auto parameter causing template (suggestion for D)

[david]

在 Sat, 23 Sep 2006 12:54:48 +0800，Reiner Pope  
<reiner.pope at REMOVE.THIS.gmail.com> 写道:

> david wrote:
>> take a look at this:
>>  import std.stdio;
>> void myoverload(auto foo)
>> {
>> static if (is ( typeof(foo):int ) )
>>     { writefln("int");
>>     }
>> else
>>     static if (is ( typeof(foo):char[] ) )
>>     { writefln("char[]");
>>     }
>> }
>> void main()
>> {
>>  myoverload(3);
>>  myoverload("asdkjf");
>> }
>>   Though this is a trivial improvement to D language. but I think that  
>> affect people differently in their mind. People would no longer notice  
>> they are writing a template for that myoverload
>> People would see that function as a normal function.
>> Though that would lost the type information where we can get from void  
>> myoverload(T)(T t) directly from T, I think typeof(foo) won't bother  
>> too much! And it's really elegant way to implement in that way.
>
> Yes, it's quite elegant. This suggestion is similar to mine from 'Some  
> more template syntax sugar,' but yours has the advantage of an  
> unambiguous syntax (since auto is a keyword, it can't be used as a  
> type). Add this to type inference of return values, and you get dead  
> easy templating, or compile time duck typing, in other words. (adding  
> return type inference basically means that every type can be inferred,  
> and typeof expressions shouldn't be needed much)
>
> The example I posted earlier:
>
> T sqr(T) (T x)
> {
>      return x*x;
> }
>
> would become
>
> auto sqr(auto x)
> {
>      return x*x;
> }
>
> and the compiler would understand this to be equivalent to:
>
> typeof(__ret) sqr(__t1) ( __t1 x)
> {
>      auto __ret = x * x;
>      return __ret;
> }
>
> This could work very well.
>
> Cheers,
>
> Reiner

Yeah, auto can be generalized to return type too. Good point. This way is  
quite elegant. Hope we can see that in dmd 0.168 :p

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