Even Odd in Algol68

Welcome to the Even Odd in Algol68 page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

MODE PARSEINT_RESULT = STRUCT(BOOL valid, INT value, STRING leftover);

PROC parse int = (REF STRING s) PARSEINT_RESULT:
(
    BOOL valid := FALSE;
    REAL r := 0.0;
    INT n := 0;
    STRING leftover;

    # Associate string with a file #
    FILE f;
    associate(f, s);

    # On end of input, exit if valid number not seen. Otherwise ignore it #
    on logical file end(f, (REF FILE dummy) BOOL:
        (
            IF NOT valid THEN done FI;
            TRUE
        )
    );

    # Exit if value error #
    on value error(f, (REF FILE dummy) BOOL: done);

    # Convert string to real number #
    get(f, r);

    # If real number is in range of an integer, convert to integer. Indicate integer is valid if same as real #
    IF ABS r <= max int
    THEN
        n := ENTIER(r);
        valid := (n = r)
    FI;

    # Get leftover string #
    get(f, leftover);

done:
    close(f);
    PARSEINT_RESULT(valid, n, leftover)
);

PROC usage = VOID: printf(($gl$, "Usage: please input a number"));

# Parse 1st command-line argument #
STRING s := argv(4);
PARSEINT_RESULT result := parse int(s);

# If invalid or extra characters, exit #
INT n := value OF result;
IF NOT (valid OF result) OR (leftover OF result) /= ""
THEN
    usage;
    stop
FI;

printf(($gl$, (n MOD 2 = 0 | "Even" | "Odd")))

Even Odd in Algol68 was written by:

• rzuckerm

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

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How to Run the Solution

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