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Postings from April 2004
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Moin,
On Wednesday 14 April 2004 22:20, Tassilo von Parseval wrote:
> On Wed, Apr 14, 2004 at 08:22:19PM +0200 Tels wrote:
> "0 but true" is no different from, say, "0 and true" when it comes to
> converting it to a number (it's 0 both times). The difference is that "0
> but true" wont ever trigger a warning. This is intentional and you will
> find this special case by grepping through the perl source.
*sigh* another of these "special" cases in Perl. How should BigInt handle
this? I think it should be NaN.
Other modules have similiar "problems":
te@null:~> perl -MMath::GMP -le 'print Math::GMP->new("0 but true") + 1'
1
te@null:~> perl -MMath::GMP -le 'print Math::GMP->new("0 but true") + 2'
2
te@null:~> perl -MMath::GMP -le 'print Math::GMP->new("0but true") + 2'
2
te@null:~> perl -MMath::GMP -le 'print Math::GMP->new("01but true") + 2'
2
te@null:~> perl -MMath::GMP -le 'print Math::GMP->new("01but 3true") + 2'
2
te@null:~> perl -MMath::GMP -le 'print Math::GMP->new("NaN") + 2'
2
te@null:~> perl -MMath::GMP -le 'print Math::GMP->new("1") + 2'
3
Whatever BigInt should do, the current behaviour is quite old:
# perl -IMath-BigInt-0.01/lib/ -MMath::BigInt -lwe 'print
$Math::BigInt::VERSION'
0.01
# perl -IMath-BigInt-0.01/lib/ -MMath::BigInt -lwe 'print
Math::BigInt->new("0 but true")+9'
NaN
> That's what dualvars usually do. A variable has such a split personality
> whenever
>
> $var+0 ne $var;
>
> Whether you give priority to the numerical or the string slot is a
> semantic issue. Since Math::BigInt->new takes a string as argument,
> using the string slot would seem more plausible. Whichever way you do
> it, it should be documented.
Ok. I prefer the string version, too.
(While that might cause problems with libraries that are confused by
dual-vars I think it can be worked around).
Cheers,
Tels
- --
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