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"Bartc" <bc@xxxxxxxxxx> writes:
> bert wrote:
>> On 30 Mar, 19:11, Richard <de...@xxxxxxxxx> wrote:
>>> bert <bert.hutchi...@xxxxxxxxxxxxxx> writes:
>>>> On 30 Mar, 15:02, Philip Potter <p...@xxxxxxxxxxxx> wrote:
>>>>> Rahul wrote:
>
>>>>>> int main()
>>>>>> {
>>>>>> int aa=0,b=0;
>>>>>> 1>0?aa:b = 10;
>>>>>> printf("value %d %d\n",aa,b);
>>>>>> return(0);
>>>>>> }
>>>
>>>>>> and output is value 0 0
>
>>>>> The result of the ?: operator is not an lvalue, and cannot be
>>>>> assigned to.
>>>
>>>>> If you want to conditionally assign to one of two objects, it's
>>>>> probably clearer to write it in full:
>>>
>>>>> if (1>0)
>>>>> aa = 0;
>>>>> else
>>>>> b = 10;
>>>
>>>>> If you really want unreadable code, I suppose you could do this:
>>>>> int *ip[2] = {&b,&aa};
>>>
>>>>> *ip[1>0] = 10;
>>>
>>>>> but if I worked with you I wouldn't thank you for it :)
>>>
>>>> For such requirements, I have written - and
>>>> been satisfied with - code of the style:
>>>
>>>> *(i > 0 ? &aa : &b) = <complicated expression>;
>>>
>>> Well done - you'll make maintainers very happy in years to come.
>>
>> I can't decide whether that's sarcasm from you, or real praise.
>
> I don't think it was praise..
>
>>
>>> What on earth is wrong with
>>>
>>> v= complex expr;
>>> if(i)
>>> aa=v;
>>> else
>>> b=v;
>>>
>>> Same number of characters give or take too .... Easy to see
>>> flow/assignment in a debugger too. Very easy to read.- Hide quoted
>>> text -
>>
>> The main thing "wrong" with your alternative
>> is the omission of a block structure.
>>
>> {
>> int v = complicated expression;
>> if (i)
>> aa = v;
>> else
>> b = v;
>> }
>>
>> would make it perfectly clear to a maintainer
>> in years to come that the only purpose of v
>> was to be assigned either to aa or to b.
>
> There was nothing much wrong with the original syntax:
>
> a ? b : c = x;
>
> (maybe better as (a ? b : c) = x;)
>
> except that C doesn't allow it, and it's unfortunate that the legal format
> is a little messy:
So nothing wrong with it except for the fact that C doesnt allow it? Are
you trolling or just up for some sort of special award?
>
> *(a ? &b ? &c) = x;
>
> This is what the programmer wants to do, so why force him to create
> unnecessary statements and to duplicate expressions, or declare unnecessary
> temporary variables? All extra clutter.
Dont be ridiculous. Everything is a trade off between readability,
maintainability and efficiency. The above is , IMO, too clever for its
own good. And its certainly no more efficient.
>
> Exactly why a?b:c can't appear like that on the left-hand-side of an
> assignment is a bit of a mystery;
There is no mystery about it.
> after all a, a.b, a->b, a[b] and so on can
> all appear on the lhs without the programmer having to insert explicit
> address-of operators.
And that has to do with ?: how?
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