John M. Dlugosz said [off-list]:
> Darren Duncan |Perl 6| wrote:
>> I also know that
>> given its current design, === and !=== just happen to have the same
>> semantics as logical xnor and xor when given 2 Bool inputs, and so
>> they serve the purpose.  Having distinct xnor and xor operators is
>> useful from partly a documentation perspective and from
>> error-checking; a strict compiler or runtime should complain if
>> non-Bool inputs are given to them.
> With the heritage as a free-typed language, the use of different
> operators rather than overloading an operator based on type was a core
> feature of Perl.  You might not have two typed Bool arguments.  You have
> two arguments which might be considered boolean, or numeric, or string,
> depending on what I want of it at the moment.
> So !=== between two arrays still does the Bool meaning, and asks if one
> is empty and the other not.  More serious with strings, which can be
> strings or the serialized form of something else.  === with strings will
> be False if one contains "0" and the other contains "false", when both
> are the same as XML attribute values of type XSD:boolean.

Actually, I'll correct myself.  In Perl, I would expect the
boolean-specific operators like and/or/xor/etc to accept any values at all
as arguments, and evaluate them in a boolean context, using each object's
notion of truthness.  But my point is that, though the behaviour of xor
and !=== is very different in the general case, when given two actual Bool
arguments, their semantics would be the same, and so someone working in a
pure Bool context would get the desired behaviour from !=== and ===
treated as xor and xnor. -- Darren Duncan

Reply via email to