shortcut for dynamic dispatch and operators

[Pelle Månsson]

Andrei Alexandrescu wrote:
> KennyTM~ wrote:
>> On Dec 1, 09 22:30, Steven Schveighoffer wrote:
>>> An idea I just had when thinking about how ugly opDispatch and opBinary
>>> operators will be if we get those was, wouldn't it be cool if the
>>> compiler could translate:
>>>
>>> myTemplateMethod("abc" || "def")() if(condition) {}
>>>
>>> to
>>>
>>> myTemplateMethod(string __x)() if((__x == "abc" || __x == "def") &&
>>> condition) {}
>>>
>>> It makes dispatch based on compile-time strings much more palatable, for
>>> example:
>>>
>>> opDispatch("foo" || "bar")() {...}
>>> opBinary("+" || "-" || "*")(int rhs) {...}
>>>
>>> instead of:
>>>
>>> opDispatch(string fn)() if(fn == "foo" || fn == "bar") {...}
>>> opBinary(string op)() if(op == "+" || op == "-" || op == "*")(int rhs)
>>> {...}
>>>
>>> In fact, it can be generalized to any type which has literals:
>>>
>>> factorial(int x)(){ return factorial!(x-1)() * x;}
>>> factorial(1)() { return 1;}
>>>
>>> What I don't know is if the || works in all cases -- because something
>>> like true || false is a valid expression. Maybe someone can come up with
>>> a better way.
>>>
>>> -Steve
>>
>> Alternative suggestion:
>>
>> Make "x in y" returns a bool and works for arrays. Then you can write
>>
>> int opBinary(string s)(int rhs) if (s in ["+", "-", "*", "/", "^", 
>> "|", "&"]) { ... }
>>
> 
> It's a bit difficult to see a very thin operator mask a linear 
> operation, but I'm thinking maybe "x in y" could be defined if y is a 
> compile-time array. In that case, the compiler knows the operation and 
> the operand so it may decide to change representation as it finds fit.
> 
> Andrei
What do you suggest using when you need to find out if an object is in 
an array? Arrays lacking opIn bothers me.