> For instance it would be interesting to see, how easy/clumsy it is to retrofit lazy evaluation into Perl. E.g.you can tie an iterator to a variable. ... gimme an example and I'll see what's possible.
Good point.

For example, we have a function which generates the list of all even numbers, i.e. 

sub list_all_even {
   _list_all_even_from(0)
}
sub _list_all_even_from {
   my $from=shift;
   ($from, _list_all_even_from($from+2))
}

[download]
and a function which returns the first n elements from a list: 
sub head {
  my ($n,@list)=@_;
  $n ? ($list[0],head($n-1,butfirst(@list))) : ()
}
sub butfirst {
  shift;
  @_
}

[download]

Calling head(5,list_all_even) should return the first even numbers, but in the implementation I gave, list_all_even would, of course, loop forever. Under lazy evaluation, list_all_even would only produces those values which are actually needed, so maybe your general idea of using an operator would lead in the right direction...
-- 
Ronald Fischer <ynnor@mm.st>

In reply to Re^7: Next Language to Learn by rovf
in thread Next Language to Learn by Anonymous Monk

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