foreach thoughts

[Jakob Ovrum]

On Tuesday, 14 January 2014 at 13:04:58 UTC, Timon Gehr wrote:
> On 01/14/2014 11:09 AM, Jacob Carlborg wrote:
>> On 2014-01-14 09:36, Jakob Ovrum wrote:
>>
>>> You'll have to get used to the exclamation mark, otherwise 
>>> you'll never
>>> be able to fully appreciate D's generic programming. I quite 
>>> like it - I
>>> don't think there's anything objectively ugly about it.
>>
>> Or, in this case, fix the compiler to be able to inline 
>> delegates. Or is
>> there any other advantage of using an alias parameter instead 
>> of a
>> delegate?
>>
>
> 1. It is likely to result in faster code when inlining fails. 
> Eg. it will often not allocate when the delegate would, due to 
> nested template instantiation simplifying escape analysis.
>
> 2. IFTI limitations. Eg. the following cannot work with the 
> current language unless 'map' is specialized to ranges of int:
>
> [1,2,3].map(x=>2*x)

3. Lazy ranges don't have to carry around delegates.

4. Algorithms can specialize depending on the argument function. 
However, this is currently only possibly when string lambdas are 
used... (e.g. std.algorithm.startsWith does this)

5. Alias parameters receiving function templates have the benefit 
of being able to instantiate the function template argument 
multiple times with different template arguments. This is murky 
territory when it comes to function literals with inferred 
parameter types though - they are not guaranteed to be 
implemented in terms of function templates.