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

From: John Maddock (john_at_[hidden])
Date: 2006-12-14 08:35:16

Weapon Liu wrote:
> I personally very like this fancy facility, and that's why I present
> these mumbles here to annoy you guys( if so, my apologies go here:-))
> Any comments?

I can give you one use I have for tuples:

I have a piece of boilerplate code that accepts a tuple (of any size) and 
prints out either a csv file or a boost::array C++ code conaining the data 
passed.

It allows me to output data for graphing, or matrixes of test data very 
quickly just by creating a short function that returns a tuple, and then 
passing that function to my boilerplate.  If I want more columns of data I 
just increase the size of tuple by 1.

I suppose I could have used a vector instead, but it's less elegant somehow.

I've also used tuples in place of struct's whenever I have an API that needs 
to return more than 2 items.  For example I have some root finding 
algorithms that accept a unary functor whose root is to be found: the 
functor returns a tuple containing the function evaluation, plus the first 
two derivatives.  Using a tuple here simplified both implementation and 
documentation. Had I felt the need, I could have performed compile time 
dispatch to different algorithms based on how many derivatives were 
available (the tuples size).

HTH, John.