loom

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// Module interface declaration
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interface Factorial : immutable {
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    func factorial(int n) -> int f
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    :    pure,
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         pre    (n > 0),
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         post   (f > 0 && f < 1000000)
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}
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// Defining module functions
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func factorial(int n)
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->   int
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{
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    return (n == 1) ? 1 : n*factorial(n-1)
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}
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