value restriction

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value restriction

Wikipedia

Noun

value restriction (uncountable)

1. (computer science, type theory) In a functional language, inference of a polymorphic type only for syntactic values (values that can be evaluated at compile time) to ensure that a program is type-safe.
   • 2004, Jacques Garrigue, Relaxing the Value Restriction:

     A typical example is an expression returning always the empty list. It should be given the polymorphic type α list, but this is not possible under the value restriction if the expression has to be evaluated.

   • 2007, Geoffrey Smith, Notes on SML97's Value Restriction‎:

     It has been found empirically that eta expansion usually suffices for dealing with the value restriction.