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Op Thu, 3 Nov 2005, schreef Mattias Gaertner:
>Here is a proposal of the syntax:
>
>type
> TGenericClass<T,F> = class
> public
> procedure Add(Item: T; Flag: F);
> end;
This syntax is almost impossible to implement since in one of your other
mails the symbols to mark the parameters appear in regular source code:
begin
generictypeA<integer>.create
end.
It will be very hard for the parser to see the difference in advance
between:
variable<integer(another_var)
generic_type<integer
Only when the > symbol is parsed the result is known.
No, already after the second token after the opening "<". It must either be a ",", or the closing bracket.
Assuming that you disallow something like generic_type<generic_type2<...
Even that limitation can be overcome by disallowing directly nested generic use specification. Something like
type
TGeneric2 = generic_type2<...>;generic_type<TGeneric2 ...
could be allowed however.
Maybe the parser may be able lookup the type first and make a decision based on that, but it would be in the middle of a recursive expression parse designed for infix operators.
Simply use a second, third, ... lookahead token for the < case.
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Also in C++ this sometimes causes trouble where you need to change your
code notation so the compiler eats it. I don't know if this proposal
suffers from this mess, but we should avoid at all cost to import it into
Pascal.
From: Mattias Gaertner
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On Thu, 3 Nov 2005 19:59:40 +0100 (CET)
Daniël Mantione wrote:
Right. I didn't think of that.
What about edged brackets?
type
TGenericClass[T,F] = class
public
procedure Add(Item: T; Flag: F);
end;
procedure TGenericClass.Add(Item: T; Flag: F);
// Note: No redundant [T,F] after TGenericClass.
begin
end;
type TListOfComponent = TGenericList[TComponent];
Analog:
type TGenericListClass[T] = class of TGenericList[T];
type PGenericRecord[T] = ^TGenericRecord[T];
procedure GenericProc[T](Param: T);
begin
end;
I think this has a similar problem to the other one. Consider this:
my_procedure[...
where my_procedure isn't an instantiation of a method using the generic but a function returing an array of something.
Not completely sure whether this is a problem though... depends on the implementation.
Regards,
Thomas