Steven Watanabe wrote:
AMDG
[*slightly* off-topic: Does that mean Ad maiorem Dei gloriam?]
On 07/22/2012 07:21 AM, Markus Werle wrote:
Hi Steven!
I have one question: proto and spirit use _1, _2, etc. TypeErasure uses _a, _b, _c ... What was your reason to introduce yet another placeholder set?
http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/... I disagree with this decision. You write:
An earlier version of the library used the names _1, _2, etc. instead of _a, _b, etc. This caused a certain amount of confusion because the numbered placeholders are already used by several other libraries including Boost/Std Bind, Boost.Phoenix, and Boost.MPL.
IMHO the introduction of another set of placeholders is more confusing. If we are to discriminate here, we can do it via namespaces - and of course one day it is std::_1 for all of us. Just because your library is the first to use _a, _b, _c what does that mean for future (boost) libraries that use some kind of placeholders? Do they have to use _aa, _bb, etc.? To me placeholders are such a natural concept I do not care about having some kind of "deja vu" here. To the contrary: The meaning (placeholder) is identical so we should use identical names.
I eventually decided that since the placeholders represented named parameters instead of positional parameters, letters were more appropriate than numbers.
Indeed the naming is arbitrary. Starting from the same observation (_1 is already available in boost::*) I draw the opposite conclusion: Use these names for the sake of symmetry and hope for convergence of concepts over the years. @Review Master: Should I miss the end date for reviews, take this as my mini subset of a review: I'd prefer _1, _2 instead of _a, _b. Markus