Created
January 29, 2013 13:46
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Piping operators for operations that can fail
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| infix 1 |> !> !?> | |
| fun v |> f = f v | |
| fun NONE !> _ = NONE | |
| | (SOME v) !> f = f v | |
| fun NONE !?> _ = NONE | |
| | (SOME v) !?> f = SOME (f v) | |
| (* Example usage: *) | |
| fun isqrt n = | |
| let val r = n |> real |> Math.sqrt |> round | |
| in if r * r = n then SOME r | |
| else NONE | |
| end; | |
| "123s" |> Int.fromString !?> (fn i => i * i) !> isqrt; (* = SOME 123 *) | |
| "lulz" |> Int.fromString !?> (fn i => i * i) !> isqrt; (* = NONE *) |
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