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From: bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: do { quit; } else { }
Date: Fri, 4 Apr 2025 21:18:45 +0100
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On 04/04/2025 20:23, Thiago Adams wrote:
>    What do you think of this control block?
> 
>    do
>    {
>       FILE f = fopen("file.txt", "r");
> 
>       if (f == NULL) quit; /*goes to else part*/
> 
>       /*success here*/
>       for (int i =0; i < 10; i++){
>           ...
>           if (error) quit;
>       }
> 
>    }
>    else
>    {
>       /*some error*/
>    }
> 

As a new language feature?

I think 'do {}' would be confused 'do {} while' (a parser - or a human - 
won't know this isn't a loop until the 'else' is seen. And then there's 
a possibility that that 'else' belongs to an 'if' but an omission or 
inclusion of a braces has screwed things up.

Perhaps a new keyword ('try' maybe) is better.

You'd also need to specify how nested do-else blocks will work. Or will 
'quit' (so you have a new keyword anyway) only work at this level?

What about chained versions: do {} else do {} else ...; I guess 'quit' 
will just go to the next else block rather than quit the whole chain?

Note that this can be emulated in C now using:

    if
    {
      goto quit001;
    }
    else
    {quit001:
    }

Perhaps what C needs is a way to do that jump without an explicit goto:

    if
    {
      quit001;
    }
    else
    {quit001:
    }

You can require that such jumps can only go forwards.