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

Subject: Re: [boost] [guidelines] why template errors suck
From: Robert Ramey (ramey_at_[hidden])
Date: 2010-09-27 17:41:37

David Abrahams wrote:

> I recall a conversation on this list where someone (named Sebastian?)
> successfully, and impressively, described a semantic relationship
> required between the load/save operations of a read/write archive
> pair.

After many years, that little episode sticks in my mind.  I think it
was Joaquin though.  Actually it was the very episode that
convinced me that the quest for some sort of semantic formality
was destined to be a dead end which ultimate relied on
some sort of shared intuitive understanding of what a sentence
means.  So I concluded one would just as well avoid the attempt
with no real loss.

> That's unrelated to the rest of the conversation, because as I have
> stated many times, validation of template parameters by computer can
> never check semantic constraints.  It's equivalent to solving the
> halting problem.

I think that's what I'm trying to say.

>> I was referring to the usage of the word "concept" in this context.
>> I found this to be very misleading and not at all descriptive of the
>> the function of "checking template parameters at compile time"
>
> Because that's not what a concept is.  That's just one of the most
> important things you can do with a concept.  Concepts are about
> mathematical abstraction.

maybe that's why I had trouble.  I think when I first saw it as I skimmed
through the boost documentation, , I wasn't looking for something one would
describe as "checking template parameters".  That's what I meant
when I said "the nomenclature doesn't help"

Robert Ramey