Re: [Boost-users] mpl documentation question

7 Apr 2012

      Vicente J. Botet Escriba wrote:
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Le 07/04/12 09:13, Robert Ramey a écrit :
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Documentation for mpl::less<T>  has the following section:
typedef less  r;                    // a
Return type:Integral Constant.
Semantics:Equivalent to
struct r : less::type {};        //b
if //a is used then the following yields bool_<true>
is_same<  less, r>
if // b is used then the following yields bool_<false>
is_same<  less, r>
So in what sense are //a and // b equivalent?
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Hi,
they are not equivalents. The equivalence relation appears via the
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type access.
is_same<  less::type, r::type>
should be true_type in both cases.
This is because integral_constant defines a nested
typedef 'type' as itself.
Hmmm - this helps understand why I've always been confused about
when to use "less::type" vs "less".  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)
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typedef less  r;                    // a
Return type:Integral Constant.
Semantics:Equivalent to
struct r : less::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" ?
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HTH,
Vicente