phpman > man > integer(3perl)

NAME
    integer - Perl pragma to use integer arithmetic instead of floating point

SYNOPSIS
        use integer;
        $x = 10/3;
        # $x is now 3, not 3.33333333333333333

DESCRIPTION
    This tells the compiler to use integer operations from here to the end of the enclosing BLOCK.
    On many machines, this doesn't matter a great deal for most computations, but on those without
    floating point hardware, it can make a big difference in performance.

    Note that this only affects how most of the arithmetic and relational operators handle their
    operands and results, and not how all numbers everywhere are treated. Specifically, "use
    integer;" has the effect that before computing the results of the arithmetic operators (+, -, *,
    /, %, +=, -=, *=, /=, %=, and unary minus), the comparison operators (<, <=, >, >=, ==, !=,
    <=>), and the bitwise operators (|, &, ^, <<, >>, |=, &=, ^=, <<=, >>=), the operands have their
    fractional portions truncated (or floored), and the result will have its fractional portion
    truncated as well. In addition, the range of operands and results is restricted to that of
    familiar two's complement integers, i.e., -(2**31) .. (2**31-1) on 32-bit architectures, and
    -(2**63) .. (2**63-1) on 64-bit architectures. For example, this code

        use integer;
        $x = 5.8;
        $y = 2.5;
        $z = 2.7;
        $a = 2**31 - 1;  # Largest positive integer on 32-bit machines
        $, = ", ";
        print $x, -$x, $x+$y, $x-$y, $x/$y, $x*$y, $y==$z, $a, $a+1;

    will print: 5.8, -5, 7, 3, 2, 10, 1, 2147483647, -2147483648

    Note that $x is still printed as having its true non-integer value of 5.8 since it wasn't
    operated on. And note too the wrap-around from the largest positive integer to the largest
    negative one. Also, arguments passed to functions and the values returned by them are not
    affected by "use integer;". E.g.,

        srand(1.5);
        $, = ", ";
        print sin(.5), cos(.5), atan2(1,2), sqrt(2), rand(10);

    will give the same result with or without "use integer;" The power operator "**" is also not
    affected, so that 2 ** .5 is always the square root of 2. Now, it so happens that the pre- and
    post- increment and decrement operators, ++ and --, are not affected by "use integer;" either.
    Some may rightly consider this to be a bug -- but at least it's a long-standing one.

    Finally, "use integer;" also has an additional affect on the bitwise operators. Normally, the
    operands and results are treated as unsigned integers, but with "use integer;" the operands and
    results are signed. This means, among other things, that ~0 is -1, and -2 & -5 is -6.

    Internally, native integer arithmetic (as provided by your C compiler) is used. This means that
    Perl's own semantics for arithmetic operations may not be preserved. One common source of
    trouble is the modulus of negative numbers, which Perl does one way, but your hardware may do
    another.

        % perl -le 'print (4 % -3)'
        -2
        % perl -Minteger -le 'print (4 % -3)'
        1

    See "Pragmatic Modules" in perlmodlib, "Integer Arithmetic" in perlop