Your inerrant holiness who represents all of us!

> Indeed, whatever alternative mechanism is used, in whatever language, it will always be more costly than the natural return chain. The stack still has to be unwound

> Just as the exception mechanism in C++ (or structured exceptions in MSC), are a magnitude or more expensive because they have to search back up the stack looking for stack frames interpreting them as they go; so the goto that underlies such mechanisms in Perl has to go through an equally convoluted process to find a label at the appropriate scope.

Some heretics didn't fully trust you and tried to measure a time penalty for die or goto.

Look what they have done!

Timing for 1000000 recursions:
    Mode: return takes sec: 5.55880403518677
    Mode: goto takes sec: 4.51015114784241
    Mode: die takes sec: 1.70386385917664

[download]

use Time::HiRes qw/time/;

no warnings 'recursion';


our $mode;

sub rec {
  my $i=shift;
  $i--;
  if ($i<0) {
    return  if $mode eq "return";
    goto OUT if $mode eq "goto";
    die "finished" if $mode eq "die";
  }
  rec($i)
}

$|=1;

my $recs=1000000;

print "Timing for $recs recursions:\n" ;

for $mode (qw/return goto die/) {
  print "\tMode: $mode takes sec: ";
  my $start=time;
  eval {
    rec($recs);
  };
 OUT:
  # print $@ if $@;
  print time-$start,"\n";
}

[download]

Please prove them wrong!

May those heathens all burn in hell (...or emacs)!

Cheers Rolf

( addicted to the Perl Programming Language)

In reply to Re^4: Continuations in Perl - Returning to an arbitrary level up the call stack by LanX
in thread Continuations in Perl - Returning to an arbitrary level up the call stack by unlinker

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