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Unison | A friendly, statically-typed, functional programming language from the future · Unison programming language (www.unison-lang.org)
submitted 2 years ago by to c/programming@programming.dev
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A friendly programming language from the future.

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[–] 2 points 2 years ago (2 children)

I would even have said that both throwing and catching should be pure, just like returning an error value/handling should be pure, but the reason for the throw/returning error itself is impure. Like if you throw and ioerror it's only after doing the impure io call, and the rest of the error reporting/handling itself can be pure.

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  • [–] 1 point 2 years ago

    Pure functions should be referentially transparent; you should be able to replace them with whatever value they evaluate to without changing the semantics of your code.

    Throwing is referentially impure: what value do you get from calling x => throw new RuntimeException()?

    Instead, functional languages prefer to return a tagged union of the value or the error.

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