21-letter words containing a, l, k
- tuple space smalltalk — ["Using Tuple Space Communication in Distributed Object-Oriented Languages", S. Matsuoka et al, SIGPLAN Notices 23(11):276-284 (Nov 1988)].
- universal disk format — (storage, standard) (UDF) A CD-ROM file system standard that is required for DVD ROMs. UDF is the OSTA's replacement for the ISO 9660 file system used on CD-ROMs, but will be mostly used on DVD. DVD multimedia disks use UDF to contain MPEG audio and video streams. To read DVDs you need a DVD drive, the kernel driver for the drive, MPEG video support, and a UDF driver. DVDs containing both UDF filesystems and ISO 9660 filesystems can be read without UDF support. UDF can also be used by CD-R and CD-RW recorders in packet writing mode.
- 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.
- venus's looking glass — a purple-flowered campanulaceous plant, Legousia hybrida, of Europe, W Asia, and N Africa
- vladivostok agreement — a preliminary arms control accord concluded by Soviet leader Leonid Brezhnev and U.S. President Gerald Ford in Vladivostok, U.S.S.R., in December 1974.
- 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:
- whistling in the dark — If you say that someone is whistling in the dark, you mean that they are trying to remain brave and convince themselves that the situation is not as bad as it seems.
- white-knuckle paddler — an inexpert and timid canoeist.