Re: [boost] [Boost.Parameter] questions and advice

From: Martin Bonner (Martin.Bonner_at_[hidden])
Date: 2007-07-10 09:33:33

From: Andrew Sutton 

> On Jul 10, 2007, at 9:02 AM, Cédric Venet wrote:
> 
>> 
>>> 2. I've run into the situation where parameters are truly optional -
>>> they don't specify default values, but optional components to an
>>> algorithm. What's the best way to implement this? How can I test
>>> (within a function) to determine if a parameter has been passed or
>>> not? I've hacked together an approach using a `not_given` struct. Is
>>> there something already like this in the library.
>> 
>> boost.optional should serve your purpose.
> 
> I had previously considered that as an option (no pun).
> Unfortunately, I don't think this helps if I choose to adopt a
> compile-time function selection. Otherwise, it would work very nicely
> at runtime. I've still got it on my short list of solutions.

I'm not clear what your "truly optional" parameters are actually for, but if (for example) they supply a functor could the default value be some sort of identity functor?

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