let floating

(programming)   A program transformation used in functional programming to implement full laziness. E.g. the function

	f x = x + sqrt 4
can be expressed as

	f x = let t = sqrt 4 in x + t
but note that t does not depend on the argument x so we can automatically transform this to

	t = sqrt 4
	f x = x + t
Making t into a global constant which need only be evaluated at most once, rather than every time f is called. The general idea is to float each subexpression as far out (toward the top level) as possible to maximise sharing.

Last updated: 1997-07-09


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