Steven Watanabe wrote:
AMDG
On 04/07/2012 10:47 AM, Robert Ramey wrote:
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?
<snip> 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>" ?
is_same doesn't work, but what you can use is mpl::equal_to. mpl::equal_to compares integral constants for equality without requiring the types to match exactly:
equal_to<less<c1, c2>, r> -> mpl::true_
That's interesting and useful. So I guess my problem is with the usage of the term "equivalent". I had interpreted this as "can be substituted for". So I'm now thinking that my original concern is justified - that the document doesn't accurately convey what "less<c1, c2>" really is. This has always been confusing to me - and still is. I totally get what "less<c1, c2>::type" is supposed to mean but the meaning and intended usage of "less<c1, c2>" is still lost on me.
In Christ, Steven Watanabe