For in COBOL

COBOL provides several ways to implement loops. Here are some basic types of loops in COBOL.

IDENTIFICATION DIVISION.
PROGRAM-ID. FOR-LOOPS.

DATA DIVISION.
WORKING-STORAGE SECTION.
01 I PIC 9(2) VALUE 1.
01 J PIC 9(2) VALUE 0.
01 N PIC 9(2) VALUE 0.

PROCEDURE DIVISION.
MAIN-PROCEDURE.
    *> The most basic type, with a single condition.
    PERFORM UNTIL I > 3
        DISPLAY I
        ADD 1 TO I
    END-PERFORM

    *> A classic initial/condition/after loop.
    PERFORM VARYING J FROM 0 BY 1 UNTIL J >= 3
        DISPLAY J
    END-PERFORM

    *> Another way of accomplishing the basic "do this N times" iteration.
    PERFORM 3 TIMES
        DISPLAY "range" FUNCTION WHEN-COMPILED(7:2)
    END-PERFORM

    *> PERFORM without a condition will loop indefinitely until EXIT PERFORM.
    PERFORM FOREVER
        DISPLAY "loop"
        EXIT PERFORM
    END-PERFORM

    *> You can also use CONTINUE to skip to the next iteration of the loop.
    PERFORM VARYING N FROM 0 BY 1 UNTIL N >= 6
        IF FUNCTION MOD(N, 2) = 0
            CONTINUE
        ELSE
            DISPLAY N
        END-IF
    END-PERFORM

    STOP RUN.

When you run this COBOL program, it will produce the following output:

1
2
3
0
1
2
range 01
range 01
range 01
loop
1
3
5

In COBOL, we use different constructs to achieve looping:

PERFORM UNTIL is used for condition-based loops.
PERFORM VARYING is used for counter-based loops, similar to the classic for loop in other languages.
PERFORM n TIMES is used to execute a block of code a specific number of times.
PERFORM FOREVER creates an infinite loop that can be exited using EXIT PERFORM.
CONTINUE can be used to skip to the next iteration of a loop.

COBOL doesn’t have a direct equivalent to Go’s range keyword for iterating over sequences, so we’ve simulated it using PERFORM n TIMES. The FUNCTION WHEN-COMPILED is used here just to generate some varying output for each iteration.

COBOL’s looping constructs are powerful and flexible, allowing for various types of iteration and control flow within loops.

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For in COBOL