Operator overloading

[Xan]

On Thursday, 19 April 2012 at 20:59:05 UTC, Jonathan M Davis 
wrote:
> On Thursday, April 19, 2012 21:14:43 Xan wrote:
>> Hi, I read http://dlang.org/operatoroverloading.html but in my
>> code it does not work. I tried to overload '*' binary operator 
>> in
>> my class Algorisme:
>> 
>> [...]
>> class Algorisme(U,V) {
>> string nom;
>> uint versio;
>> alias V function (U) Funcio;
>> Funcio funcio;
>> 
>> this(string nom, uint versio, Funcio funcio) {
>> try {
>> this.nom = nom;
>> this.versio = versio;
>> this.funcio = funcio;
>> }
>> catch {
>> writeln("Error");
>> }
>> }
>> 
>> string toString() {
>> return format("%s (versió %s): %s -> %s", nom, versio,
>> typeid(U), typeid(V));
>> }
>> 
>> Algorisme(U, V) opBinary(string op) (Algorisme(U, V) alg) {
>> static if (op == '*') return new Algorisme(U,V)("composició",
>> this.versio+alg.versio, this.funcio);
>> }
>> 
>> }
>> [...]
>> 
>> but I receive these errors:
>> 
>> $ gdmd-4.6 algorisme.d
>> algorisme.d:31: function declaration without return type. (Note
>> that constructors are always named 'this')
>> algorisme.d:31: no identifier for declarator Algorisme(U, V)
>> algorisme.d:31: semicolon expected following function 
>> declaration
>> algorisme.d:31: function declaration without return type. (Note
>> that constructors are always named 'this')
>> algorisme.d:31: function declaration without return type. (Note
>> that constructors are always named 'this')
>> algorisme.d:31: found 'alg' when expecting ')'
>> algorisme.d:31: no identifier for declarator
>> opBinary(Algorisme(U, V))
>> algorisme.d:31: semicolon expected following function 
>> declaration
>> algorisme.d:31: Declaration expected, not ')'
>> algorisme.d:35: unrecognized declaration
>> 
>> 
>> Why it fails?
>> Anyone could help me?
>
> Use a template constraint rather than a static if. As it 
> stands, any operator
> other than "*" will result in a function with no return 
> statement.
>
> Algorisme opBinary(string op)(Algorisme alg)
>  if(op == "*")
> {
>  return new Algorisme("composició", this.versio+alg.versio, 
> this.funcio);
> }
>
> - Jonathan M Davis

Thanks, Jonathan. I suppose with 'if' (dynamic), it generates 
Exception if we call with other operator than '*', isn't?

Thanks,
Xan.