Re: [Swig-devel] Re: Perl test harness (was Re: [Swig-cvs] SWIG/Examples/test-suite operator_overload.i,1.7,1.8)

[Marcelo M. <mm...@ac...>]

Mathieu Bouchard wrote:

>On Sun, 8 Jan 2006, Marcelo Matus wrote:
>
> =20
>
>>Also, it seems from here
>> http://www.perl.com/doc/manual/html/lib/overload.html
>>that the logical operators (&&,||) are not in the list of operators, an=
d the
>>"~" and "!" are understood as bit operators.
>>note that in python you can't overload 'and' or 'or' either, so, it see=
ms a
>>common issue.
>>   =20
>>
>
>"~" is a bit operator and belongs to the same family as "&" "|" "^".
>
>"!" is not a bit operator, it would belong in the same family as "&&"=20
>"||" given the way it understands its values, but unlike the two others,=
=20
>it's not a shortcircuit operator, so it's a special case among the speci=
al=20
>cases. Why it was put in "bit operators" is possibly to avoid putting it=
=20
>alone in a category of its own.
> =20
>
well, then the question is, is this a documentation issue or an=20
implementation issue? I guess
we need to check in the source code what the operator '!" does.

in python, for example, "!/not' is a very strange beast too, because the=20
'and' and 'or' are not
real operators, they are part of the grammar. If you write:

   s =3D p and q;  =20

that behaves like the shell 'and' operator, ie if 'p' is false then 'q'=20
is never evaluated, and there is
such thing as a call to p.__logical_and__(q), the operator is resolved=20
at the "parsing" stage.

but for bit operators

  s =3D p & q;

is resolved as =20
=20
  s =3D p.__and__(q);

since in python __and__ is the bit operator, not the logical operator.


if that is the case in perl too, ie, that 'and/&&' and 'or/||' are part=20
of the grammar, then they
can't be overloaded.

>"and" "or" "not" are supposed (?) to just be aliases with a different
>priority. Is "not" overloadable? does it just reuse the implementation o=
f=20
>the "!" operator ?
>
> =20
>
do you mean in C++ or perl?, in C++ they are simple aliases, ie, you=20
can't define both.
(but you can declare both as long as the declarations are equivalent).


> _ _ __ ___ _____ ________ _____________ _____________________ ...
>| Mathieu Bouchard - t=E9l:+1.514.383.3801 - http://artengine.ca/matju
>| Freelance Digital Arts Engineer, Montr=E9al QC Canada
>
> =20
>