call-by-need

reduction A reduction strategy which delays evaluation of

function arguments until they are needed because they are

arguments to a primitive function or a conditional.

Call-by-need is one part of lazy evaluation.

The term first appears in Chris Wadsworth's thesis "Semantics

and Pragmatics of the Lambda calculus" (Oxford, 1971, p. 183).

It was used later, by J. Vuillemin in his thesis (Stanford,

1973).

(1995-05-27)