Re: [boost] If boost::fusion is the hammer, then what's the nail?

From: Larry Evans (cppljevans_at_[hidden])
Date: 2006-12-14 11:12:35

On 12/14/2006 08:52 AM, Thorsten Ottosen wrote:
[snip]
> 
> I have used tuples in a similar manner, but I kinda think its not the 
> best to do; a named tuple would be more appropriate, or maybe just a struct.
> 
> What bothers me is the self-explanatory properties are lost; I can't 
> figure out what tuple element that means what by just looking at the 
> code. Is it
> 
>    tie(eval,dev1,dev2) = find_root(...)
> 
> or
> 
>    tie(dev1,dev2,eval) = find_root(...)
> 
> ?
> 
This "named tuple" is essentially the composite_product whose test
code is here:

http://boost.cvs.sourceforge.net/boost-sandbox/boost-sandbox/libs/indexed_types/test/composite_product_test.cpp

Instead of field names, numerators in an enumeration are used.  For 
example, in the above test, the numerators, {a,b,c} of the enumeration, 
indices, correspond to the field names in the following struct:

   struct
r_struct
{
     field_ndx<a> a_field;
     field_ndx<b> b_field;
     field_ndx<c> c_field;
};