Related:

• There is an infinite number of describable functions, which are not effectively computable.
  N. Jones - "Computability Theory" Note: This contradicts the oft stated maxim "If a function can be defined, it can be programmed"....
• Mathematicians do it with odd functions.
• Use library functions.
• ap door n. (alt. `trapdoor') 1. Syn. back door -- a Bad Thing.
  2. [techspeak] A `trap-door function' is one which is easy to compute but very difficult to compute the inverse of....
• ap door: alt. `trapdoor' n. 1. Syn. {back door} --- a {Bad Thing}.
  2. [techspeak] A `trap-door function' is one which is easy to compute but very difficult to compute the inverse of....
• oggle: vt. To change a {bit} from whatever state it is in to the other state
  o change from 1 to 0 or from 0 to 1. This comes from `toggle switches', such as standard light switches, though the word `toggle' actually refers to the mechanism that keeps the switch in the position to which it is flipped rather than to the fact that the switch has two positions....
• oggle vt. To change a bit from whatever state it is in to the other state
  o change from 1 to 0 or from 0 to 1. This comes from `toggle switches', such as standard light switches, though the word `toggle' actually refers to the mechanism that keeps the switch in the position to which it is flipped rather than to the fact that the switch has two positions....
• LISP hackers do it in lambda functions.