21-letter words containing k, h
- to take the long view — If you take the long view, you consider what is likely to happen in the future over a long period, rather than thinking only about things that are going to happen soon.
- to think better of it — If you intend to do something and then think better of it, you decide not to do it because you realize it would not be sensible.
- 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.