"David Abrahams" wrote
"Andy Little" writes
"David Abrahams" wrote
"Andy Little" writes
I am not concerned with the intractible problem of sequence identity ( whatever that means) at the moment.
Then what was this indictment about?
Me:
The result of the transform is only required to be "concept-identical" to the result you're looking for.
You: IMO that behaviour is sloppy.
What can I say? I acknowledge that mpl is a monumental piece of work . Wonderful... but far from perfect.
I don't think the fact that it's imperfect gives you the right to label any arbitrary design decision as sloppy.
I dont follow? "any arbitrary decision"?
You seem to have no justification at all for calling the behavior mentioned above "sloppy," notwithstanding that it reminds you of another behavior that you dislike.
The behaviour of having a return type defined as a concept rather than a type in this case is unnecessarily imprecise. In practise (Based on my experience in pqs physical quantities library) it causes an explosion of arbitrary types all meaning the same thing. This in turn leads to slow compile times and overuse of compiler resources and with the fatal effect in some cases, that the compiler cannot cope resulting in a failed compilation. An alternative suggestion is to explicitly specify what seems to be the actual behaviour of arithmetic operations on int_'s, long's etc in the documentation. The actual behaviour seems to be that these functions invariably return an integral_c. It could then also be specified that the value_type of the result is found by applying the usual promotion rules to the types of each of the (non mpl::na) arguments. That would at least tighten up any play in the current specification. In order to get the desired behaviour it would then be a question of only using integral_c's of one value_type. Having said the above its not actually that important to me what mpl does to be honest. I only use it in trivial ways in pqs. Having put it in and taken it of the library out a couple of times I have found I am happier without it, and would be very reluctant to put it back in again. regards Andy Little