Avoid creating GV with NULL name when vivifying nameless scalars.

[p5sagit/p5-mst-13.2.git] / lib / integer.pm

diff --git a/lib/integer.pm b/lib/integer.pm
index a88ce6a..f6be58a 100644 (file)
--- a/lib/integer.pm
+++ b/lib/integer.pm
@@ -12,11 +12,33 @@ integer - Perl pragma to compute arithmetic in integer instead of double
 
 =head1 DESCRIPTION
 
-This tells the compiler that it's okay to use integer operations
+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.
 
+Note that this affects the operations, not the numbers.  If you run this
+code
+
+    use integer;
+    $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>.
 
 =cut