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8 lines
511 B
8 lines
511 B
7 years ago
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# Exercises: Parametricity
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1. As said this is impossible. A function which takes any type and returns that same type can't be anything else. As soon as you choose something else, you pose limitations on the type. E.g. `square x = x * x` requires that `x` can be applied to `(*)`, which means it has to be of type `Num` at least.\
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2. The only possibilies are to return either the first or the second argument.
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1. `fst' a1 a2 = a1`
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2. `snd' a1 a2 = a2`
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3. Here there is only one possiblity: `snd'' a b = b`.
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