Kihi is a concatenative, compositional, functional programming language with a minimal core of only six operations.
The Practice of a Compositional Functional Programming Language. Timothy Jones, Michael Homer. In APLAS, 2018.
Function composition is a very natural operation, but most
language paradigms provide poor support for it. Without linguistic
support programmers must work around or manually implement what
would be simple compositions. The Kihi language uses only
composition, makes all state visible, and reduces to just six core
operations. Kihi programs are easily stepped by textual reduction
but provide a foundation for compositional design and analysis.
Michael Homer — 2019