- $x = 1.5;
- $y = $x + 1;
- $z = -1.5;
-
-you'll be left with C<$x == 1.5>, C<$y == 2> and C<$z == -1>. The $z
-case happens because unary C<-> counts as an operation.
-
-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 L<perlmod/Pragmatic Modules>.
+ $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 B<not> affected
+by C<use integer;>. E.g.,
+
+ srand(1.5);
+ $, = ", ";
+ print sin(.5), cos(.5), atan2(1,2), sqrt(2), rand(10);
+
+will give the same result with or without C<use integer;> The power
+operator C<**> 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 C<use integer;>
+either. Some may rightly consider this to be a bug -- but at least it's
+a long-standing one.
+
+Finally, C<use integer;> also has an additional affect on the bitwise
+operators. Normally, the operands and results are treated as
+B<unsigned> integers, but with C<use integer;> the operands and results
+are B<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 L<perlmodlib/"Pragmatic Modules">, L<perlop/"Integer Arithmetic">