ORy> A function with no free variables. A term is either a constant, a variable OR of the fORm A B denoting the application of term A (a function of one argument) to term B. Juxtaposition associates to the left in the absence of parentheses. All combinatORs can be defined from two basic combinatORs - S and K. These two and a third, I, are defined thus: S f g x = f x (g x) K x y = x I x = x = S K K x There is a simple translation between combinatORy logic and lambda-calculus. The size of equivalent expressions in the two languages are of the same ORder. Other combinatORs were added by David Turner in 1979 when he used combinatORs to implement SASL: B f g x = f (g x) C f g x = f x g S' c f g x = c (f x) (g x) B* c f g x = c (f (g x)) C' c f g x = c (f x) g See fixed point combinatOR, curried function, supercombinatORs. (2002-11-03)