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

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

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