prompt = proc (s: string) returns (int)
    stream$puts(stream$primary_output(), s)
    return(int$parse(stream$getl(stream$primary_input())))
end prompt

start_up = proc ()
    po: stream := stream$primary_output()

    % Ask for width and height
    width: int := prompt("Width? ")
    height: int := prompt("Height? ")

    % Create an array of arrays.
    % In order to actually create separate arrays, rather than repeating
    % a reference to the same array over and over, fill_copy must be used.
    arr: array[array[int]] :=
        array[array[int]]$fill_copy(1, width, array[int]$fill(1, height, 0))

    % Set a value
    x: int := 1+width/2
    y: int := 1+height/2
    arr[x][y] := 123

    % Retrieve the value
    stream$putl(po, "arr[" || int$unparse(x) || "][" || int$unparse(y)
                 || "] = " || int$unparse(arr[x][y]))

    % The array will be automatically garbage-collected once there
    % are no more references to it.
end start_up