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POMultiple Exits From F# Function
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copied!<p>I could do this easily in C++ (note: I didn't test this for correctness--it's only to illustrate what I'm trying to do):</p> <pre><code> const int BadParam = -1; const int Success = 0; int MyFunc(int param) { if(param < 0) { return BadParam; } //normal processing return Success; } </code></pre> <p>But I cannot figure out how to exit a routine early in F#. What I want to do is to exit the function on a bad input but continue if the input is ok. Am I missing some fundamental property of F# or am I approaching the problem in the wrong way since I'm just learning FP? Is a <em>failwith</em> my only option here?</p> <p>This is what I've got so far and it compiles ok:</p> <pre><code> #light module test1 (* Define how many arguments we're expecting *) let maxArgs = 2;; (* The indices of the various arguments on the command line *) type ProgArguments = | SearchString = 0 | FileSpec = 1;; (* Various errorlevels which the app can return and what they indicate *) type ProgReturn = | Success = 0 | WrongNumberOfArgumentsPassed = 1;; [<EntryPoint>] let main (args:string[]) = printfn "args.Length is %d" args.Length let ProgExitCode = if args.Length <> maxArgs then printfn "Two arguments must be passed" int ProgReturn.WrongNumberOfArgumentsPassed (* Want to exit "main" here but how? *) else int ProgReturn.Success let searchstring, filespec = args.[int ProgArguments.SearchString],args.[int ProgArguments.FileSpec]; printfn "searchstring is %s" searchstring printfn "filespec is %s" filespec ProgExitCode;; </code></pre> <p>Is there an FP way of dealing with this sort of thing? </p>

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