[Agda] Parametricity is inconsistent with classical logic

Jean-Philippe Bernardy bernardy at chalmers.se
Wed May 9 09:44:23 CEST 2012

> What exactly is parametricity? Could you write it in one line of Agda? I am unable to get consistent answers from Google.

I humbly recommend reading sec. II B and II C of this paper:


In sum, parametricity imposes that terms satisfy the constraints
imposed by the type-system, expressed as logical relations. It is
called "parametricity" because the types of types are usually
abstract, and in that case the condition imposes parametric behaviour
to polymorphic functions.


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