[PATCH] Math::BigInt->new($n)->bnok($k) incorrect for $k==0 and $k===$n-1 #10601
Comments
From pfusik@op.plThis is a bug report for perl from pfusik@op.pl, There is a bug in Math::BigInt's implementation of n over k: Attached is a patch. Flags: Site configuration information for perl 5.12.1: Configured by 1 at Thu Jul 29 16:39:48 2010. Summary of my perl5 (revision 5 version 12 subversion 1) configuration: Locally applied patches: @INC for perl 5.12.1: Environment for perl 5.12.1: |
From pfusik@op.plMath-BigInt-bnok.patchdiff --git a/cpan/Math-BigInt/lib/Math/BigInt.pm b/cpan/Math-BigInt/lib/Math/BigInt.pm
index f97e438..303f4a0 100644
--- a/cpan/Math-BigInt/lib/Math/BigInt.pm
+++ b/cpan/Math-BigInt/lib/Math/BigInt.pm
@@ -1320,18 +1320,17 @@ sub bnok
}
else
{
- # ( 7 ) 7! 7*6*5 * 4*3*2*1 7 * 6 * 5
- # ( - ) = --------- = --------------- = ---------
- # ( 3 ) 3! (7-3)! 3*2*1 * 4*3*2*1 3 * 2 * 1
+ # ( 7 ) 7! 1*2*3*4 * 5*6*7 5 * 6 * 7 6 7
+ # ( - ) = --------- = --------------- = --------- = 5 * - * -
+ # ( 3 ) (7-3)! 3! 1*2*3*4 * 1*2*3 1 * 2 * 3 2 3
- # compute n - k + 2 (so we start with 5 in the example above)
- my $z = $x - $y;
- if (!$z->is_one())
+ if (!$y->is_zero())
{
+ my $z = $x - $y;
$z->binc();
my $r = $z->copy(); $z->binc();
my $d = $self->new(2);
- while ($z->bacmp($x) <= 0) # f < x ?
+ while ($z->bacmp($x) <= 0) # f <= x ?
{
$r->bmul($z); $r->bdiv($d);
$z->binc(); $d->binc();
diff --git a/cpan/Math-BigInt/lib/Math/BigInt/Calc.pm b/cpan/Math-BigInt/lib/Math/BigInt/Calc.pm
index 52e33d2..6527b38 100644
--- a/cpan/Math-BigInt/lib/Math/BigInt/Calc.pm
+++ b/cpan/Math-BigInt/lib/Math/BigInt/Calc.pm
@@ -1264,7 +1264,7 @@ sub _is_even
sub _is_odd
{
- # return true if arg is even
+ # return true if arg is odd
(($_[1]->[0] & 1)) <=> 0;
}
@@ -1536,22 +1536,20 @@ sub _nok
# ref to array, return ref to array
my ($c,$n,$k) = @_;
- # ( 7 ) 7! 7*6*5 * 4*3*2*1 7 * 6 * 5
- # ( - ) = --------- = --------------- = ---------
- # ( 3 ) 3! (7-3)! 3*2*1 * 4*3*2*1 3 * 2 * 1
-
- # compute n - k + 2 (so we start with 5 in the example above)
- my $x = _copy($c,$n);
+ # ( 7 ) 7! 1*2*3*4 * 5*6*7 5 * 6 * 7 6 7
+ # ( - ) = --------- = --------------- = --------- = 5 * - * -
+ # ( 3 ) (7-3)! 3! 1*2*3*4 * 1*2*3 1 * 2 * 3 2 3
- _sub($c,$n,$k);
- if (!_is_one($c,$n))
+ if (!_is_zero($c,$k))
{
+ my $x = _copy($c,$n);
+ _sub($c,$n,$k);
_inc($c,$n);
my $f = _copy($c,$n); _inc($c,$f); # n = 5, f = 6, d = 2
my $d = _two($c);
- while (_acmp($c,$f,$x) <= 0) # f < n ?
+ while (_acmp($c,$f,$x) <= 0) # f <= n ?
{
- # n = (n * f / d) == 5 * 6 / 2 => n == 3
+ # n = (n * f / d) == 5 * 6 / 2
$n = _mul($c,$n,$f); $n = _div($c,$n,$d);
# f = 7, d = 3
_inc($c,$f); _inc($c,$d);
diff --git a/cpan/Math-BigInt/t/bigintpm.inc b/cpan/Math-BigInt/t/bigintpm.inc
index 87140ba..317e5ed 100644
--- a/cpan/Math-BigInt/t/bigintpm.inc
+++ b/cpan/Math-BigInt/t/bigintpm.inc
@@ -2346,9 +2346,12 @@ NaN:1:NaN
1:-2:0
# 7 over 3 = 35
7:3:35
-7:6:1
+7:6:7
100:90:17310309456440
100:95:75287520
+2:0:1
+7:0:1
+2:1:2
&bround
$round_mode('trunc')
0:12:0
|
From [Unknown Contact. See original ticket]Applied, after some slight fixups, as |
|
@rafl - Status changed from 'new' to 'resolved' |
Migrated from rt.perl.org#77640 (status was 'resolved')
Searchable as RT77640$
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