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1 | package integer; |
2 | |
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3 | =head1 NAME |
4 | |
5 | integer - Perl pragma to compute arithmetic in integer instead of double |
6 | |
7 | =head1 SYNOPSIS |
8 | |
9 | use integer; |
10 | $x = 10/3; |
11 | # $x is now 3, not 3.33333333333333333 |
12 | |
13 | =head1 DESCRIPTION |
14 | |
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15 | This tells the compiler to use integer operations |
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16 | from here to the end of the enclosing BLOCK. On many machines, |
17 | this doesn't matter a great deal for most computations, but on those |
18 | without floating point hardware, it can make a big difference. |
19 | |
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20 | Note that this affects the operations, not the numbers. If you run this |
21 | code |
22 | |
23 | use integer; |
24 | $x = 1.5; |
25 | $y = $x + 1; |
26 | $z = -1.5; |
27 | |
28 | you'll be left with C<$x == 1.5>, C<$y == 2> and C<$z == -1>. The $z |
29 | case happens because unary C<-> counts as an operation. |
30 | |
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31 | Native integer arithmetic (as provided by your C compiler) is used. |
32 | This means that Perl's own semantics for arithmetic operations may |
33 | not be preserved. One common source of trouble is the modulus of |
34 | negative numbers, which Perl does one way, but your hardware may do |
35 | another. |
36 | |
37 | % perl -le 'print (4 % -3)' |
38 | -2 |
39 | % perl -Minteger -le 'print (4 % -3)' |
40 | 1 |
41 | |
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42 | See L<perlmod/Pragmatic Modules>. |
43 | |
44 | =cut |
45 | |
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46 | sub import { |
47 | $^H |= 1; |
48 | } |
49 | |
50 | sub unimport { |
51 | $^H &= ~1; |
52 | } |
53 | |
54 | 1; |