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.

To define a list in F, you use the bracket operator. Arithmetic operators are one character, and usually the character you'd expect. There are logical operators that return booleans such as equal (=) and more (>). There is also minimum which is &. Among these there is also match (~) which checks if the values of two arrays are the same.

The next combinator is shape (#) which returns the size(s) of multidimensional and single-dimensional arrays alike. Then there is reverse (|) which reverses the values of an array. Then where (@) which checks for indices that are true if interpreted as booleans.

For more information:

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