Re^4: Next Language to Learn

[LanX]

Sorry I didn't intend to criticize you, it's only my personal impression after a long indoctrination...

Me, I'm rather interested to realize different paradigms in Perl, maybe by extending the language.

(even if it provokes the resistance of local clerics... ;)

[rovf]

Sorry I didn't intend to criticize you

I didn't interpret it that way ;-)

I'm rather interested to realize different paradigms in Perl, maybe by extending the language.

For instance it would be interesting to see, how easy/clumsy it is to retrofit lazy evaluation into Perl.

With enough pertinacity, every language can be made to look like LISP :-D

[LanX]

> 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.

I'm not fluent in Haskell, so gimme an example and I'll see what's possible.

> With enough pertinacity, every language can be made to look like LISP :-D

Well, unfortunately it's not trivial to realize LISPish macros in Perl 5, otherwise most language extensions I can think of would be easily possible.

Compare Re^2: Dumping variables but DRY and simple for a use case for a macro.

[rovf]

> 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))
}

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;
  @_
}

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...