Re^2: NestedLoops (Algorithm::Loops) and Iterators

That's the same thing as:

$iter_prod = NestedLoops([
   sub { iter(qw(a b c) },
   sub { iter(qw(x y z) },
]);
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Wasn't the whole point to avoid flattening the iterator and to provide arbitrary nesting? Your solution flattens~~, and the depth is hardcoded as a sequence of calls to iter_prod~~.

Note: NestedLoops's iterator returns an array rather than an array ref.

Update: Your solution does support arbitrary depth:

my $iter = do { my $done = 0;  sub { $done++ ? undef : 1 } };
iter_prod($iter, ...) if ...;
iter_prod($iter, ...) if ...;
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With NestedLoops, you'd do:

my @iters;
push(@iters, ...) if ...;
push(@iters, ...) if ...;
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Re^3: NestedLoops (Algorithm::Loops) and Iterators by tmoertel (Chaplain) on Jul 27, 2005 at 04:06 UTC
Can you define what you mean by "flattening" and "arbitrary depth"? My understanding of these things does not lead me to see unresolved problems in the original post. (Also, I do not believe that the `NestedLoops` code you provided is equivalent to seq_prod.) In the OP's example while loop, the iterator returns scalar values. Thus I don't see how the seq_prod of such iterators could "flatten" the results: there are no intermediate array results to flatten. On the arbitrary depth issue, if you mean that iter_prod works only for a fixed number of iterators, that is not the case. You can pass it any number of iterators, and (as long as they are independent) it will yield an iterator over their Cartesian product. If you mean something else, say that the Cartesian product is not what is desired, we can derive a suitable combinator to replace seq_prod2 and use it (with reduce) to build the desired output iterator. For example, we could define a combinator that takes the product of two iterators when the second is generated dynamically from the output of the first. Cheers, Tom Tom Moertel : Blog / Talks / CPAN / LectroTest / PXSL / Coffee / Movie Rating Decoder	[reply]

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Re^3: NestedLoops (Algorithm::Loops) and Iterators
by tmoertel (Chaplain) on Jul 27, 2005 at 04:06 UTC

NestedLoops

seq_prod

In the OP's example while loop, the iterator returns scalar values. Thus I don't see how the seq_prod of such iterators could "flatten" the results: there are no intermediate array results to flatten.

On the arbitrary depth issue, if you mean that iter_prod works only for a fixed number of iterators, that is not the case. You can pass it any number of iterators, and (as long as they are independent) it will yield an iterator over their Cartesian product. If you mean something else, say that the Cartesian product is not what is desired, we can derive a suitable combinator to replace seq_prod2 and use it (with reduce) to build the desired output iterator. For example, we could define a combinator that takes the product of two iterators when the second is generated dynamically from the output of the first.

Cheers,
Tom

Tom Moertel : Blog / Talks / CPAN / LectroTest / PXSL / Coffee / Movie Rating Decoder

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