I was wondering if D had something akin to std::function in C++.

Say I have some functions in an associative array, for example:

     auto mapping = ['!' : (string a) => toUpper!string(a), '^' : (string a) => capitalize!string(a)];

What I want to do is basically declare something like:

    function string(string) transform;
    if(<some condition>) {
         transform = mapping[<lookup>];
    }

In C++, this could be done by declaring:

     std::function<string(string)> transform;

Is there an equivalent D construct for this?

On 6/25/2014 10:10 AM, Yuushi wrote:
> I was wondering if D had something akin to std::function in C++.
>
> Say I have some functions in an associative array, for example:
>
>       auto mapping = ['!' : (string a) => toUpper!string(a), '^' :
> (string a) => capitalize!string(a)];
>
> What I want to do is basically declare something like:
>
>      function string(string) transform;
>      if(<some condition>) {
>           transform = mapping[<lookup>];
>      }
>
> In C++, this could be done by declaring:
>
>       std::function<string(string)> transform;
>
> Is there an equivalent D construct for this?

For function pointers (free functions or static class functions):

alias TransformFunc = string function( string );
TransformFunc transform;

if( foo ) transform = &func;

For delegates (lambdas or pointers to class methods or inner functions):

alias TransformDg = string delegate( string );
TransformDG transform;

if( foo ) transform = &bar.method;

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On 6/25/2014 10:45 AM, Mike Parker wrote:
> On 6/25/2014 10:10 AM, Yuushi wrote:
>> I was wondering if D had something akin to std::function in C++.
>>
>> Say I have some functions in an associative array, for example:
>>
>>       auto mapping = ['!' : (string a) => toUpper!string(a), '^' :
>> (string a) => capitalize!string(a)];
>>
>> What I want to do is basically declare something like:
>>
>>      function string(string) transform;
>>      if(<some condition>) {
>>           transform = mapping[<lookup>];
>>      }
>>
>> In C++, this could be done by declaring:
>>
>>       std::function<string(string)> transform;
>>
>> Is there an equivalent D construct for this?
>
> For function pointers (free functions or static class functions):
>
> alias TransformFunc = string function( string );
> TransformFunc transform;
>
> if( foo ) transform = &func;
>
> For delegates (lambdas or pointers to class methods or inner functions):
>
> alias TransformDg = string delegate( string );
> TransformDG transform;
>
> if( foo ) transform = &bar.method;
>

And in this case you want the latter:

TransformDg transform = mapping[ '!' ];


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On Wednesday, 25 June 2014 at 01:47:13 UTC, Mike Parker wrote:
> On 6/25/2014 10:45 AM, Mike Parker wrote:
>> On 6/25/2014 10:10 AM, Yuushi wrote:
>>> I was wondering if D had something akin to std::function in C++.
>>>
>>> Say I have some functions in an associative array, for example:
>>>
>>>      auto mapping = ['!' : (string a) => toUpper!string(a), '^' :
>>> (string a) => capitalize!string(a)];
>>>
>>> What I want to do is basically declare something like:
>>>
>>>     function string(string) transform;
>>>     if(<some condition>) {
>>>          transform = mapping[<lookup>];
>>>     }
>>>
>>> In C++, this could be done by declaring:
>>>
>>>      std::function<string(string)> transform;
>>>
>>> Is there an equivalent D construct for this?
>>
>> For function pointers (free functions or static class functions):
>>
>> alias TransformFunc = string function( string );
>> TransformFunc transform;
>>
>> if( foo ) transform = &func;
>>
>> For delegates (lambdas or pointers to class methods or inner functions):
>>
>> alias TransformDg = string delegate( string );
>> TransformDG transform;
>>
>> if( foo ) transform = &bar.method;
>>
>
> And in this case you want the latter:
>
> TransformDg transform = mapping[ '!' ];
>
>
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> This email is free from viruses and malware because avast! Antivirus protection is active.
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Thanks a ton - I guess I need to do a fair bit more reading about alias.

On Wednesday, 25 June 2014 at 03:33:15 UTC, Yuushi wrote:
>
> Thanks a ton - I guess I need to do a fair bit more reading about alias.

In this case, alias acts as typedef in C++. What is important here is the function pointers/delegates syntax.

On Wednesday, 25 June 2014 at 05:13:00 UTC, Olivier Pisano wrote:
> On Wednesday, 25 June 2014 at 03:33:15 UTC, Yuushi wrote:
>>
>> Thanks a ton - I guess I need to do a fair bit more reading about alias.
>
> In this case, alias acts as typedef in C++. What is important here is the function pointers/delegates syntax.

Yeah, I realised that when I went back and looked at what I'd tried:

     function string(string) transform;

which should have been:

    string function(string) transform;

which does work.

Thanks for the clarification.

On 06/24/2014 08:33 PM, Yuushi wrote:

> I guess I need to do a fair bit more reading about alias.

It is probably too basic for you but somebody else may find it useful:

 http://ddili.org/ders/d.en/lambda.html

Ali

On 06/24/2014 11:23 PM, Yuushi wrote:

> Yeah, I realised that when I went back and looked at what I'd tried:
>
>       function string(string) transform;

That gets me all the time! :-/ That is the long version of the function literal syntax:

    auto f = function string(string s) { return "hello"; };

>
> which should have been:
>
>      string function(string) transform;
>
> which does work.
>
> Thanks for the clarification.

Ali