integer - phpMan

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

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