),20))
integer found = 0
for i=1 to 20 do
    for j=1 to 20 do
        printf(1,"%d",s[i][j])
        if s[i][j]=20 then
            found = 1
            exit
        end if
        printf(1,", ")
    end for
    printf(1,"\n")
    if found then exit end if
end for

alternatively you can use a procedure

procedure till20()
    for i=1 to 20 do
        for j=1 to 20 do
            printf(1,"%d",s[i][j])
            if s[i][j]=20 then return end if
            printf(1,", ")
        end for
        printf(1,"\n")
    end for
end procedure
till20()
printf(1,"\n")

or a goto

procedure till20()
    for i=1 to 20 do
        for j=1 to 20 do
            printf(1,"%d",s[i][j])
            if s[i][j]=20 then goto :done end if
            printf(1,", ")
        end for
        printf(1,"\n")
    end for
  ::done
    printf(1,"\n")
end procedure
till20()

PHP

<?php
for ($i = 0; $i < 10; $i++)
    for ($j = 0; $j < 10; $j++)
        $a[$i][$j] = rand(1, 20);

foreach ($a as $row) {
    foreach ($row as $element) {
        echo " $element";
        if ($element == 20)
            break 2; // 2 is the number of loops we want to break out of
    }
    echo "\n";
}
echo "\n";
?>

PicoLisp

(for Lst (make (do 10 (link (make (do 10 (link (rand 1 20)))))))
   (T
      (for N Lst
         (printsp N)
         (T (= N 20) T) ) ) )

or:

(catch NIL
   (for Lst (make (do 10 (link (make (do 10 (link (rand 1 20)))))))
      (for N Lst
         (printsp N)
         (and (= N 20) (throw)) ) ) )

Pike

Pike does not have a generic goto, but break is a special case in that you can specify labels and break several levels of loop. In practise this is extremely seldom used in favor of using a state variable or containing the nest in a function that you return from in the inner loop. However it's there if you want it:

int main()
{
    // enumerate() normally returns a linearly enumerated array, but
    // allows for the forth argument to specify a function that will
    // be called and return the value that should be in each cell. We
    // create an anonymous function (lambda) that just returns a
    // random value.
    array a = ({});
    for(int i=0; i<20; i++)
        a += ({ enumerate( 20, 1, 1, lambda(){return random(20)+1;} ) });

    // We could use for() and a[x][y] indexing, but foreach is just
    // shorter and easier to use even if the 2D-array becomes less
    // obvious.
 mynestedloops:
    foreach(a, array inner_a) {
        foreach(inner_a, int value) {
            write(value +" ");
            if(value == 20)
                break mynestedloops;
        }
    }
    write("\n");
}

PL/I

   declare x(20,20) fixed;  /* 16 August 2010. */
   x = random()*20 + 1;
loops:
   do i = 1 to hbound(x,1);
      do j = 1 to hbound(x,2);
         put (x(i,j));
         if x(i,j) = 20 then leave loops;
      end;
      if x(i,j) = 20 then leave;
   end;

PureBasic

; Creating and filling array
Dim Value(10, 5)
For a = 0 To 10
  For b = 0 To 5
    Value(a, b) = Random(19) + 1
  Next
Next
; iterating trough array
For a = 0 To 10
  For b = 0 To 5
    Debug Value(a, b)
    If Value(a, b) = 20
      ; 2 indicates, that there are two nested lopps to break out
      Break 2
    EndIf
  Next
Next

Python

Python has only inner loop breaks. The normal way to solve this problem in Python is to move the code in a function, and use return:

from random import randint

def do_scan(mat):
    for row in mat:
        for item in row:
            print item,
            if item == 20:
                print
                return
        print
    print

mat = [[randint(1, 20) for x in xrange(10)] for y in xrange(10)]
do_scan(mat)

The , after print element suppresses printing a line break. The code needs some minor changes for Python 3.

Two more solutions around this problem, the first uses exception handling:

from random import randint

class Found20(Exception):
    pass

mat = [[randint(1, 20) for x in xrange(10)] for y in xrange(10)]

try:
    for row in mat:
        for item in row:
            print item,
            if item == 20:
                raise Found20
        print
except Found20:
    print

The second uses a flag variable:

from random import randint

mat = [[randint(1, 20) for x in xrange(10)] for y in xrange(10)]

found20 = False
for row in mat:
    for item in row:
        print item,
        if item == 20:
            found20 = True
            break
    print
    if found20:
        break

Qi

(define random-list
  0 -> []
  M -> [(1+ (RANDOM 20)) | (random-list (1- M))])

(define random-array
  0 _ -> []
  N M -> [(random-list M) | (random-array (1- N) M)])

(define array->list
  _    []                 -> []                                  \ "end outer loop" \
  Stop [[]          | Ra] -> (array->list Stop Ra)               \ "outer loop" \
  Stop [[Stop | _ ] | _ ] -> []                                  \ "break out from inner loop" \
  Stop [[X    | Rl] | Ra] -> [X | (array->list Stop [Rl | Ra])]) \ "inner loop" \

(array->list 20 (random-array 10 10))

Quackery

  [] 
  5 times
    [ []
      5 times [ 20 random 1+ join ]
      nested join ]
  
  dup say "Array contains:" cr
  witheach 
    [ witheach 
        [ echo sp ]
      cr ] 
  cr
  say "Array up to item = 20:" cr
  witheach
    [ false swap
      witheach
        [ dup 20 = iff
            [ drop not conclude ] 
          else 
            [ echo sp ] ] 
      iff conclude
      else cr ]

Output:

Array contains:
16 9 10 11 6 
2 10 14 12 20 
19 4 4 3 18 
15 20 10 7 3 
10 19 14 10 7 

Array up to item = 20:
16 9 10 11 6 
2 10 14 12 

R

m <- 10
n <- 10
mat <- matrix(sample(1:20L, m*n, replace=TRUE), nrow=m); mat
done <- FALSE
for(i in seq_len(m))
{
   for(j in seq_len(n))
   {
      cat(mat[i,j])
      if(mat[i,j] == 20)
      {
         done <- TRUE
         break
      } 
      cat(", ")     
   }
   if(done) 
   {
      cat("\n")
      break
   }
}

or

m <- 10; n <- 10; mat <- matrix(sample(1:20L, m*n, replace=TRUE), nrow=m);
x<-which(mat==20,arr.ind=TRUE,useNames=FALSE)
x<-x[order(x[,1]),]
for(i in mat[1:x[1,1]-1,]) print(i)
for(i in mat[x[1,1],1:x[1,2]]) print(i)

Racket

#lang racket
(define (scan xss)
  (for* ([xs xss]
         [x  xs]
         #:final (= x 20))
    (displayln x)))

(define matrix
  (for/list ([x 10])
    (for/list ([y 10])
      (+ (random 20) 1))))

(scan matrix)

Raku

(formerly Perl 6)

Works with: rakudo version 2015-09-18

my @a = [ (1..20).roll(10) ] xx *;

LINE: for @a -> @line {
    for @line -> $elem {
        print " $elem";
        last LINE if $elem == 20;
    }
    print "\n";
}
print "\n";

Output:

 15 6 14 13 14 7 9 16 8 18
 7 6 18 11 19 13 12 5 18 8
 17 17 9 5 4 8 17 8 3 11
 9 20

REBOL

REBOL [
	Title: "Loop/Nested"
	URL: http://rosettacode.org/wiki/Loop/Nested
]

; Number formatting.
zeropad: func [pad n][
    n: to-string n  insert/dup n "0" (pad - length? n)  n]

; Initialize random number generator from current time.
random/seed now 

; Create array and fill with random numbers, range 1..20.
soup: array [10 10]
repeat row soup [forall row [row/1: random 20]]

print "Loop break using state variable:"
done: no
for y 1 10 1 [
	for x 1 10 1 [
		prin rejoin [zeropad 2 soup/:x/:y  " "]
		if 20 = soup/:x/:y [done: yes  break]
	]
	prin crlf
	if done [break]
]

print [crlf "Loop break with catch/throw:"]
catch [
	for y 1 10 1 [
		for x 1 10 1 [
			prin rejoin [zeropad 2 soup/:x/:y  " "]
			if 20 = soup/:x/:y [throw 'done]
		]
		prin crlf
	]
]
prin crlf

Output:

Loop break using state variable:
15 09 11 03 17 07 09 16 03 07
03 15 04 06 13 05 10 06 02 14
17 05 06 12 03 19 03 03 17 04
17 15 14 17 15 07 06 16 13 11
02 08 12 16 04 14 03 19 02 02
02 13 14 14 15 01 10 07 17 03
07 17 20

Loop break with catch/throw:
15 09 11 03 17 07 09 16 03 07
03 15 04 06 13 05 10 06 02 14
17 05 06 12 03 19 03 03 17 04
17 15 14 17 15 07 06 16 13 11
02 08 12 16 04 14 03 19 02 02
02 13 14 14 15 01 10 07 17 03
07 17 20

ReScript

let m = []

for _ in 0 to 9 {
  let n = []
  for _ in 0 to 9 {
    let _ = Js.Array2.push(n, 1 + Js.Math.random_int(0, 20))
  }
  let _ = Js.Array2.push(m, n)
}

try {
  for i in 0 to 9 {
    for j in 0 to 9 {
      Js.log(m[i][j])
      if m[i][j] == 20 { raise(Exit) }
    }
  }
} catch {
| Exit => Js.log("stop")
}

REXX

Since the two-dimensional array could potentially not be large enough to contain the target (20), it's possible to not find the target.
Code was added to this REXX program to reflect that possibility and issue an appropriate message (whether the target was found or not).

/*REXX program loops through a two-dimensional array to search for a  '20'    (twenty). */
parse arg rows cols targ .                       /*obtain optional arguments from the CL*/
if rows=='' | rows==","  then rows=60            /*Rows not specified?  Then use default*/
if cols=='' | cols==","  then cols=10            /*Cols  "      "         "   "     "   */
if targ=='' | targ==","  then targ=20            /*Targ  "      "         "   "     "   */
w=max(length(rows), length(cols), length(targ))  /*W:  used for formatting the output.  */
not= 'not'                                       /* [↓]  construct the 2─dimension array*/
          do     row=1  for rows                 /*ROW  is the 1st dimension of array.  */
              do col=1  for cols                 /*COL   "  "  2nd     "      "   "     */
              @.row.col=random(1, targ)          /*create some positive random integers.*/
              end   /*row*/
          end       /*col*/

          do     r=1  for rows    /* ◄───────────────── now, search for the target {20}.*/
              do c=1  for cols
              say left('@.'r"."c, 3+w+w) '=' right(@.r.c, w)    /*show an array element.*/
              if @.r.c==targ  then do; not=; leave r; end       /*found the targ number?*/
              end   /*c*/
          end       /*r*/

say right( space( 'Target'  not  "found:" )    targ, 33, '─')
                                                 /*stick a fork in it,  we're all done. */

output   when using the default inputs:

@.1.1   = 19
@.1.2   = 14
@.1.3   = 16
@.1.4   =  8
@.1.5   =  1
@.1.6   =  4
@.1.7   = 11
@.1.8   =  7
@.1.9   = 15
@.1.10  = 16
@.2.1   = 11
@.2.2   =  4
@.2.3   =  3
@.2.4   =  6
@.2.5   = 18
@.2.6   =  7
@.2.7   =  5
@.2.8   =  7
@.2.9   =  2
@.2.10  =  7
@.3.1   = 20
─────────────────Found target: 20

output   when using the input of:   2   2

@.1.1   = 14
@.1.2   =  6
@.2.1   = 13
@.2.2   = 13
─────────────Target not found: 20

Ring

size = 5
array = newlist(size,size)
for row = 1 to size
    for col = 1 to size
        array[row][col] = random(19) + 1
    next
next

for row = 1 to size
    for col = 1 to size
        see "row " + row + " col " + col + "value : " + array[row][col] + nl
        if array[row][col] = 20 exit for row ok
    next
next 

func newlist x, y
     if isstring(x) x=0+x ok
     if isstring(y) y=0+y ok
     aList = list(x)
     for t in aList
         t = list(y)
     next
     return aList

Output:

row 1 col 1 value : 10
row 1 col 2 value : 3
row 1 col 3 value : 8
row 1 col 4 value : 8
row 1 col 5 value : 1
row 2 col 1 value : 3
row 2 col 2 value : 3
row 2 col 3 value : 4
row 2 col 4 value : 6
row 2 col 5 value : 8
row 3 col 1 value : 14
row 3 col 2 value : 12
row 3 col 3 value : 2
row 3 col 4 value : 11
row 3 col 5 value : 9
row 4 col 1 value : 17
row 4 col 2 value : 9
row 4 col 3 value : 19
row 4 col 4 value : 12
row 4 col 5 value : 12
row 5 col 1 value : 7
row 5 col 2 value : 6
row 5 col 3 value : 17
row 5 col 4 value : 5
row 5 col 5 value : 6

RPL

As there is no BREAK instruction in RPL, premature loop exit is usually made by forcing the loop variable to its end value. Depending on the way exit is required and on the need for code optimization within the loop, there are several ways to implement such a break feature. The following one is based on two FOR..NEXT loops:

≪
  { 10 10 } 0 CON
  1 10 FOR j
    1 10 FOR k
       j k 2 →LIST RAND 20 * CEIL PUT
    NEXT
  NEXT
  DROP 1 CF
  1 10 FOR j
    1 10 FOR k
      DUP j k 2 →LIST GET
      DUP 1 DISP
      IF 20 == THEN 1 SF END
    1 FC? 1 10 IFTE STEP
  1 FC? 1 10 IFTE STEP 
≫

We could also only use a WHILE..REPEAT loop, scanning the matrix line by line, but there is no nested loop anymore:

≪ 46 → done
  ≪ { 10 10 } 0 CON
     { 1 1 }
     DO 
        RAND 20 * CEIL PUTI 
     UNTIL done FS? END 
     DO 
        GETI DUP 1 DISP
     UNTIL 20 == done FS? OR END  
≫ ≫

The done constant is the number of the system flag that becomes set when the last element of the matrix is written. The above value is for HP-28 versions; HP-48 users must change it to -64.

Ruby

As the break command only jumps out of the innermost loop, this task requires Ruby's catch/throw functionality.

ary = (1..20).to_a.shuffle.each_slice(4).to_a
p ary

catch :found_it do
  for row in ary
    for element in row
      print "%2d " % element
      throw :found_it if element == 20
    end
    puts ","
  end
end

puts "done"

Output:

[[2, 12, 10, 4], [18, 11, 9, 3], [14, 15, 7, 17], [6, 19, 8, 13], [1, 20, 16, 5]]
 2 12 10  4 ,
18 11  9  3 ,
14 15  7 17 ,
 6 19  8 13 ,
 1 20 done

However, for-loops are not very popular. This is more idiomatic ruby, which avoids loops and breaking out of them:

p slices = [*1..20].shuffle.each_slice(4)

slices.any? do |slice|
  puts
  slice.any? do |element|
    print "#{element} "
    element == 20
  end
end
puts "done"

Output:

#<Enumerator: [1, 4, 9, 13, 15, 10, 3, 5, 14, 17, 18, 8, 2, 12, 6, 19, 20, 11, 7, 16]:each_slice(4)>

1 4 9 13 
15 10 3 5 
14 17 18 8 
2 12 6 19 
20 done

Run BASIC

dim a(10,10)
cls
for row = 1 TO 10
        for col = 1 TO 10
                a(row,col) = INT(20 * RND(1) + 1)
        next col
next row
 
for row = 1 to 10
        for col = 1 to 10
               print a(row, col)
                if a(row, col) = 20 then goto [end]
        next col
next row
[end]
print "At row:";row;" col:";col

Rust

Library: rand

use rand::Rng;

extern crate rand;

fn main() {
    let mut matrix = [[0u8; 10]; 10];
    let mut rng = rand::thread_rng();

    for row in matrix.iter_mut() {
        for item in row.iter_mut() {
            *item = rng.gen_range(0, 21);
        }
    }

    'outer: for row in matrix.iter() {
        for &item in row.iter() {
            print!("{:2} ", item);
            if item == 20 { break 'outer }
        }
        println!();
    }
}

Output:

 5  3  8 18 13  2  5 13  6 17
 5 14 20

Sather

class MAIN is
  main is
    a:ARRAY2{INT} := #(10,10);
    i, j :INT;
    
    RND::seed(1230);
    loop i := 0.upto!(9);
      loop j := 0.upto!(9);
         a[i, j] := RND::int(1, 20);
      end;
    end;

    loopthis ::= true;
    loop i := 0.upto!(9); while!( loopthis );
      loop j := 0.upto!(9);
        #OUT  + " " + a[i, j];
        if a[i, j] = 20 then
	  loopthis := false;
	  break!;
	end;
      end;
    end;
  end;
end;

S-BASIC

S-BASIC doesn't have a BREAK or EXIT statement for early termination of a loop, so the most straight-forward approach is to jump out using a GOTO. But since S-BASIC doesn't allow GOTOs from a FOR..NEXT loop, we have to use WHILE..DO instead.

$constant ROWS = 10
$constant COLUMNS = 10
$constant MAXVAL = 20

var i, j = integer
dim integer table(ROWS, COLUMNS)

rem - populate table using nested FOR..NEXT loops

for i=1 to ROWS 
  for j=1 to COLUMNS 
     table(i, j) = int(rnd(1) * MAXVAL) + 1
  next j
next i

rem - show results using nested WHILE..DO loops

i = 1
while i <= ROWS do
  begin
    j = 1
    while j <= COLUMNS do
      begin
        print using "## "; table(i, j);
        if table(i, j) = MAXVAL then goto 0done
        j = j + 1
      end
    print
    i = i + 1
  end

comment
  Although S-BASIC allows alphanumeric line numbers as the target
  of a GOTO or GOSUB statement, the first "digit" must in fact be  
  a number, as shown here.
end

0done if i > ROWS then print "target value"; MAXVAL; " not found!"

end

The use of GOTO, while convenient, is at odds with S-BASIC's structured programming ethos. Adding a boolean flag to the inner loop allows us to avoid the GOTO. Although S-BASIC has no explicit boolean variable type, integers, real numbers, characters, and strings can all be used as boolean variables. For integers, 0 is false and -1 is true. For real variables, 0 is false and any non-zero value is true. For characters, 'T', 't', 'Y', and 'y' are evaluated as true, while 'F', 'f', 'N', and 'n' are evaluated as false. Strings follow the same rule, with only the first character considered.

$constant ROWS = 10
$constant COLUMNS = 10
$constant TOPVAL = 20
$constant TRUE = FFFFH
$constant FALSE = 0H

var i, j, done = integer
dim integer table(ROWS, COLUMNS)

rem - populate table using nested FOR..NEXT loops

for i=1 to ROWS 
  for j=1 to COLUMNS 
     table(i, j) = int(rnd(1) * TOPVAL) + 1
  next j
next i

rem - show results using nested WHILE..DO loops

i = 1
done = FALSE
while i <= ROWS and not done do
  begin
    j = 1
    while j <= COLUMNS and not done do
      begin
        print using "## "; table(i, j);
        if table(i, j) = TOPVAL then done = TRUE
        j = j + 1
      end
    print
    i = i + 1
  end

if i > ROWS then print "Target value of"; TOPVAL; " not found!"

end

Output:

The output is the same for both programs.

 1  2  7 20

Scala

In Scala there is no build-in 'break' keyword. That functionality comes from a library.

import scala.util.control.Breaks._
val a=Array.fill(5,4)(scala.util.Random.nextInt(21))
println(a map (_.mkString("[", ", ", "]")) mkString "\n")
breakable {
  for(row <- a; x <- row){
    println(x)
    if (x==20) break
  }
}

Output:

[14, 16, 5, 7]
[0, 15, 13, 20]
[0, 3, 8, 17]
[4, 20, 2, 2]
[12, 6, 11, 15]
14
16
5
7
0
15
13
20

Scheme

Using call/cc:

(call-with-current-continuation
 (lambda (return)
   (for-each (lambda (a)
	       (for-each (lambda (b)
			   (cond ((= 20 b)
				  (newline)
				  (return))
				 (else
				  (display " ")(display b))))
			 a)
	       (newline))
	     array)))

Using tail-call:

(let loop ((a array))
  (if (pair? a)
      (let loop2 ((b (car a)))
	(cond ((null? b)
	       (newline)
	       (loop (cdr a)))
	      ((= 20 (car b))
	       (newline))
	      (else
	       (display " ")(display (car b))
	       (loop2 (cdr b)))))))

Scilab

Works with: Scilab version 5.5.1

ni=3;nj=4
t=int(rand(ni,nj)*20)+1
for i=1:ni
    for j=1:nj
        printf("%2d ",t(i,j))
        if t(i,j)==11 then break; end
    end
    printf("\n")
    if t(i,j)==11 then break; end
end

Output:

 5 18 19  8 
 5 14  5  6 
 5  7  7 12 

Seed7

$ include "seed7_05.s7i";

const proc: main is func
  local
    var integer: i is 0;
    var integer: j is 0;
    var array array integer: a is 10 times 10 times 0;
    const EXCEPTION: FOUND20 is enumlit;
  begin
    for i range 1 to 10 do
      for j range 1 to 10 do
        a[i][j] := rand(1, 20);
      end for;
    end for;
    block
      for i range 1 to 10 do
        for j range 1 to 10 do
          write(a[i][j] lpad 2 <& ", ");
          if a[i][j] = 20 then
            raise FOUND20;
          end if;
        end for;
        writeln;
      end for;
    exception
      catch FOUND20: writeln;
    end block;
  end func;

Output:

15, 10,  5,  9, 10, 13,  1,  9, 11, 10, 
 5,  6, 10, 13,  4, 13, 11, 12,  2,  4, 
 4, 16, 20, 

Sidef

var arr = 10.of{ 10.of{ 20.irand + 1 } }

for row in arr {
    for num in row {
        "%3d".printf(num);
        num == 20 && goto :OUT
    }
    print "\n"
} @:OUT

print "\n"

Output:

  9 17 14 17 17  7  1  3  9 18
  1 12  1 19  9  5  1 17 19  3
 17  2 18 12 15 10  8 13 13 14
 12 16 13 13  2 11  3 15  2  4
 15 15  8 11  5  2  1 16  8 13
 17  3  1  1  8 12  4 20

Smalltalk

Notice that the original answer (see below) was wrong (never say never say never...).

Works with: Smalltalk/X

it looks a bit wierd, but here is: loopWithExit

|i|

i := 1.
[:exit |
    Transcript showCR:i.
    i == 5 ifTrue:[ exit value:'stopped' ].
    i := i + 1.
] loopWithExit

these can also be nested, and exited from the inner loop:

|i|

i := 1.
[:exit1 |
    |j|

    j := 0.
    [:exit2 |
        Transcript showCR:('i is %1 / j is %2' bindWith:i with:j).
        j == 5 ifTrue:[ exit2 value: nil ].
        i == 5 ifTrue:[ exit1 value: nil ].
        j := j + 1.
    ] loopWithExit.
    i := i + 1
] loopWithExit

in case your smalltalk does not have it, here's the definition:

!Block methodsFor:'looping'!
loopWithExit
    "the receiver must be a block of one argument.  It is evaluated in a loop forever, 
     and is passed a block, which, if sent a value:-message, will exit the receiver block, 
     returning the parameter of the value:-message. Used for loops with exit in the middle."

    |exitBlock|

    exitBlock := [:exitValue | ^ exitValue].
    [true] whileTrue:[ self value:exitBlock ]

in the same spirit, exits could be added to many other loop constructs. However, this is really only very rarely needed in Smalltalk, because a ^(return) out of a block returns from the enclosing method which usually used to exit early from search utility methods.

There is also valueWithExit, which can be used to get out of a block early and provide an alternative value. Using that, the tasks solution is:

|v result|

v := 1 to:20 collect:[:i |
        1 to:20 collect:[:j | Random nextIntegerBetween:1 and:20 ]
     ].

result := 
    [:exit |
        1 to:20 do:[:row |
            1 to:20 do:[:col |
                |element|

                (element := (v at:row) at:col) printCR.
                element == 20 ifTrue:[ exit value:(row @ col) ].
            ]
        ].
        nil
    ] valueWithExit.

result isNil ifTrue:[
    'ouch - no 20 found' printCR.
] ifFalse:[
    '20 found at ' print. result printCR
]

Output:

19
6
1
7
12
20
20 found at 1@6

Works with: GNU Smalltalk

Smalltalk has no ways of escaping from loops (single or nested), even if it is possible to extend its iteration capabilities in several ways.

The following code implements a BiArray class with a method that allows iteration over the elements (by columns and then by rows) and execution of a block if a condition is true.

"this simple implementation of a bidimensional array
 lacks controls over the indexes, but has a way of iterating
 over array's elements, from left to right and top to bottom"
Object subclass: BiArray [
  |cols rows elements|
  BiArray class >> columns: columns  rows: howManyRows [ 
      ^ super basicNew init: columns per: howManyRows
  ]
  init: columns per: howManyRows [
     cols := columns.
     rows := howManyRows.
     elements := Array new: ( columns * howManyRows )
  ]
  calcIndex: biIndex [ "column, row (x,y) to linear"
    ^ ( (biIndex at: 1) + (((biIndex at: 2) - 1) * cols) )
  ]
  at: biIndex [ "biIndex is an indexable containing column row"
     ^ elements at: (self calcIndex: biIndex).
  ]
  directAt: i [ ^ elements at: i ]
  at: biIndex put: anObject [
     elements at: (self calcIndex: biIndex) put: anObject
  ]
  whileTrue: aBlock do: anotherBlock [
     |i lim|
     i := 1. lim := rows * cols.
     [ ( i <= lim )
         & (aBlock value: (self directAt: i) )
     ] whileTrue: [ 
         anotherBlock value: (self directAt: i).
         i := i + 1.
       ]
  ]
].

|biarr|
biarr := BiArray columns: 10 rows: 10.

"fill the array; this illustrates nested loop but not how to
 escape from them"
1 to: 10 do: [ :c |
  1 to: 10 do: [ :r |
     biarr at: {c . r} put: (Random between: 1 and: 20)
  ]
].

"loop searching for 20; each block gets the element passed as argument"
biarr whileTrue: [ :v | v ~= 20 ] 
      do: [ :v | v displayNl ]

SPL

'fill array
mx,my = 30
> y, 1..my
  > x, 1..mx
    a[x,y] = #.rnd(20)+1
  <
<
'scan array
> y, 1..my
  > x, 1..mx
    #.output("x=",x,", y=",y, ", a=",a[x,y])
    << a[x,y] = 20
  <
  << x!>mx
<

Output:

x=1, y=1, a=7
x=2, y=1, a=7
x=3, y=1, a=19
x=4, y=1, a=1
x=5, y=1, a=20

Stata

In Stata macro language, one can only break the innermost loop, with continue, break. There are several ways to cope with this.

First, build the matrix:

matrix a=J(20,20,0)
forv i=1/20 {
	forv j=1/20 {
		matrix a[`i',`j']=runiformint(1,20)
	}
}

Use nested forvalues. If 20 is found, set a flag and break the inner loop. In the outer loop, check the flag and break the outer loop if 20 was found.

local q 0
forv i=1/20 {
	forv j=1/20 {
		display "check `i',`j'"
		if el("a",`i',`j')==20 {
			display "found at `i',`j'"
			local q 1
			continue, break
		}
	}
	
	if `q' continue, break
}
if !`q' {
	display "not found"
}

Use nested while loops, and check both the loop indices and a flag. One could also use an inner forvalue loop together with an outer while loop.

local q 0
local i=1
while !`q' & `i'<=20 {
	local j=1
	while !`q' & `j'<=20 {
		display "check `i',`j'"
		if el("a",`i',`j')==20 {
			display "found at `i',`j'"
			local q 1
		}
		local ++j
	}
	local ++i
}
if !`q' {
	display "not found"
}

Use the exit/capture exception mechanism: exit tos throw an exception, and capture to catch it. Since this catches all exception, you have then to check the value of _rc.

capture {
	forv i=1/20 {
		forv j=1/20 {
			display "check `i',`j'"
			if el("a",`i',`j')==20 {
				display "found at `i',`j'"
				exit -1
			}
		}
	}
}
if _rc==-1 {
	// value was found
}
else if _rc==0 {
	display "not found"
}
else exit _rc

Mata

In Mata, the situation is simpler: one may return from a program without resort to exceptions, or use the goto statement. It's still possible to use break and flags though.

function findval1(a,x,i0,j0) {
	n=rows(a)
	p=cols(a)
	for (i=1; i<=n; i++) {
		for (j=1; j<=p; j++) {
			if (a[i,j]==x) {
				i0=i
				j0=j
				return(1)
			}
		}
	}
	return(0)
}

function findval2(a,x,i0,j0) {
	n=rows(a)
	p=cols(a)
	q=0
	for (i=1; i<=n; i++) {
		for (j=1; j<=p; j++) {
			if (a[i,j]==x) {
				i0=i
				j0=j
				q=1
				goto END
			}
		}
	}
END:
	return(q)
}

function findval3(a,x,i0,j0) {
	n=rows(a)
	p=cols(a)
	q=0
	for (i=1; i<=n; i++) {
		for (j=1; j<=p; j++) {
			if (a[i,j]==x) {
				i0=i
				j0=j
				q=1
				break
			}
		}
		if (q) {
			break
		}
	}
	return(q)
}

Then with any of these functions, the return value indicates whether x has been found in a, and i,j are the indices where it has been found.

a=st_matrix("a")
findval1(a,20,i=.,j=.)
findval2(a,20,i=.,j=.)
findval3(a,20,i=.,j=.)

Swift

let array = [[2, 12, 10, 4], [18, 11, 20, 2]]

loop: for row in array {
    for element in row {
        println(" \(element)")
        if element == 20 { break loop }
    }
}
print("done")

Output:

 2
 12
 10
 4
 18
 11
 20
done

Tailspin

In Tailspin you break processing by simply not sending a value on in the chain.

sink find20
  def a: $;
  1 -> #
  when <..$a::length> do def i: $;
    '$#10;' -> !OUT::write
    1 -> \(
      when <$a($i)::length~..> do $i + 1 !
      otherwise def j: $;
        def val: $a($i;$j);
        ' $val;' -> !OUT::write
        $val -> \(<~=20> $j + 1 ! \) -> #
    \) -> #
end find20

[1..10 -> [1..10 -> 20 -> SYS::randomInt -> $ + 1]] -> !find20

Output:

 3 4 2 10 10 10 2 16 9 14
 10 2 8 7 19 13 9 9 2 6
 5 8 11 18 14 5 3 1 7 19
 18 18 16 3 1 19 19 8 6 6
 18 9 17 16 13 16 12 15 4 2
 12 20

Tcl

Tcl only supports single-level breaks; exiting more deeply nested looping requires the use of exceptions, which are considerably more verbose before Tcl 8.6.

Works with: Tcl version 8.6

set ary [subst [lrepeat 10 [lrepeat 5 {[expr int(rand()*20+1)]}]]]

try {
    foreach row $ary {
        foreach col $row {
            puts -nonewline [format %3s $col]
            if {$col == 20} {
                throw MULTIBREAK "we're done"
            }
        }
        puts ,
    }
} trap MULTIBREAK {} {}
puts " done"

Output:

 12 13 14 13 15,
  1 14  7 16  3,
 12 11  5  1  9,
 12  5  1  4  2,
  6 11 11  4 11,
  7 14 20 done

TI-83 BASIC

PROGRAM:LOOP
(A,B)→dim([C])
For(I,1,A)
For(J,1,B)
int(rand*20+1)→[C](I,J)
End
End
For(I,1,A)
For(J,1,B)
Disp [C](I,J)
If [C](I,J)=20
Then
Stop
End
End
End

3→A:4→B:prgmLOOP

TI-89 BASIC

The Stop statement exits the containing program.

Prgm
  Local mat,i,j
  © randMat(5, 5) exists but returns -9 to 9 rather than 1 to 20
  newMat(5, 5) → mat
  For i,1,rowDim(mat)
    For j,1,colDim(mat)
      rand(20) → mat[i,j]
    EndFor
  EndFor
  Disp mat
  Pause "Press a key."
  ClrIO
  For i,1,rowDim(mat)
    For j,1,colDim(mat)
      If mat[i,j] = 20 Then
        Stop
      Else
        Output i*8, j*18, mat[i,j]
      EndIf
    EndFor
  EndFor
EndPrgm

TUSCRIPT

$$ MODE TUSCRIPT
LOOP
row=""
 LOOP/CLEAR x=1,10
 x=RANDOM_NUMBERS (1,20,1)
 row=APPEND(row," ",x)
  IF (x==20) THEN
   PRINT row
   EXIT,EXIT
  ENDIF
 ENDLOOP
 PRINT row
ENDLOOP

Output:

9 6 6 5 10 18 11 17 17 9
5 16 2 4 2 15 13 13 4 9
12 4 6 19 3 1 3 12 13 8
3 7 4 8 15 12 1 20 

UNIX Shell

Works with: Bash

Bash doesn't have two-dimentional arrays, so we fake it for this example

size=10

for ((i=0;i<size;i++)); do
  unset t[@]
  for ((j=0;j<size;j++)); do
    t[$j]=$((RANDOM%20+1))
  done
  a[$i]="${t[*]}"
done

for ((i=0;i<size;i++)); do
  t=(${a[$i]})
  for ((j=0;j<size;j++)); do
    printf "%2d " ${t[$j]}
    [ ${t[$j]} -eq 20 ] && break 2
  done
  echo
done
echo

Example output:

 7  5  4  6  4  5  2 15 10  7 
15  4 14  9 10 14 14  3  3  5 
14 20 

Vala

void main() {
  
  int[,] a = new int[10, 10];
  bool broken = false;
  for (int i = 0; i < 10; i++)
    for (int j = 0; j < 10; j++)
      a[i, j] = Random.int_range(0, 21) % 20 + 1;

  for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
      stdout.printf(" %d", a[i, j]);
      if (a[i, j] == 20) {
        broken = true;
        break;
      }
    }
    stdout.printf("\n");
    if (broken) break;
  }
}

VBA

Public Sub LoopsNested()
    Dim a(1 To 10, 1 To 10) As Integer
    Randomize
    For i = 1 To 10
        For j = 1 To 10
            a(i, j) = Int(20 * Rnd) + 1
        Next j
    Next i
    For i = 1 To 10
        For j = 1 To 10
            If a(i, j) <> 20 Then
                Debug.Print a(i, j),
            Else
                i = 10 'Upperbound iterator outerloop
                Exit For 'Exit For exits only innerloop
            End If
        Next j
        Debug.Print
    Next i
End Sub

Visual Basic .NET

VB.NET doesn't have labelled loops, but the Exit statement discriminates between different types of block, allowing for several workarounds other than using a goto.

The set-up code:

Module Program
    Sub Main()
        Const ROWS = 10
        Const COLS = 10

        ' Initialize with seed 0 to get deterministic output (may vary across .NET versions, though).
        Dim rand As New Random(0)

        ' VB uses max index array declarations
        Dim nums(ROWS - 1, COLS - 1) As Integer

        For r = 0 To ROWS - 1
            For c = 0 To COLS - 1
                nums(r, c) = rand.Next(0, 21) ' Upper bound is exclusive.
            Next
        Next

        ' MISSING IMPLEMENTATION
    End Sub
End Module

Implementations:

Perhaps the simplest solution is to use a goto.

        For r = 0 To ROWS - 1
            For c = 0 To COLS - 1
                Dim val = nums(r, c)
                Console.WriteLine(val)
                If val = 20 Then GoTo BREAK
            Next
        Next
        BREAK:

If, for some reason, a goto is undesirable, an alternative would be to exit a dummy outer block (in this case a single-iteration Do loop).

        Do
            For r = 0 To ROWS - 1
                For c = 0 To COLS - 1
                    Dim val = nums(r, c)
                    Console.WriteLine(val)
                    If val = 20 Then Exit Do
                Next
            Next
        Loop While False

Either For loop can also be converted to a different type of loop.

        For r = 0 To ROWS - 1
            Dim c = 0
            Do While c <= COLS - 1
                Dim val = nums(r, c)
                Console.WriteLine(val)
                If val = 20 Then Exit For
                c += 1
            Loop
        Next

The search can also be factored out to a separate method

    Sub Find20Impl(arr As Integer(,))
        For r = 0 To arr.GetLength(0) - 1
            For c = 0 To arr.GetLength(1) - 1
                Dim val = arr(r, c)
                Console.WriteLine(val)
                If val = 20 Then Exit Sub
               'If val = 20 Then Return ' Equivalent to above.
            Next
        Next
    End Sub

and called from Main():

        Find20Impl(nums)

A translation of the VBA above, that sets the iteration variable of the outer For loop to an out-of-range value and exits the inner loop regularly.

        For r = 0 To ROWS - 1
            For c = 0 To COLS - 1
                Dim val = nums(r, c)
                Console.WriteLine(val)
                If val = 20 Then
                    r = ROWS
                    Exit For
                End If
            Next
        Next

Similarly, a flag variable can be checked by the outer loop.

        Dim done = False
        For r = 0 To ROWS - 1
            For c = 0 To COLS - 1
                Dim val = nums(r, c)
                Console.WriteLine(val)
                If val = 20 Then
                    done = True
                    Exit For
                End If
            Next
            If done Then Exit For
        Next

Output:

15
17
16
11
4
11
19
9
20

V (Vlang)

import rand
import rand.seed

fn main() {
    rand.seed(seed.time_seed_array(2))
    
    mut values := [][]int{len:10, init: []int{len:10}}
    for i in 0..values.len{
        for j in 0..values[0].len {
            values[i][j] = rand.intn(20) or {19} +1
        }
    }
outerloop:
    for i,row in values {
        println('${i:3})')
        for value in row {
            print(' ${value:3}')
            if value==20{
                break outerloop
            }
        }
        println('')
    }
}

Wren

Library: Wren-fmt

Wren doesn't have goto or break label so to break out of nested loops you need to use a flag (found in the code below).

import "random" for Random
import "./fmt" for Fmt

var rand = Random.new()

var a = List.filled(20, null)
for (i in 0..19) {
    a[i] = List.filled(20, 0)
    for (j in 0..19) a[i][j] = rand.int(1, 21)
}

var found = false
for (i in 0..19) {
    for (j in 0..19) {
        Fmt.write("$4d", a[i][j])
        if (a[i][j] == 20) {
            found = true
            break
        }
    }
    System.print()
    if (found) break
}

Output:

Sample run:

   8   5   4   9   5   7  13   8   8  13  17  10   9   4   8  14  16   5   5   9
  11  18  16   9   6  17  14   5  10  13  15   8   2   6  18  20

XBasic

Works with: Windows XBasic

Break out of nested loops by means of an additional variable.

PROGRAM "loopsnested"

IMPORT "xst" ' for XstGetSystemTime

DECLARE FUNCTION Entry()

' Pseudo-random number generator
' Based on the rand, srand functions from Kernighan & Ritchie's book
' 'The C Programming Language'
DECLARE FUNCTION Rand()
DECLARE FUNCTION SRand(seed%%)

FUNCTION Entry()
  DIM array%[10, 10]
  XstGetSystemTime (@msec)
  SRand(INT(msec) MOD 32768)
  FOR row% = 0 TO 10
    FOR col% = 0 TO 10
      array%[row%, col%] = INT(Rand() / 32768.0 * 20.0) + 1
    NEXT col%
  NEXT row%

  isFound% = $$FALSE
  FOR row% = 0 TO 10
    PRINT "Row:"; row%
    FOR col% = 0 TO 10
      PRINT " Col:"; col%; ", value:"; array%[row%, col%]
      IF array%[row%, col%] = 20 THEN
        isFound% = $$TRUE
        EXIT FOR
      END IF
    NEXT col%
    IFT isFound% THEN
      EXIT FOR
    END IF
  NEXT row%
END FUNCTION

' Return pseudo-random integer on 0..32767
FUNCTION Rand()
  #next&& = #next&& * 1103515245 + 12345
END FUNCTION USHORT(#next&& / 65536) MOD 32768

' Set seed for Rand()
FUNCTION SRand(seed%%)
  #next&& = seed%%
END FUNCTION

END PROGRAM

Output:

Row: 0
 Col: 0, value: 1
 Col: 1, value: 6
 Col: 2, value: 15
 Col: 3, value: 19
 Col: 4, value: 6
 Col: 5, value: 7
 Col: 6, value: 19
 Col: 7, value: 8
 Col: 8, value: 11
 Col: 9, value: 9
 Col: 10, value: 15
Row: 1
 Col: 0, value: 3
 Col: 1, value: 7
 Col: 2, value: 18
 Col: 3, value: 1
 Col: 4, value: 7
 Col: 5, value: 8
 Col: 6, value: 9
 Col: 7, value: 14
 Col: 8, value: 4
 Col: 9, value: 20

XPL0

include c:\cxpl\codes;                  \intrinsic 'code' declarations
def  Size=10;

proc Nest(A);   \Display 2-dimensional array A contents until 20 is found
int  A;
int  I, J, K;
[for J:= 0 to Size-1 do
    for I:= 0 to Size-1 do
        [K:= A(I,J);
        IntOut(0, K);  ChOut(0, ^ );
        if K = 20 then return;          \there is no 'goto' instruction
        ];
]; \Nest

proc Fill(A);   \Fill 2-dimensional array A with random numbers 1..20
int  A;
int  I, J;
[for J:= 0 to Size-1 do
    for I:= 0 to Size-1 do
        A(I,J):= Ran(20)+1;
]; \Fill

int Array(Size,Size);
[Fill(Array);
 Nest(Array);
]

zkl

Using nested lists to simulate a 5x5 array. No breakbreak so an exception is used to long jump out of the loop (just 'cause, a state var could also be used).

const N=5;
var rows=(0).pump(N,List, (0).pump.fp(N,List,(1).random.fpM("1-",21)) );
try{
   foreach r in (N){
      foreach c in (N){ 
         x:=rows[r][c]; x.print(",");
         if (x==20) { println("Found it!"); throw(Exception.Generic); }
      }
   }
   println("Not found");
}catch(Generic){}

Output:

14,13,17,11,11,3,15,20,Found it!
3,2,10,14,10,2,2,15,2,13,11,5,12,4,17,8,10,5,14,11,10,14,11,4,1,Not found

ZX Spectrum Basic

10 DIM a(10,10)
20 FOR i=1 TO 10: FOR j=1 TO 10
30 LET a(i,j)=INT (RND*20)+1
40 NEXT j: NEXT i
50 LET b=0: REM flag to abort loops
60 FOR i=1 TO 10: FOR j=1 TO 10
70 PRINT (" " AND a(i,j)<10);a(i,j);" ";
80 IF a(i,j)=20 THEN LET i=10: LET j=10: LET b=1: REM abort loops
90 NEXT j
100 IF b=0 THEN PRINT
110 NEXT i
120 STOP

Example output:

16  7  8  6 14  8 12 14 12  9
 7  9 14  8 18 17  3 16  1 19
 5 13  7 11 13 14  4  7 19 14
20