Is typedef an alien?

[language_fan]

Thu, 24 Sep 2009 15:33:38 -0400, Jarrett Billingsley thusly wrote:

> On Thu, Sep 24, 2009 at 2:36 PM, Aenigmatic <procode at adam-dott-com.au>
> wrote:
>> No further response to any responses to my previous post's responses is
>> a both swift and non-invasive.
>>
>> Now my deeply thought question is ...
>>
>> Is typedef (in D) a C/C++ legacy or is the dear orphan now adopted as a
>> first-class citizen in the US of D?
> 
> It's a different beast, and in my experience, pretty useless. Most of
> the time you want typedef'ed types to interact with other types a little
> more richly. Say you want to use a double as a time. Okay, what do you
> get when you subtract two points in time? Not a time, that's for sure.
> You get a time _span_ instead. So you end up implementing them as
> structs.
> 
> Virtually every time I've tried to use typedef, it hasn't sufficed and
> I've ended up using a struct instead. It seems like a failed idea, or at
> the very least, yet another half-thought-out abandoned feature.

I can imagine some uses for it when the type is very simple, and you fear 
that the compiler cannot inline operations on structs. Other than that, 
common mainstream language features like typedefs, variant!(), and enums 
are mere special cases of algebraic datatypes (with some implicit 
syntactic sugar). There are some downsides, too, but I prefer to have the 
more general type in languages that I use.