(Cross-posting for now, but please follow up on boost-users only.) On 2/3/2011 12:06 AM, Robert Ramey wrote:

I've been studying proto/fusion/phoenix. Becoming familiar with this stuff takes quite an effort. It's quite interesting though. And it seems ideal for a project I want to do. But I do have one question:

phoenix/Function objects Functional/ Proto/ PolymorphicFunctionObject ?

All seem to address function objects. There seems to be a lot of overlap and it's not clear to me which I should be using for what. That is, each library seems to address function objects from a different perspective, but there is not summary which contrasts them. I need a "function object library Decoder Ring". Are there any documents which would help me out?

Lots of libraries define function objects or tools for creating them. That's true for Phoenix and Proto (both tools for creating function objects). Phoenix helps you define general purpose function objects in-place (lambdas). Proto helps you define function objects specifically for manipulating expression trees (grammars w/ semantic actions). PolymorphicFunctionObject is a concept that function objects must model if they are to be usable with boost::result_of. Function objects created by Phoenix and Proto all model PolymorphicFunctionObject. I don't know anything about boost/functional. HTH, -- Eric Niebler BoostPro Computing http://www.boostpro.com