Comma operator = broken design

[so]

On Fri, 09 Dec 2011 03:19:34 +0200, Robert Jacques <sandford at jhu.edu>
wrote:

> On Thu, 08 Dec 2011 13:17:44 -0500, so <so at so.so> wrote:
>
>> On Thu, 08 Dec 2011 19:25:10 +0200, Dejan Lekic <dejan.lekic at gmail.com>
>> wrote:
>>
>>>>
>>>> type a = a + 2; // compiles with no errors, no warnings, no explosions
>>>> (that i know of)
>>>
>>> If "type" has the default initialiser, then what is the problem?
>>
>> What does it do in both C and D context?
>> 1. It does different things.
>> 2. C version even worse because of debug/release difference.
>> 3. If D still does this, it violates the B-D rule (either does the same
>> thing or doesn't compile at all. Actually there are many things violate
>> this rule...)
>>
>> type a; // even this simple code violates B-D rule.
>>
>> What is the use case?
>> . Is there any?
>> . If there is not any you think, but still compiler allows it, it
>> generates nothing but bugs (from experience :) ).
>>
>> Question should be, why does it exist at all?
>
> Actually, these statements don't violate the B-D rule. In C/C++ the  
> value of 'a' prior to use is implementation defined (i.e. it is  
> undefined by the spec) and in practice tends to be some random stack  
> value. D just sets that value to a consistent default, which is  
> completely compliant with the C spec.

I disagree. As you said while in C/C++ same thing gets assigned random  
values,
in D it doesn't. As a result, it changes both the coders' expectations and  
programs
outcome. Even the definitions are different. Undefined there and defined  
here.
I am not sure how to express this.

As far as i understand you are saying; Because uninitialized variables are  
undefined in C,
D can act as another C compiler and interpret this rule as it pleases. But  
in practice no compiler i know does that.
And "assuming the variable initialized to some value" is a bad programming  
practice, which i should say the most popular among its kind.
So it clashes with another thing about D, pragmatism.