Re: [Boost-users] generate structs with all combinations of members from a given struct

Subject: Re: [Boost-users] generate structs with all combinations of members from a given struct
From: Larry Evans (cppljevans_at_[hidden])
Date: 2010-02-01 14:35:38

On 02/01/10 03:08, Hicham Mouline wrote:
>  
> 
>     ----- Original Message -----
>     *From:* Hicham Mouline <mailto:hicham_at_[hidden]>
>     *To:* boost-users_at_[hidden] <mailto:boost-users_at_[hidden]>
>     *Sent:* Monday, February 01, 2010 12:09 PM
>     *Subject:* Re: [Boost-users] generate structs with all combinations
>     of members from a given struct
>      
> 
> My previous runtime solution was wrong.
> I just fixed it now.

I had a hard time understanding how it worked.
A simpler solution would be to just generate the
characteristic functions for sets of a given size.
The characteristic function could then be used
to select elements from the set:

http://en.wikipedia.org/wiki/Characteristic_function

The structure of such a program is very similar to yours
in that it has a recursive call and a for loop.  However, with
this method, the for loop just has size 2.  The depth of
recursion is n, where n is size of the set.  I think your
method had recursion depth of n-1.

The attached illustrates the method.
Output is:

size=32
  0 0 0 0 0
  1 0 0 0 0
  0 1 0 0 0
  1 1 0 0 0
  0 0 1 0 0
  1 0 1 0 0
  0 1 1 0 0
  1 1 1 0 0
  0 0 0 1 0
  1 0 0 1 0
  0 1 0 1 0
  1 1 0 1 0
  0 0 1 1 0
  1 0 1 1 0
  0 1 1 1 0
  1 1 1 1 0
  0 0 0 0 1
  1 0 0 0 1
  0 1 0 0 1
  1 1 0 0 1
  0 0 1 0 1
  1 0 1 0 1
  0 1 1 0 1
  1 1 1 0 1
  0 0 0 1 1
  1 0 0 1 1
  0 1 0 1 1
  1 1 0 1 1
  0 0 1 1 1
  1 0 1 1 1
  0 1 1 1 1
  1 1 1 1 1

-regards,
Larry