MirOS Manual: integer(3p)


integer(3p)     Perl Programmers Reference Guide      integer(3p)

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 frac-
     tional 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);

perl v5.8.8                2005-02-05                           1

integer(3p)     Perl Programmers Reference Guide      integer(3p)

     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

perl v5.8.8                2005-02-05                           2

Generated on 2014-04-02 20:57:59 by $MirOS: src/scripts/roff2htm,v 1.79 2014/02/10 00:36:11 tg Exp $

These manual pages and other documentation are copyrighted by their respective writers; their source is available at our CVSweb, AnonCVS, and other mirrors. The rest is Copyright © 2002‒2014 The MirOS Project, Germany.
This product includes material provided by Thorsten Glaser.

This manual page’s HTML representation is supposed to be valid XHTML/1.1; if not, please send a bug report – diffs preferred.