David Abrahams wrote:

on Thu Mar 08 2007, Christoph Duelli wrote:

...

Given a struct like struct X { int a; char b; float c; } and some function-'template' f

is it possible to 'generate' - preferably by means of templates, MPL or something of the kind - variations of some function f for each of X's fields?

E.g. I'd like to have functions like int getA() { return a; } char getB() { return b; } float getC() { return c; } ...

(The functions I have in mind are more complex, obviously, but the idea is to generate one such function for all the fields of X.) I would like to avoid writing a macro call or something per field, as I would like the code to work (after recompiling it) even if the definition of X is changed and some fields are added. So, is there some generic 'iterator' over the fields of a struct?

Nope.

You might consider using Boost.Fusion and using a tuple instead of a struct. You won't be able to generate a family of overloaded functions at namespace scope, but you will be able to generate a family of overloaded (static) member functions.

You can also map your struct(s) to a fusion tuple. The mapping can be a simple "tie". Example: fusion::vector map_struct(X& x) { return fusion::tie(x.a, x.b, x.c); } Then you can refer to x.a through at_c<1>, x.b through at_c<2> and x.c through at_c<3>. If you want your fields to be non-positional (i.e. a field named "a" can always be referred to somehow regardless of its position in the struct), then you can use fusion::map and map various keyword types to each of the fields. Example: struct a_; struct b_; struct c_; fusion::result_of::map_tie< a_, int&, b_, char&, c_, float& > map_struct(X& x) { return fusion::map_tie(x.a, x.b, x.c); } Then you can refer to x.a through at_key, x.b through at_key and x.c through at_key. Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net

Gottlob Frege wrote:

On 3/9/07, Joel de Guzman wrote:

...

map_struct(X& x) { return fusion::map_tie(x.a, x.b, x.c);

a_type? return fusion::map_tie(x.a, x.b, x.c); ?

Yep. Sorry. Thanks for the correction! Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net