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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: do { quit; } else { }
Date: Sun, 6 Apr 2025 12:05:40 +0200
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On 04/04/2025 21:23, 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*/
>    }
> 

This does not strike me as worth the effort as a control block.  There 
are always vast numbers of ways to make different kinds of control 
blocks in a language - the trick is to pick enough to be able to write 
code conveniently, and not so many that it is hard to learn the language 
and understand the code.

Modern languages often have some kind of try/except structure, which is 
what this looks like.  But I don't think that is a good idea to try to 
bolt onto a C compiler as an extension - it would give little benefit 
and a lot of incompatibility.  It is best done as a more fundamental 
part of a language design.  Without integration in the library, all you 
have is syntactic sugar for a "goto" without even saving much typing.


Now, if you were to invent a do / undo control block, where the "undo" 
statement not merely exits the control block but undoes the effect of 
everything done so far inside the block, /then/ you would have something 
new and exciting!