Prime Number in ALGOL 60

Welcome to the Prime Number in ALGOL 60 page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

begin
    procedure usage;
    begin
        outstring(1, "Usage: please input a non-negative integer\n");
        stop
    end usage;

    comment Input a digit character from stdin and return the following:
        - "0" to "9" maps to 0 to 9
        - "+" maps to 10
        - "-" maps to 11
        - comma maps to 12
        - whitespace maps to 13
        - null byte maps to -1
        - invalid bytes map to -2;
    integer procedure indigit;
    begin
        comment Mapping:
            - "0" to "9" maps to 1 to 10
            - "+" maps to 11
            - "-" maps to 12
            - "," maps to 13
            - "\t" maps to 14
            - "\r" maps to 15
            - "\n" maps to 16
            - " " maps to 17
            - null byte maps to 18
            - invalid byte maps 0;
        integer ch;
        inchar(0, "0123456789+-,\t\r\n ", ch);
        if ch < 1 then ch := -2
        else if ch < 14 then ch := ch - 1
        else if ch < 18 then ch := 13
        else ch := -1;
        indigit := ch
    end indigit;

    procedure ignoreWhitespace(ch);
    integer ch;
    begin
    whiteloop:
        if ch = 13 then
        begin
            ch := indigit;
            goto whiteloop
        end
    end ignoreWhitespace;

    comment Input an integer from stdin into 'result' and parse it.
        The last character is read into 'ch'.
        return true if integer is valid, false otherwise;
    boolean procedure inValidInteger(result, ch);
    integer result, ch;
    begin
        boolean valid;
        integer s;

        result := 0;
        valid := false;
        s := 1;

        comment Ignore whitespace;
        ch := indigit;
        ignoreWhitespace(ch);

        comment Process signs: ignore "+" and invert sign if "-";
    signloop:
        if ch = 10 | ch = 11 then
        begin
            if ch = 11 then s := -s;
            ch := indigit;
            goto signloop
        end;

        comment Process digits: update value;
    valueloop:
        if ch >= 0 & ch <= 9 then
        begin
            comment Invalid if overflow or underflow;
            valid := true;
            if (s > 0 & (maxint - ch) % 10 < result) |
                (s < 0 & (-1 - maxint + ch) % 10 > result) then valid := false
            else result := result * 10 + s * ch;

            ch := indigit;
            goto valueloop
        end;

        comment Ignore whitespace;
        ignoreWhitespace(ch);

        inValidInteger := valid
    end inValidInteger;

    integer procedure mod(x, n);
    value x, n;
    integer x, n;
    begin
        mod := x - n * (x % n)
    end mod;

    boolean procedure isprime(x);
    value x;
    integer x;
    begin
        boolean result;
        integer i, q;

        result := x = 2 | (x > 2 & mod(x, 2) != 0);
        if result then
        begin
            q := entier(sqrt(x));
            for i := 3, i + 2 while result & i <= q do
            begin
                result := mod(x, i) != 0
            end
        end;

        isprime := result
    end isprime;

    integer argc, result, ch;

    comment Get number of parameters. Exit if too few;
    ininteger(0, argc);
    if argc < 1 then usage;

    comment Get integer value from 1st argument. Exit if invalid, not
        end of argument, or negative;
    if !inValidInteger(result, ch) | ch != -1 | result < 0 then usage;

    comment Output "prime" if number is prime, "composite" otherwise;
    if isprime(result) then outstring(1, "prime")
    else outstring(1, "composite")
end

Prime Number in ALGOL 60 was written by:

• rzuckerm

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

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

No 'How to Run the Solution' section available. Please consider contributing.