In Perl "goto &NAME" is a way to implement tail calls, and is often discussed in the archives

But there are also many complaints that in case of a recursive call the tail call is not optimized (e.g. see Why is goto &sub slow?).

Now I'm wondering if syntactic sugar using redo in a (pseudo loop) block doesn't exactly do the trick but in a readable way ...?

In other words is there any effective difference between

sub f1 { ++$a < $_[0] ? goto &f1 : return $a}

and

sub f2 {{ ++$a < $_[0] ? redo : return $a }}

except that the latter is about 8 times faster?

(Of course one might need a label if the redo is in a nested loop construct)

BTW:the algorithm isn't spectacular it just recursively increments $a till a upper bound is reached:

  DB<103> sub f1 { ++$a < $_[0] ? goto &f1 : return $a}
 
  DB<104> $a=0; print f1(1000)
1000
  DB<105> print $a
1000

[download]

If you want fancier applications of this pattern please refer to the links I gave.

Cheers Rolf

PS: If you wanna ask why not directly relying on iterative code, please read Re: Re: Re: Re: Iterative vs Recursive Processes.

In reply to Syntactic sugar for tail call optimizations by LanX

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