Re: No Go To's Forever!

[Robert Dewar <robert_dewar@my-deja.com>]

In article
<Pine.SOL.4.21.0003212347450.15450-100000@fraggel81.mdstud.chalm
ers.se>,
  =?ISO-8859-1?Q?Tim_Gahnstr=F6m?= <md9tim@mdstud.chalmers.se>
wrote:

> I realize everything is posible to do without gotos
> but I canot figure out why it is so horible.
> Please enlighten me.
> Is goto statments particular slow?
>
> Tim

Gotos often make simple code hard to read. Your example is
a good one!

   <<start>>
   while bool loop
     skipline(infile);
     look_ahead(in_file,ch,bool);
   end loop;

   if ch=' ' then
     while ch=' ' loop
       get(infile,ch);
       look_ahead(in_file,ch,bool);
     end loop;
     goto start;
   end if;

The following is preferable in every way. It makes the exit
condition from the outer loop far clearer (not to mention making
it clearer that there *is* an outer loop!

    loop
      while bool loop
        skipline(infile);
        look_ahead(in_file,ch,bool);
      end loop;

      exit when ch /= ' ';

      while ch=' ' loop
        get(infile,ch);
        look_ahead(in_file,ch,bool);
      end loop;
    end loop;

It is shorter and clearer.

<<Is goto statments particular slow?>>

No, the concern is not for efficiency at all!

There are (rare) cases where gotos are appropriate, but they
are few and far between, and your example is a good one showing
why gotos should not generally be used.

In fact gotos are so often misused that some people go to the
extreme of saying they should never ever be used. This approach
is excessive, but has the advantage of completely eliminating
the kind of misuse you illustrate in your example.


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