Arbitrary function as template parameter?

Arbitrary function as template parameter?

[Lally Singh]

Hi.  I'm writing a g++ extension to give more type information via a 
'special' template type_description<>.  Yeah, 'special' templates are 
kludge-esque, but I was able to figure out how to do it this way faster 
than via more __builtins.

I can do this:

struct foo {};

int i = std::type_description<foo>::is_pod;

But I can't do this:

int foo();

typename std::type_description<foo>::return_type	val = foo();


As parser.c (while very readable) scares me, I'd rather not do any 
changes to the grammar.  So, can I declare a template to either take in 
a type or a function, or at least another template that can take an 
arbitrary function as a parameter?


-- 
Life is short, give up early.


--  
Government is not reason, it is not eloquence, it is force; like fire, 
a troublesome servant and a fearful master.  Never for a moment should 
it be left to irresponsible action.
- George Washington

Re: Arbitrary function as template parameter?

[Phil Edwards]

On Thu, Sep 25, 2003 at 08:21:20PM -0400, Lally Singh wrote:
> Hi.  I'm writing a g++ extension to give more type information via a 
> 'special' template type_description<>.  Yeah, 'special' templates are 
> kludge-esque, but I was able to figure out how to do it this way faster 
> than via more __builtins.

See http://www.devphil.com/~pme/reflection.html and search these lists'
archives for mention of the cxx-reflection development branch.


> As parser.c (while very readable) scares me, I'd rather not do any 
> changes to the grammar.  So, can I declare a template to either take in 
> a type or a function, or at least another template that can take an 
> arbitrary function as a parameter?

Nope, not without changes to the grammar.

-- 
Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it.
    - Brian W. Kernighan

[Solved] Re: Arbitrary function as template parameter?

[Lally Singh]

Ok.  Never mind :-)
std::type_description<__typeof__(foo)> should do what I want..

--  
Government is not reason, it is not eloquence, it is force; like fire, 
a troublesome servant and a fearful master.  Never for a moment should 
it be left to irresponsible action.
- George Washington