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copied!<p>Disclaimer: I don't have a machine with the current F# installed, so I can't test my code. Basically, though, if you steal <code>sequence</code> from Haskell, you can write your program as</p> <pre><code>let cartesian = sequence >> List.map product </code></pre> <p>and run it as</p> <pre><code>cartesian [[1..99]; [1..99]] </code></pre> <p>Here's how to write <code>sequence</code>. It's a generalised version of the sequence expression you wrote. It just handles an unlimited number of lists: <code>{ for x in xs do for y in ys do for z in zs ... yield [x;y;z;...] }</code>.</p> <pre><code>let rec sequence = function | [] -> Seq.singleton [] | (l::ls) -> seq { for x in l do for xs in sequence ls do yield (x::xs) } // also you'll need product to do the multiplication let product = Seq.fold_left1 ( * ) </code></pre> <p>Then you can write your program as</p> <pre><code>let cartesian xs ys = [xs; ys] |> sequence |> List.map product // ... or one-argument, point-free style: let cartesian' = sequence >> Seq.map product </code></pre> <p>You might have to change some <code>Seq</code>s to <code>List</code>s.</p> <p>However, the number of people who can guess the meaning of your non-general list comprehension is probably a lot more than will recognise the name <code>sequence</code>, so you're probably better off with the list comprehension. <code>sequence</code> comes in handy any time you want to run a whole list of computation expressions, though.</p>

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