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   1  package integer;
   2  
   3  our $VERSION = '1.00';
   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;