Re: [Boost-users] A forward iterator need not be default-constructible

Subject: Re: [Boost-users] A forward iterator need not be default-constructible
From: Andrew Sutton (asutton.list_at_[hidden])
Date: 2011-10-02 17:51:51

>> Singular values crop up in all kinds of contexts, BTW.  Do ints support
>> division?  Well, yes, unless the denominator is zero.
>
> I'm sorry. This is completely wrong. 0 is value -- a state of an
> numeric type -- just like singularity is the state of some iterators.
> In fact, I think you actually prove Chris' point, here; you've just
> extended the notion of singularity from iterators to integers. I would
> take that to mean that singularity is independent of type.

I should amend my previous statements.

Maybe singularity is best viewed as a property of an expression. 0 is
certainly a valid integral value. Unfortunately, there are no general
named iterator values. What's a singular state for one may not be a
singular state for another. I think an interesting question is, "what
are the general properties of iterators that causes operations on them
to result in singularity?". When is *i defined?