Re: [boost] Re: is_convertible corner case

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2003-01-24 20:10:50

----- Original Message -----
From: "David Abrahams" <dave_at_[hidden]>

> I tend to agree on a "moral/aesthetic" level, but on a practical level
> we have to tread carefully.  The question, "can we just have an
> operator which produces a compile-time constant value saying whether
> its operand is a valid expression?" has come up a few times in the
> committee.  Each time, the implementors looked at their codebases and
> said "oooh, that's really hard to do."  I think the short form of the
> reason is that C++ compilers generally don't have the ability to
> recover from errors reliably.  That may explain why your 2nd, 3rd,
> 4th... diagnostic messages tend to be useless gibberish ;-)
>
> So, I'd like to push for something like that but practically speaking
> I'm not sure how to get there.

The problems are not insurmountable though (with an "is_valid_expression").
You aren't dealing with entire language at this point, only an expression.
You'd need an independent expression parser that is coupled to the symbol
table.

Paul Mensonides