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: 2010-01-30 14:35:06

On 01/30/10 00:37, Hicham Mouline wrote:
> Hello,
>  
> struct params {
>   double field1;
>   double field2;
>   double field3;
>   double fiedl4;
> };
>  
> I would like to generate all the types that hold any combination of the 
> members of params.
[snip]

Step1:
   Create cross-product of void and {field1,field2,...}.
   This will produce a sequence of pairs:

    no_yes =
      ( (void,field1)
      , (void,field2)
      ...
      , (void,fieldn)
      )

Step2:

   Create the crosss product of all rows in no_yes.

   cross_no_yes =
     ( (void,void,..void)
     , (field1,void,...void)
     , (void,field2,void...,void)
     ...
     , (field1,field2,...fieldn)
     )

step3:

   remove all the voids in all the rows of cross_no_yes.

Since the size<no_yes> == n and each element in that row is size 2,
the cross_no_yes size would be 2^n.  Then simply rm the all void row.

Not tested.