Subject: Re: [boost] [type_erasure] default implementation of concept signatures
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-05-28 16:16:25
AMDG
On 05/28/2011 12:42 PM, Pyry Jahkola wrote:
> On 2011-05-28 21:59:57 +0300, Matt Calabrese said:
>
>> On Sat, May 28, 2011 at 2:55 PM, Steven Watanabe
>> <watanabesj_at_[hidden]>wrote:
>>
>>> I don't have the concepts proposal handy, but
>>> doesn't LessThanComparable have an axiom that
>>> requires that (a < b) is equivalent to (b > a)?
>>>
>>
>> Yes.
>>
>> axiom Consistency(T a, T b) {
>> (a > b) == (b < a);
>> (a <= b) == !(b < a);
>> (a >= b) == !(a < b);
>> }
>
> For what it's worth, e.g. NaN's are an exception to that rule...
>
It's not an exception. The axiom only applies to
LessThanComparable types. Technically, double
isn't LessThanComparable, because it violates this
rule.
In Christ,
Steven Watanabe