let floating


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



1. An e-mail message containing live data intended to do nefarious things to the recipient's computer or terminal. It is possible, for example, to send letterbombs that will lock up some specific kinds of terminals when they are viewed, so thoroughly that the user must turn the terminal off to unwedge it. Under Unix, a letterbomb can also try to get part of its contents interpreted as a shell command. The results of this could range from silly to tragic.

See also Trojan horse; compare nastygram, talk bomb.

2. Loosely, a mailbomb.

[Jargon File]

Last updated: 1998-01-16

Nearby terms:

less thanLessTiflet floatingletterbomblevel 1 cachelevel 2 cache

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