Re: [Boost-users] [tuple] How to manipulate the types

From: David Abrahams (dave_at_[hidden])
Date: 2006-05-29 13:53:35

Adrián Etchevarne <adrian.etchevarne_at_[hidden]> writes:

> Problem:

>   How can I get a tuple type from a tuples::cons<> list ?

> example:

>   given the type:

>      cons<int, cons<float, cons<int, null_type> > >

>

>   obtain

>      tuple<int, float, int>

>

>

> Real problem:

>    I need to insert a type T at the beginning of a tuple, how I can do this?

>

> example

>    given the type T and  tuple<int, float>, obtain a tuple<T, int, float> 

That's a lot easier to solve, in some sense, than the "Problem:"

above.  The cons list *is* a valid tuple.  So to inserta  new type at

the front, just write

    const<T, the-shorter-cons-list>

You might also want to look at

http://spirit.sourceforge.net/dl_more/fusion_v2/libs/fusion/doc/html/index.html

which was recently accepted into Boost.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com