F

F is a pure functional concatenative language originally designed as an extension of False. F contains the list-operations of K3 and the dip combinator of Joy. Floating-point and symbolic datatypes are supported. One-time assignment is enforced in syntax. A theory of function-valence and -charge is outlined. F also contains a general continuation primitive $, and the pattern sublanguage of XY. G is a variant of F in which the K3 adverbs are implemented as primitives.

For more information:

http://nsl.com/k/f/f.htm