CoSy

CoSy is a stack-based APL influenced language written by Bob Armstrong of Coherent Systems Inc. CoSy is implemented as a vocabulary of defined words that extends Reva Forth to provide array capabilities. CoSy has been re-implemented twice. The original implementation was in flat APL, the second in K, and finally the current implementation in Forth.

Features
CoSy has many major departures from the APL tradition: Most notably, it uses keywords for primitive functions.

All arrays in CoSy are simple lists. This makes it comparable to K and RAD. Similar to those languages, it also allows usage of functions as data using Forth's quoting.