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    1 package integer;
    2 
    3 our $VERSION = '1.01';
    4 
    5 =head1 NAME
    6 
    7 integer - Perl pragma to use integer arithmetic instead of floating point
    8 
    9 =head1 SYNOPSIS
   10 
   11     use integer;
   12     $x = 10/3;
   13     # $x is now 3, not 3.33333333333333333
   14 
   15 =head1 DESCRIPTION
   16 
   17 This tells the compiler to use integer operations from here to the end
   18 of the enclosing BLOCK.  On many machines, this doesn't matter a great
   19 deal for most computations, but on those without floating point
   20 hardware, it can make a big difference in performance.
   21 
   22 Note that this only affects how most of the arithmetic and relational
   23 B<operators> handle their operands and results, and B<not> how all
   24 numbers everywhere are treated.  Specifically, C<use integer;> has the
   25 effect that before computing the results of the arithmetic operators
   26 (+, -, *, /, %, +=, -=, *=, /=, %=, and unary minus), the comparison
   27 operators (<, <=, >, >=, ==, !=, <=>), and the bitwise operators (|, &,
   28 ^, <<, >>, |=, &=, ^=, <<=, >>=), the operands have their fractional
   29 portions truncated (or floored), and the result will have its
   30 fractional portion truncated as well.  In addition, the range of
   31 operands and results is restricted to that of familiar two's complement
   32 integers, i.e., -(2**31) .. (2**31-1) on 32-bit architectures, and
   33 -(2**63) .. (2**63-1) on 64-bit architectures.  For example, this code
   34 
   35     use integer;
   36     $x = 5.8;
   37     $y = 2.5;
   38     $z = 2.7;
   39     $a = 2**31 - 1;  # Largest positive integer on 32-bit machines
   40     $, = ", ";
   41     print $x, -$x, $x+$y, $x-$y, $x/$y, $x*$y, $y==$z, $a, $a+1;
   42 
   43 will print:  5.8, -5, 7, 3, 2, 10, 1, 2147483647, -2147483648
   44 
   45 Note that $x is still printed as having its true non-integer value of
   46 5.8 since it wasn't operated on.  And note too the wrap-around from the
   47 largest positive integer to the largest negative one.   Also, arguments
   48 passed to functions and the values returned by them are B<not> affected
   49 by C<use integer;>.  E.g.,
   50 
   51     srand(1.5);
   52     $, = ", ";
   53     print sin(.5), cos(.5), atan2(1,2), sqrt(2), rand(10);
   54 
   55 will give the same result with or without C<use integer;>  The power
   56 operator C<**> is also not affected, so that 2 ** .5 is always the
   57 square root of 2.  Now, it so happens that the pre- and post- increment
   58 and decrement operators, ++ and --, are not affected by C<use integer;>
   59 either.  Some may rightly consider this to be a bug -- but at least it's
   60 a long-standing one.
   61 
   62 Finally, C<use integer;> also has an additional affect on the bitwise
   63 operators.  Normally, the operands and results are treated as
   64 B<unsigned> integers, but with C<use integer;> the operands and results
   65 are B<signed>.  This means, among other things, that ~0 is -1, and -2 &
   66 -5 is -6.
   67 
   68 Internally, native integer arithmetic (as provided by your C compiler)
   69 is used.  This means that Perl's own semantics for arithmetic
   70 operations may not be preserved.  One common source of trouble is the
   71 modulus of negative numbers, which Perl does one way, but your hardware
   72 may do another.
   73 
   74     % perl -le 'print (4 % -3)'
   75     -2
   76     % perl -Minteger -le 'print (4 % -3)'
   77     1
   78 
   79 See L<perlmodlib/"Pragmatic Modules">, L<perlop/"Integer Arithmetic">
   80 
   81 =cut
   82 
   83 $integer::hint_bits = 0x1;
   84 
   85 sub import {
   86     $^H |= $integer::hint_bits;
   87 }
   88 
   89 sub unimport {
   90     $^H &= ~$integer::hint_bits;
   91 }
   92 
   93 1;