Constraints that any type, resp. no type fulfills

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Stackage Nightly 2019-07-18:
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GPL-3.0-only licensed by Justus Sagemüller
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Since GHC 7.4, constraints are first-class: we have the constraint kind, and thus type-classes have a kind such as * -> Constraint.

These can be used as parameters to data types. They also can be combined quite nicely,

type NewConstraint a = (Constraint1 a, Constraint2 a)

however you always need to start with a plain old type class when building constraints.

This library provides a type class that is not really a constraint at all, so you can "start from zero" with building up a custom constraint. Also its opposite (a constraint that no type can ever fulfill).

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Used by 1 package in nightly-2019-07-11(full list with versions):
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