Templates in classes => what is wrong?

[Xan]

On Tuesday, 17 April 2012 at 01:31:43 UTC, Kenji Hara wrote:
> On Monday, 16 April 2012 at 18:48:52 UTC, Xan wrote:
>> On Sunday, 15 April 2012 at 19:30:27 UTC, Ali Çehreli wrote:
>>> On 04/15/2012 11:39 AM, Xan wrote:
>>> > On Sunday, 15 April 2012 at 11:23:37 UTC, John Chapman 
>>> > wrote:
>>> >> On Sunday, 15 April 2012 at 11:16:43 UTC, Xan wrote:
>>> >>>
>>> >>> int main(string [] args)
>>> >>> {
>>> >>> auto alg = Algorisme!(int,int);
>>> >>
>>> >> Should be:
>>> >> auto alg = new Algorisme!(int, int);
>>> >>
>>> >>> alg.nom = "Doblar";
>>> >>> alg.versio = 1;
>>> >>> alg.funcio = (int a) {return 2*a};
>>> >>
>>> >> Should be:
>>> >> alg.funcio = (int a) { return 2 * a; };
>>> >> or:
>>> >> alg.funcio = a => 2 * a;
>>> >>
>>> >>> }
>>> >
>>> >
>>> > It does not work:
>>> >
>>> > $ gdmd-4.6 algorisme.d
>>> > algorisme.d:18: Error: variable algorisme.main.alg voids 
>>> > have
>>> no value
>>> > algorisme.d:18: Error: expression class Algorisme is void 
>>> > and
>>> has no value
>>> >
>>> > with the code https://gist.github.com/2394274
>>> >
>>> > What fails now?
>>> >
>>> > Thanks,
>>> > Xan.
>>>
>>> Your code is still missing 'new':
>>>
>>> 	auto alg = new Algorisme!(int, int);
>>
>> With only this change, I receive this error:
>>
>> $ gdmd-4.6 algorisme.d
>> algorisme.d:21: Error: cannot implicitly convert expression 
>> (__dgliteral1) of type int delegate(int a) pure nothrow to int 
>> function(int)
>>
>>>
>>> Unrelated recommendations:
>>>
>>> - Return 0 from main() for successful exit, anything else by 
>>> convention means some sort of error.
>>>
>>> - Take advantage of constructors (and 'alias') to simplify 
>>> syntax and risk of bugs:
>>>
>>> import std.conv, std.stdio, std.stream, std.string;
>>> import std.socket, std.socketstream;
>>> import std.datetime;
>>>
>>> class Algorisme(U,V) {
>>>   string nom;
>>>   uint versio;
>>>   alias V function (U) Funcio;
>>>   Funcio funcio;
>>>
>>>   this(string nom, uint versio, Funcio funcio)
>>>   {
>>>       this.nom = nom;
>>>       this.versio = versio;
>>>       this.funcio = funcio;
>>>   }
>>> }
>>>
>>> int main(string [] args)
>>> {
>>>   alias Algorisme!(int, int) MeuAlgorism;
>>>   auto alg = new MeuAlgorism("Doblar", 1,
>>>                              (int a) { return 2 * a; });
>>>
>>>   return 0;
>>> }
>>>
>>> Ali
>>
>> With all of your suggestion [https://gist.github.com/2394274], 
>> I get:
>>
>> $ gdmd-4.6 algorisme.d
>> algorisme.d:30: Error: constructor 
>> algorisme.Algorisme!(int,int).Algorisme.this (string nom, uint 
>> versio, int function(int) funcio) is not callable using 
>> argument types (string,int,int delegate(int a) pure nothrow)
>> algorisme.d:30: Error: cannot implicitly convert expression 
>> (__dgliteral1) of type int delegate(int a) pure nothrow to int 
>> function(int)
>> algorisme.d:27: Error: function D main has no return 
>> statement, but is expected to return a value of type int
>>
>>
>> What fails?
>>
>> PS: Thanks for your recommendations...
>> PPS: By the other hand, I see you have learned catalan 
>> ("MeuAlgorisme"?) ;-)
>
> Problem may be here:
>
>> alg.funcio = (int a) { return 2 * a; };
>
> 2.057 and earlier (You may use gdc 2.057 and command line 
> wrapper gdmd), function literal always deduced as 'delegate'. 
> So this expression raises an error about type mismatching Lhs 
> of 'int function(int)' and  Rhs of 'int delegate(int) pure 
> nothrow'.
>
> Then, specifying explicit 'function' will resolve issue:
>
>   alg.funcio = function(int a) { return 2 * a; };
>
> Bye.
>
> Kenji Hara

Thanks, Kenji. If I change function to delegate in declaration of 
field, it works too. What do you recommend to have delegates or 
functions? What are the benefits and ...

Thanks,
Xan.