pre Math::BigInt v1.72

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

diff --git a/lib/Math/BigInt.pm b/lib/Math/BigInt.pm
index 7393b12..b84ad36 100644 (file)
--- a/lib/Math/BigInt.pm
+++ b/lib/Math/BigInt.pm
@@ -18,7 +18,7 @@ package Math::BigInt;
 my $class = "Math::BigInt";
 require 5.005;
 
-$VERSION = '1.70';
+$VERSION = '1.72';
 use Exporter;
 @ISA =       qw( Exporter );
 @EXPORT_OK = qw( objectify bgcd blcm); 
@@ -1140,6 +1140,14 @@ sub bsub
     return $x;
     }
 
+  require Scalar::Util;
+  if (Scalar::Util::refaddr($x) == Scalar::Util::refaddr($y)) 
+    {
+    # if we get the same variable twice, the result must be zero (the code
+    # below fails in that case)
+    return $x->bzero(@r) if $x->{sign} =~ /^[+-]$/;
+    return $x->bnan();          # NaN, -inf, +inf
+    }
   $y->{sign} =~ tr/+\-/-+/;    # does nothing for NaN
   $x->badd($y,@r);             # badd does not leave internal zeros
   $y->{sign} =~ tr/+\-/-+/;    # refix $y (does nothing for NaN)
@@ -2027,17 +2035,15 @@ sub bfround
 
 sub _scan_for_nonzero
   {
-  # internal, used by bround()
-  my ($x,$pad,$xs) = @_;
+  # internal, used by bround() to scan for non-zeros after a '5'
+  my ($x,$pad,$xs,$len) = @_;
  
-  my $len = $x->length();
-  return 0 if $len == 1;               # '5' is trailed by invisible zeros
+  return 0 if $len == 1;               # "5" is trailed by invisible zeros
   my $follow = $pad - 1;
   return 0 if $follow > $len || $follow < 1;
 
-  # since we do not know underlying represention of $x, use decimal string
-  my $r = substr ("$x",-$follow);
-  $r =~ /[^0]/ ? 1 : 0;
+  # use the string form to check whether only '0's follow or not
+  substr ($xs,-$follow) =~ /[^0]/ ? 1 : 0;
   }
 
 sub fround
@@ -2087,8 +2093,8 @@ sub bround
   $pad = $len - $scale;
   $pad = abs($scale-1) if $scale < 0;
 
-  # do not use digit(), it is costly for binary => decimal
-
+  # do not use digit(), it is very costly for binary => decimal
+  # getting the entire string is also costly, but we need to do it only once
   my $xs = $CALC->_str($x->{value});
   my $pl = -$pad-1;
 
@@ -2106,7 +2112,7 @@ sub bround
     ($digit_after =~ /[01234]/)                        ||      # round down anyway,
                                                        # 6789 => round up
     ($digit_after eq '5')                      &&      # not 5000...0000
-    ($x->_scan_for_nonzero($pad,$xs) == 0)             &&
+    ($x->_scan_for_nonzero($pad,$xs,$len) == 0)                &&
     (
      ($mode eq 'even') && ($digit_round =~ /[24680]/) ||
      ($mode eq 'odd')  && ($digit_round =~ /[13579]/) ||
@@ -2118,8 +2124,8 @@ sub bround
        
   if (($pad > 0) && ($pad <= $len))
     {
-    substr($xs,-$pad,$pad) = '0' x $pad;
-    $put_back = 1;
+    substr($xs,-$pad,$pad) = '0' x $pad;               # replace with '00...'
+    $put_back = 1;                                     # need to put back
     }
   elsif ($pad > $len)
     {
@@ -2128,7 +2134,7 @@ sub bround
 
   if ($round_up)                                       # what gave test above?
     {
-    $put_back = 1;
+    $put_back = 1;                                     # need to put back
     $pad = $len, $xs = '0' x $pad if $scale < 0;       # tlr: whack 0.51=>1.0  
 
     # we modify directly the string variant instead of creating a number and
@@ -2143,7 +2149,7 @@ sub bround
     $xs = '1'.$xs if $c == 0;
 
     }
-  $x->{value} = $CALC->_new($xs) if $put_back == 1;    # put back in if needed
+  $x->{value} = $CALC->_new($xs) if $put_back == 1;    # put back, if needed
 
   $x->{_a} = $scale if $scale >= 0;
   if ($scale < 0)