21-letter words containing w, a, f
- traffic control tower — an elevated structure for the visual observation and control of the air and ground traffic at an airport
- venus's flower basket — a glass sponge of the genus Euplectella, inhabiting deep waters off the Philippines and Japan, having a cylindrical skeleton formed of an intricate latticework of siliceous spicules.
- warm silence software — A small company run by(?) Robin Watts, producing software for the Acorn Archimedes.
- water of constitution — water present in a molecule that cannot be removed without disrupting the molecule.
- weak head normal form — (reduction, theory) (WHNF) A lambda expression is in weak head normal form (WHNF) if it is a head normal form (HNF) or any lambda abstraction. I.e. the top level is not a redex. The term was coined by Simon Peyton Jones to make explicit the difference between head normal form (HNF) and what graph reduction systems produce in practice. A lambda abstraction with a reducible body, e.g. \ x . ((\ y . y+x) 2) is in WHNF but not HNF. To reduce this expression to HNF would require reduction of the lambda body: (\ y . y+x) 2 --> 2+x Reduction to WHNF avoids the name capture problem with its need for alpha conversion of an inner lambda abstraction and so is preferred in practical graph reduction systems. The same principle is often used in strict languages such as Scheme to provide call-by-name evaluation by wrapping an expression in a lambda abstraction with no arguments: D = delay E = \ () . E The value of the expression is obtained by applying it to the empty argument list:
- what the future holds — If you wonder what the future holds, you wonder what will happen in the future.
- whip-and-tongue graft — a graft prepared by cutting both the scion and the stock in a sloping direction and inserting a tongue in the scion into a slit in the stock.
- wildlife photographer — someone that specializes in taking photographs of wild animals, especially in their natural habitats, and plants
- william of malmesbury — William of, William of Malmesbury.
- without qualification — If something is stated or accepted without qualification, it is stated or accepted as it is, without the need for any changes.
- writ of habeas corpus — law: petition for hearing