[fpc-devel] Templates / Generics

[Florian Klaempfl]

I read the disussion above and I'll post my thoughts so far below:

- we'll use a syntax as close as possible to Chrome, e.g.
type
  TList<T> = class
    ...
  end;

- instantiation will be only possible in declaration blocks, not in code
blocks:
possible:
var
  mylist : TList<integer>;
const
  mylist : TList<integer> = nil;
type
  mylist = TList<integer>;
forbidden:
procedure p(mylist : TList<integer>);
begin
  ...
  mylist:=TList<integer>.create;
  ...
end;
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:
- 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

This approach will require some compiler clean ups but that isn't that
bad ;)

Any comments :)?