Templates in classes => what is wrong?

[Kenji Hara]

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