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? -- Martin Bonner Project Leader PI SHURLOK LTD Telephone: +44 1223 441434 / 203894 (direct) Fax: +44 1223 203999 Email: martin.bonner@pi-shurlok.com www.pi-shurlok.com disclaimer