Templates in classes => what is wrong?

[Xan]

On Tuesday, 17 April 2012 at 15:21:30 UTC, Dejan Lekic wrote:
> On Tuesday, 17 April 2012 at 14:57:18 UTC, Xan wrote:
>> 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.
>
> For an example, you can't use function-pointer to access 
> non-static methods, while with delegates you can. You can see 
> some examples on http://www.dlang.org (Languate Reference).

So, I deduce it's better to use delegater than function?