function ModuloInteger takes integer dividend, integer divisor returns integer
    local integer modulus = dividend - (dividend / divisor) * divisor

    // If the dividend was negative, the above modulus calculation will
    // be negative, but within (-divisor..0).  We can add (divisor) to
    // shift this result into the desired range of (0..divisor).
    if (modulus < 0) then
        set modulus = modulus + divisor
    endif

    return modulus
endfunction

5 - (5 / 2) * 2 = ?

5 / 2 = 2
2 * 2 = 4
5 - 4 = 1