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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;

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