Re: [Boost-Users] Typelists.

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2001-11-27 23:54:17

Hi James,

A typelist is, well, a list of types :)

One easy way to create a list of types is to use std::pair to create a
lisp-style list. Suppose I want to create a list of three types: int, char,
and std::string.

typedef std::pair< int, std::pair<char, std::pair<std::string, nil> > >
  MyTypeList;

The nil at the end is a type to mark the end of the list.

I can access the first thing in the list like this:

MyTypeList::first_type

I can access the second thing in the list like this:

MyTypeList::second_type::first_type

In general, one uses recursive algorithms to manipulate these kinds of
lists. You can write template metaprograms for these recursive algorithms.
Horrors! :)  (I do it all the time, its fun!)

Cheers,
Jeremy

On 11/27/01 11:40 PM, "jamescurran_at_[hidden]" <jamescurran_at_[hidden]> wrote:

> Over on the Boost Developer group, there a lot of talk about how to
> best implement a typelist.  Just so I can follow that discussion,
> could someone give me the basic thumbnail sketch of what exactly a
> typelist is, and what they are used for?
> 
> 
> 
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-- 
Jeremy Siek                          http://www.osl.iu.edu/~jsiek
Ph.D. Student, Indiana Univ. B'ton   email: jsiek_at_[hidden]
C++ Booster (http://www.boost.org)   office phone: [phone]