Re: Using std::equal with an empty set.
Vladimir Grigoriev wrote:
From mathematical point of view an empty set is a subset of any set
indeed. However if to follow the Standard description it seems that in
this case std::equal must return false. Because according to the
Standard the following for example condition must hold
pred( *i, *( first2 + ( i - first1 ) ) )
As this condition does not hold for any itearator from [first, last) why
should std::equal return true?
Actually, that condition holds for all elements in that range. Note that
there are effectively no dereferenceable iterators in that range because
first==last, hence also no elements. Note that the STL docs are probably
more explicit there, they are talking about two subsets of equal length
that are compared.
BTW, since you seem to look for thing you can flag as ambiguous (is it a
crusade you're on, btw?), also consider that string("abc").find("") returns
zero. ;)
Good luck!
Uli
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