fix behavior of <=> on bigints

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

diff --git a/lib/Math/BigInt.pm b/lib/Math/BigInt.pm
index 013e55f..ef4af61 100644 (file)
--- a/lib/Math/BigInt.pm
+++ b/lib/Math/BigInt.pm
@@ -36,6 +36,12 @@ sub stringify { "${$_[0]}" }
 sub numify { 0 + "${$_[0]}" }  # Not needed, additional overhead
                                # comparing to direct compilation based on
                                # stringify
+sub import {
+  shift;
+  return unless @_;
+  die "unknown import: @_" unless @_ == 1 and $_[0] eq ':constant';
+  overload::constant integer => sub {Math::BigInt->new(shift)};
+}
 
 $zero = 0;
 
@@ -76,8 +82,8 @@ sub external { #(int_num_array) return num_str
 # Negate input value.
 sub bneg { #(num_str) return num_str
     local($_) = &bnorm(@_);
-    vec($_,0,8) ^= ord('+') ^ ord('-') unless $_ eq '+0';
-    s/^H/N/;
+    return $_ if $_ eq '+0' or $_ eq 'NaN';
+    vec($_,0,8) ^= ord('+') ^ ord('-');
     $_;
 }
 
@@ -100,7 +106,7 @@ sub bcmp { #(num_str, num_str) return cond_code
     } elsif ($y eq 'NaN') {
        undef;
     } else {
-       &cmp($x,$y);
+       &cmp($x,$y) <=> 0;
     }
 }
 
@@ -384,6 +390,19 @@ are not numbers, as well as the result of dividing by zero.
    '1 23 456 7890'                 canonical value '+1234567890'
 
 
+=head1 Autocreating constants
+
+After C<use Math::BigInt ':constant'> all the integer decimal constants
+in the given scope are converted to C<Math::BigInt>.  This conversion
+happens at compile time.
+
+In particular
+
+  perl -MMath::BigInt=:constant -e 'print 2**100'
+
+print the integer value of C<2**100>.  Note that without convertion of 
+constants the expression 2**100 will be calculatted as floating point number.
+
 =head1 BUGS
 
 The current version of this module is a preliminary version of the