In the web I found the following definition of LessThanComparable
concept that was intended to show how axioms work:

concept LessThanComparable<typename T> {
  bool operator<(T, T);

  axiom Irreflexivity(T x) { !(x < x); }

  axiom Asymmetry(T x, T y) {
    if (x < y) !(y < x);
  }

  axiom Transitivity(T x, T y, T z) {
    if (x < y && y < z) x < z;
  }
}

Now, in N2322 the definition of LessThanComparable doesn't use axioms,
but instead provides a human-readable text "operator< is a strict weak
ordering relation".

Is it intentional?


Thanks,
&rzej

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On Jul 2, 1:29 pm, restor <akrze...@interia.pl> wrote:
> In the web I found the following definition of LessThanComparable
> concept that was intended to show how axioms work:
[snip example]
> Now, in N2322 the definition of LessThanComparable doesn't use axioms,
> but instead provides a human-readable text "operator< is a strict weak
> ordering relation".
>
> Is it intentional?

Yes. Those axioms depend on the left- and right-hand types being
exactly the same ('T'). The LessThanComparable in N2322 has different
left- and right-hand types (T and U), so we can't really express the
axioms.

We have considered adding a concept StrictWeakOrdering<T> that refines
LessThanComparable<T, T> and contains those axioms.

  - Doug

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