the ++ operator

[Sidirourgos Lefteris]

Ioannis Papaioannou wrote:

> Steve Stavropoulos wrote:
>
>> On Thu, 20 Nov 2003, Vasilis Vasaitis wrote:
>
> [snip]
>
>>>     c = a[i] + b[i++];
>>
> [snip]
>
>>> έχουν undefined behaviour, όπως λέμε, δηλαδή ο compiler κάνει ό,τι
>>> γουστάρει, οπότε δε βασιζόμαστε και τις γράφουμε κάπως αλλιώς.
>>
>>
>>  La8os! O compiler symfwna me thn ansi c exei _plhrws_ defined 
>> symperifora otan blepei to ++ ws prefix h postfix. Otan einai prefix 
>> tote to increment 8a ginei PRIN to evaluation ths ypoloiphs protashs, 
>> enw otan einai postfix tote to increment 8a ginei META to evaluation 
>> ths ypoloiphs protashs.
>
>
> Symfwna me thn ansi c kai to manual pou diabases, mporeis na 
> apanthseis me sigouria sto parakatw (gia olous tous ansi c compilers)?
>
> H ekfrash gia i = 0:
> c = a[i]+b[i++] + a[i]+b[i];
>
> antistoixei me poio apo ta parakatw:
> 1) c = a[0] + b[1] + a[0] + b[0];
> 2) c = a[0] + b[1] + a[1] + b[1];
> 3) c = a[1] + b[1] + a[0] + b[0];
> 4) c = a[1] + b[1] + a[1] + b[1];

Oxi akribws:) to b[1] ths deyterhs sthlhs sto paradeigma sou, 8a einai 
panta b[0]. Mhn 3exnas oti to ++ meta to telesth (i++) ay3anei ton 
telesth meta thn xrhsh toy, ena to ++ prin to telesth (++i) ton ay3anei 
prin thn xrhsh toy. Genika h parastash c = a[i]+b[i++] + a[i]+b[i]; 
mporei na bgalei 2^3 diaforetika apotelesmata!

lefteris

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