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Re: I have a confession to make...

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Thiago Adams <thiago.adams@gmail.com> writes:

> On Sunday, August 15, 2021 at 6:44:35 PM UTC-3, Keith Thompson wrote:
>> Vir Campestris <vir.cam...@invalid.invalid> writes: 
>> > I've been writing C, and more lately C++, since some time in the 1980s. 
>> > 
>> > I've just written a goto. I know it's evil, and I shouldn't do it, but 
>> > just this once... 
>> > 
>> > And it isn't in any of the serious stuff I do in may day job either. 
>> > 
>> > You all know what a magic square is - a square where all the columns, 
>> > rows, and diagonals add up to the same value. 
>> > 
>> > I'm messing about doing it for a cube. Wikipedia says you can't for 
>> > small cubes. 
>> > 
>> > I have a square for the base, and a centre value, and therefore I can 
>> > work out all the values for the top square as they are on diagonals 
>> > with one of the bottom values and the centre one. 
>> > 
>> > I therefore have 3 nested loops: centre value, X and Y coordinates. 
>> > 
>> > And if I don't like the result I jump out of the X Y loops. Which is 
>> > where I have that goto.
>> Breaking out of a nested loop is one legitimate use case for a goto. An 
>> alternative is to separate the inner loop into another function and use 
>> return rather than goto. That might not be practical. And it's always 
>> *possible* to write without gotos (there's a theorem to that effect), 
>> but sometimes at the cost of making the code more difficult to read. 
>> 
>> As I wrote here: 
>> https://softwareengineering.stackexchange.com/a/133523/33478 
>> 
>> The main use of a goto in a reasonably modern language (one that 
>> supports if/else and loops) is to simulate a control flow construct 
>> that's missing from the language. 
>> 
>> I'd like to see an extended "break" (and "continue") that refers to the 
>> name of the loop to be broken -- note: not the code location to which it 
>> jumps, but the name of the construct that's being affected. A number 
>> of other languages have this kind of named break (Ada, Perl, etc.). 
>>
>
> I miss some jumps in C and I am using macros just to give gotos a more
> structured meaning.
>
> #define try  if (1)
> #define catch else catch_label:
> #define throw goto catch_label
>
> try {
>    if (error) throw;
>
>   //success
> } 
> catch {
>   //error situation
> }

I don't think hiding a goto in a macro does anything to ameliorate the
potential problems.  It seems to me it's just going to make things
worse.

-- 
Ben.

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Thread

I have a confession to make... Vir Campestris <vir.campestris@invalid.invalid> - 2021-08-15 22:14 +0100
  Re: I have a confession to make... Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-08-15 14:44 -0700
    Re: I have a confession to make... Thiago Adams <thiago.adams@gmail.com> - 2021-08-15 15:56 -0700
      Re: I have a confession to make... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-08-16 01:50 +0100
  Re: I have a confession to make... Bart <bc@freeuk.com> - 2021-08-16 00:18 +0100
  Re: I have a confession to make... DFS <nospam@dfs.com> - 2021-08-15 20:31 -0400
  Re: I have a confession to make... David Brown <david.brown@hesbynett.no> - 2021-08-16 08:20 +0200
    Re: I have a confession to make... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-08-15 23:21 -0700
    Re: I have a confession to make... Vir Campestris <vir.campestris@invalid.invalid> - 2021-08-17 21:43 +0100
  Re: I have a confession to make... Mark Bluemel <mark.bluemel@gmail.com> - 2021-08-16 00:32 -0700
    Re: I have a confession to make... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-08-16 14:21 +0100
      Re: I have a confession to make... Bart <bc@freeuk.com> - 2021-08-16 17:48 +0100
      Re: I have a confession to make... Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-09-06 06:30 -0700
        Re: I have a confession to make... David Brown <david.brown@hesbynett.no> - 2021-09-06 18:04 +0200

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