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From: Bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: else ladders practice
Date: Fri, 1 Nov 2024 13:39:10 +0000
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On 01/11/2024 12:55, fir wrote:
> Bart wrote:
>> On 01/11/2024 11:32, fir wrote:
>>> Bart wrote:
>>>> ral clear patterns here: you're testing the same variable 'n' against
>>>> several mutually exclusive alternatives, which also happen to be
>>>> consecutive values.
>>>>
>>>> C is short of ways to express this, if you want to keep those
>>>> 'somethings' as inline code (otherwise arrays of function pointers or
>>>> even label pointers could be use
>>>
>>> so in short this groupo seem to have no conclusion but is tolerant
>>> foir various approaches as it seems
>>>
>>> imo the else latder is like most proper but i dont lkie it optically,
>>> swich case i also dont like (use as far i i remember never in my code,
>>> for years dont use even one)
>>>
>>> so i persnally would use bare ifs and maybe elses ocasionally
>>> (and switch should be mended but its fully not clear how,
>>>
>>> as to those pointer tables im not sure but im like measurad it onece
>>> and it was (not sure as to thsi as i dont remember exactly) slow maybe
>>> dependant on architecture so its noth wort of use (if i remember
>>> correctly)
>>
>> Well, personally I don't like that repetition, that's why I mentioned
>> the patterns. You're writing 'n' 5 times, '==' 5 times, and you're
>> writing out the numbers 1, 2, 3, 4, 5.
>>
>> I also don't like the lack of exclusivity.
>>
>> However I don't need to use C. If those 'somethings' were simple, or
>> were expressions, I could use syntax like this:
>>
>>     (n | s1, s2, s3, s4, s5)
>>
> 
> on a C ground more suitable is
> 
> {s1,s2,s3,s4,s5)[n]
> 
> //which is just array indexing

No, it's specifically not array indexing, as only one of s1 - s5 is 
evaluated, or nothing is when n is not in range, eg. n is 100.

You could try something like that in C:

     int x;

     x = ((int[]){(puts("a"),10), (puts("b"),20), (puts("c"), 30), 
(puts("d"),40)})[3];

     printf("X=%d\n", x);

The output is:

    a
    b
    c
    d
    X=40

Showing that all elements are evaluated first. If index is 100, the 
result is also undefined.