[fpc-devel] Templates / Generics

[Florian Klaempfl]

dannym wrote:

> hmm.. a parameter declaration of a function declaration is not a
> declaration block ? I've always thought of them like local variables,
> just happening to be pre-filled..

procedure p(a : array[0..10] of longint);

isn't possible either.
> 
> and, will TList<integer> and mylist be compatible types ?
> 
> 
>>Maybe we need an exception to this when supporting sub routine templates:
>>procedure<T> p(mylist : TList<T>);
>>begin
>>...
>>end;
>>but this doesn't lead to an ambigious syntax.
>>
>>- instantiation steps which require code generation are done after main
>>program compilation based on information saved in the unit files, this
>>has some advantages:
> 
> 
> you mean to save the parse tree of the generic (both the interface and
> the implementation section) to the ppu ? 

Inlining does this already, the infrastructure is in place.

> I've been thinking about using
> a extra file in order not to taint the ppu but if it is possible to use
> the ppu itself for that, i'm all for it :)
> 
> 
>>- several equal instantiations require only one specialisation
> 
> 
> 
>>- it's possible to setup an symbol environment as it has been used in
>>the template definition, so the cyclic unit use problem is void it
>>requires though that a lot symbols of the implementation part of a unit
>>must be written to the unit file if the unit contains a template definition
> 
> 
> note that line number information for nice error messages need to be
> retained along with the parse tree of the generic (so that when another
> unit uses a generic unit but specializes it to something stupid,
> programmer gets a nice location of error rather than "guess where it
> was" :)). 
> Maybe it already is done, though :)
> 
> Note that for the error message, you'll need _two_ locations: one of the
> generic type implementation where the actual error manifested and one
> for the location of the specialization of the generic, to know what has
> been used as the type parameter.
> 
> On second though, _maybe_ just one location (the first) and the names of
> the types used for the type parameters suffice.

For Inlining this works too.

> 
> 
>>This approach will require some compiler clean ups but that isn't that
>>bad ;)
>>
>>Any comments :)?