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copied!<p><code>collect</code> is the F# equivalent of SelectMany however it doesn't provide all the overloads. Here's how to make the one you referenced.</p> <pre><code>let selectMany (ab:'a -> 'b seq) (abc:'a -> 'b -> 'c) input = input |> Seq.collect (fun a -> ab a |> Seq.map (fun b -> abc a b)) // gives // val selectMany : ('a -> seq<'b>) -> ('a -> 'b -> 'c) -> seq<'a> -> seq<'c> </code></pre> <p>I believe F# doesn't provide all the SelectMany overloads because they would add noise to the library. Here's all four overloads to <a href="http://msdn.microsoft.com/en-us/library/bb345618(v=VS.95).aspx" rel="nofollow noreferrer">SelectMany</a> in Microsoft Naming.</p> <pre><code>let selectMany (source : 'TSource seq) (selector : 'TSource -> 'TResult seq) = source |> Seq.collect selector let selectMany (source : 'TSource seq) (selector : 'TSource -> int -> 'TResult seq) = source |> Seq.mapi (fun n s -> selector s n) |> Seq.concat let selectMany (source : 'TSource) (collectionSelector : 'TSource -> 'TCollection seq) (resultSelector : 'TSource -> 'TCollection -> 'TResult) = source |> Seq.collect (fun sourceItem -> collectionSelector sourceItem |> Seq.map (fun collection -> resultSelector sourceItem collection)) let selectMany (source : 'TSource) (collectionSelector : 'TSource -> int -> 'TCollection seq) (resultSelector : 'TSource -> 'TCollection -> 'TResult) = source |> Seq.mapi (fun n sourceItem -> collectionSelector sourceItem n |> Seq.map (fun collection -> resultSelector sourceItem collection)) |> Seq.concat </code></pre> <p>"F# List operations are more powerful than LINQ..." While seq / list operations are great some real "F# power" comes from <a href="http://blogs.msdn.com/b/chrsmith/archive/2008/06/14/function-composition.aspx" rel="nofollow noreferrer">Function Composition</a> and <a href="https://stackoverflow.com/questions/8448/f-curried-function">Currying</a>.</p> <pre><code>// function composition let collect selector = Seq.map selector >> Seq.concat </code></pre>

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