Re: [boost] [guidelines] why template errors suck

Subject: Re: [boost] [guidelines] why template errors suck
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2010-09-28 15:14:34

  AMDG

On 9/28/2010 10:53 AM, David Abrahams wrote:
> At Tue, 28 Sep 2010 10:12:29 -0700,
> Steven Watanabe wrote:
>> The problem is that concepts force all checks into this realm.
> I don't know what you're getting at, but it might be related to this:
> the fact that concepts do early checking is problematic for many of
> our current TMP idioms, which rely on having checks only at
> instantiation time.  For example, foo<mpl::_1>  couldn't be written if
> foo were a constrained template, unless mpl::_1 just happened to
> satisfy its requirements.

This isn't really what I mean.  I personally avoid using placeholders
anyway, as I've had bad experiences with unexpected instantiations.

> Anyway, yeah, that's a clash.  But maybe in a "concepts" world we
> wouldn't want to do that in the first place.

I'm obviously failing to communicate, so I'll
try to come up with a more concrete example.

In Christ,
Steven Watanabe