Vicente J. Botet Escriba wrote:
Le 07/04/12 09:13, Robert Ramey a écrit :
Documentation for mpl::less<T> has the following section:
typedef less<c1,c2> r; // a
Return type:Integral Constant. Semantics:Equivalent to struct r : less<c1,c2>::type {}; //b
if //a is used then the following yields bool_<true>
is_same< less<c1, c2>, r>
if // b is used then the following yields bool_<false>
is_same< less<c1, c2>, r>
So in what sense are //a and // b equivalent?
Hi, they are not equivalents. The equivalence relation appears via the
type access.
is_same< less<c1, c2>::type, r::type>
should be true_type in both cases.
This is because integral_constant<typename T, T V> defines a nested typedef 'type' as itself.
Hmmm - this helps understand why I've always been confused about when to use "less<c1,c2>::type" vs "less<c1,c2>". Note that it doesn't clarify my confusion itself - it just clarifies why I've always been confused - which of course is an entirely different thing. So you agree that the statement above (which appears in the documentation)
typedef less<c1,c2> r; // a
Return type:Integral Constant. Semantics:Equivalent to struct r : less<c1,c2>::type {}; //b
is incorrect and misleading? I'm thinking that it shouldn't even be in the documentation as written. This raises the question as to what the documentation should say about the type "less<c1, c2>" ?
HTH, Vicente