On 1 October 2013 21:22, Chris <wend...@tcd.ie> wrote:
> Just a short question. Usually goto statements are frowned upon as being
> bad programming style (in textbooks at least). D has it (thankfully) and
> I've used it, albeit sparingly. Sometimes goto is simply the best and most
> efficient solution within a code block (to avoid code duplication,
> unnecessary checks or redirecting to yet another function blah blah). Is it
> ok or even necessary to use goto in D? Or does the compiler recognize
> _obvious_ cases and generate code accordingly? For example would it turn
> something like this
>
> // ...
> if (word.length == 1) {
> // format output
> return output;
> } else if (word.length > 1) {
> // do some additional processing
> // format output
> return output;
> }
>
> into
>
> // ...
> if (word.length == 1) goto FormatOutput;
>
> // if word.length > 1, some extra work has to be done
> // initialize some variables, parse, do some processing etc.
>
> FormatOutput:
> // .....
>
> return output;
>
Well, obviously that should be rewritten:
if (word.length > 1)
{
// additional processing
}
// format output
return output;
Note: there's an un-handled case in your example, but I'll ignore that.
Anyway, goto is supported. Walter likes it. I use it from time to time.
I'd say 90% of the time I find goto useful is when I need to bail from
nested loops. I've often wondered if something like break(2) would be a
more elegant solution to the breaking out of nested loops problem.
But in direct answer to your question, I think you'll find modern
optimisers are smart enough to make the optimisation you are looking for. I
haven't tested that precise case, but I've definitely expected the
optimiser to do the right thing in similar cases, and it does. I rarely
write code that requires me to have faith in any optimiser though.
