Larry Wall wrote: > Aaron Sherman writes: > : On Thu, Oct 25, 2001 at 11:30:00AM +1000, Damian Conway wrote: > : > > : > Glenn wrote: > : > > : > > > Have I missed anything? > : > > > : > > Perhaps you've missed one thing. > : > > > : > > [snip] > : > > > : > > Perl 6 could provide a pragma to produce a warning on the first > : > > run-time auto-numerification (compile time would be really hard to > : > > do), together with a selection of different string numerification > : > > methods for extracting the numeric values, for a variety of types > : > > of numeric values. > : > > : > I believe this would be covered by the ability to lexically redefine > : > C<operator:+($)>. > : > : Hmm... this seems dangerous. In general a "numeric context" was imposed > : in Perl5 by the function that needed it by calling SvNV. The overhead > : that I see from externalizing that, and forcing: > : > : $x + $y > : > : To implicitly be: > : > : +($x) + +($y) > : > : is rather large (three times the stack management, type checking, etc).... > : Is this really what we want? > > That depends on whether operator:+ is truly identified with the > internal numerifying function. In the first one, the internal numerify > might only be called if numerification is actually needed. In the > second one, it would potentally be forced. > > There are a number of internal functions that may or may not be > identified with a particular operator. Some of these show up as > non-operator keys in Perl 5's overloading scheme, but there could be > others. Even some that are identified with particular operators are > called intrinsically in places that don't use the operator in question. > > In any event, we need to realize that lexically scoped overrides might > interfere with overloading. What will you do if $x or $y has its own > ideas of what unary + ought to do? Seems to me that we have to make > overloading override the lexically scoped operator, if the lexically > scoped operator is pretending to be the built-in default numerify. > > Larry
So then the lexically scoped operator:+ wouldn't be able to achieve the goal of my suggested implicit numerification warning... the goal being the ability to ensure that there are no implicit numerifications, that all numerifications are done via a selected conversion methed. That sounds like something that would be nice to ensure, in many programs, kind of like -w or use strict, or undef, it helps find things that might be overlooked. -- Glenn ===== Due to the current economic situation, the light at the end of the tunnel will be turned off until further notice.
