BSD-3-Clause licensed and maintained by Ashley Yakeley
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Used by 1 package in nightly-2018-04-04(full list with versions):

A witness is a value that witnesses some sort of constraint on some list of type variables. This library provides support for simple witnesses, that constrain a type variable to a single type, and equality witnesses, that constrain two type variables to be the same type. It also provides classes for representatives, which are values that represent types. See the paper Witnesses and Open Witnesses (http://semantic.org/stuff/Open-Witnesses.pdf).