Re: [boost] [Review] Type Traits Extension by Frederic Bron - Review summary and decision

Subject: Re: [boost] [Review] Type Traits Extension by Frederic Bron - Review summary and decision
From: Joachim Faulhaber (afojgo_at_[hidden])
Date: 2011-04-30 10:49:35

2011/4/29 Joachim Faulhaber <afojgo_at_[hidden]>:
> 2011/4/29 Gottlob Frege <gottlobfrege_at_[hidden]>:
>> On Thu, Apr 28, 2011 at 10:27 PM, Joseph Wu <josephclwu_at_[hidden]> wrote:
>>> On 04/28/2011 07:57 PM, Joachim Faulhaber wrote:
>>>>
>>>> To save you some time, I have inserted my proposal as column D into the
>>>> Wiki at
>>>> https://svn.boost.org/trac/boost/wiki/GuideLines/Naming/OperatorTraitNames
>>>>
>>>> Cheers,
>>>> Joachim
>>>
>>> +1 for column D
>>>
>>> Cheers,
>>>
>>> Joseph
>>
>> I think (in order of strength of my opinion)
>> - naming is very important
>> - plus-equal (et al) is better than any of the other options
>
> interesting ...
> ... could you give us a deeper insight in the superiority of this
> particular name?

Hi Tony,

I'm still wondering about your preference for "plus_equal". My own
considerations here are these:

I remember a lecture by my professor in compiler construction two
decades ago, who raged against the use of operator = in c. I'd be
stupid to assign the assignment semantics to an operator = that is
used in maths with a semantics of "is equal to" for centuries. He
preferred to use := for assignment and = for equality. I agreed with
him then and I still agree today.

Alas ranting and raving of professors didn't influence c: Operator =
is associated to assignment and operator == is associated to equality.
And because we were drilled differently in maths, one of the most
frequent error amongst c-novices was buried in code like

if(x=y)..

that led to seemingly bizarre behavior, both on the program's and on
the programmer's part.

Once attached to the = sign, the assignment semantics is used
consistently in c and later c++

x += y   for x = x + y

assign after plus. In contrast to

x +:= y  for  x := x + y

in the family of algol languages.
Similar for other operations o

x o= y   for  x = x o y

This perfectly justifies

plus_assign for +=

if + is named plus and
   = is named assign

at least I think so ...

Cheers,
Joachim

-- 
Interval Container Library [Boost.Icl]
http://www.joachim-faulhaber.de