Library Typedefs are fundamentally broken

[Andrei Alexandrescu via Digitalmars-d]

On 9/23/14, 8:10 AM, Wyatt wrote:
> On Monday, 22 September 2014 at 17:21:50 UTC, Andrei Alexandrescu wrote:
>>
>> I would agree with that. If I'd do it over again I'd probably make the
>> string the second argument with no default.
>>
> That's not the problem though.
>
>>> You can make the argument that it's not that much of a burden. And on
>>> a cursory read, sure, that makes enough sense.
>>
>> It's a good argument. At some point some RTFM is necessary; I think
>> it's reasonable to assume that whoever is in the market for using
>> Typedef would spend a minute with the documentation.
>>
> Even just reading this thread, I can see that the people in the market
> for using Typedef also want to use it _often_ (a sentiment I echo)
> because trivial type safety is such a compelling feature.

I'm not buying this. Yah, there's batteries of types a la Windows' 
definitions, but it's not like casual use everywhere.

> The fact that
> it's documented is beside the point. (I thought you or Walter talked
> before about how "RTFM" isn't a shining endorsement of your API?)

Sure, the lesser the better. But it's a continuum, not beside the point.

> The
> fact that its primary use isn't the default presents a usability
> problem.  For one thing, no one likes writing boilerplate.  It's
> annoying.  When things are annoying, people find some other way.  But
> there's another aspect that makes this even worse (below).

Then define and use defineTypedef. Clearly there's an imbalance between 
the desire of getting work done with Typedef and that of ildly arguing 
that Typedef is useless.

People who need to get work done won't be stopped by Typedef. They'll 
type it twice and if they need it a third time then they'll figure how 
to simplify its usage. Or they use Adam's idiom (Adam makes this point 
in his epic slideless talk: just get into it and make it work! I've 
never seem Adam working himself to a foam over minutia.)

>> Type safety is not the problem here. I do agree that surprising
>> behavior for those who don't RTFM is possible.
>>
> I beg to differ.  Type safety is the entire goal.

That's a loose use of the term.

> Surprising behaviour
> shouldn't be the default when the "Surprise!" part is that it doesn't
> break until later.  That surprises should explode spectacularly at their
> earliest convenience is a lesson you taught me with e.g. the rationale
> behind using NaN as the floating point init value.  By failing to
> detonate, errors can manifest in the implementation subtly after
> appearing to work for an extended period.  This is bad.

Not buying all this, sorry.

> You said earlier it's reasonable to assume people would read the docs,
> and I agree to an extent.  But I think it's reasonable to want APIs in
> the standard library that are resistant to misreading, skimming, and
> misunderstanding.  That very sort of confusion is why this thread even
> started, after all!

The guy who started this thread was explained what to do, replied with 
"Sorry, my mistake" and went on his way getting stuff done.

> And the solution in this case is conceptually simple.

What would that be?

>> I'd agree with that. (Again if I could do things over again there'd be
>> no default for the cookie.) But my understanding is
>
> Generating a unique cookie if one isn't given is the correct behaviour
> from the _user's_ perspective.  I believe it also addresses the concerns
> Timon raised regarding Typedef in templates.

I'd be fine with improving Typedef. In fact part of the rationale for 
replacing the built-in with a library type is that we have more 
flexibility in library space.

>> that there's quite a bit of blowing this out of proportion.
>>
> I agree some of the discussion has been hyperbolic, but I also agree
> there's a real problem with the current situation that goes beyond
> simply "this is moderately annoying".
>
>> It's an anecdote. How you explained matters matters a lot :o). I find
>> the requirement for the cookie perfect.
>>
> Something like, "Look how cool it is that we can do typedefs as a
> template!" and a link to the docs.  Just an anecdote from a non-D user
> that ended up being relevant. (I'm trying to score converts! ;)

That's great.


Andrei