LISP and Symbolic Computation, 8(4)293-341
State in HaskellJohn Launchbury, Oregon Graduate Institute, PO Box 91000, Portland, OR 97291-1000
Simon L. Peyton Jones, University of Glasgow, G12 8QQ, Scotland
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Abstract: Some algorithms make critical internal use of
updatable state, even though their external specification is purely
functional. Based on earlier work on monads, we present a way of
securely encapsulating stateful computations that manipulate multiple,
named, mutable objects, in the context of a non-strict,
purely-functional language. The security of the encapsulation is
assured by the type system, using parametricity. The same framework is
also used to handle input/output operations (state changes on the
external world) and calls to C. Keywords: functional programming, side-effects, types, input-output |
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