The Kent Recursive Calculator (KRC)

The Kent Recursive Calculator (KRC) was a lazy, untyped, purely functional programming language developed by David Turner at the University of Kent (1979-1981).

The KRC was an immediate successor to SASL. Moreover, it was a direct precursor to Miranda, and consequently influenced the development of Haskell.

In fact, KRC looks eerily similar to Haskell: see e.g. the 1981 prelude (not copied here due to copyright restrictions).

The original paper on the KRC Turner 1981 contains an interesting diss on LISP:

Perhaps I should explain why I don’t teach my students LISP (McCarthy et al. 1962) which is still the language most people first think of when functional programming is mentioned. There are two reasons — the first is that the syntax of LISP is so clumsy that it constitutes a real obstacle to comprehension. Fig. 2 illustrates this with a definition of Ackermann’s function in LISP — note that there are eighteen pairs of parentheses! — and for contrast a definition of the same function in KRC, which looks more like a piece of ordinary mathematics. The second and more serious reason is that the semantics of LISP are rather complicated and include a number of features which could in no sense be regarded as functional. The net effect, at least in my experience, is that as a vehicle for teaching people about functional programming, LISP is apt to cause more confusion than enlightenment and I prefer to avoid using it.

External links

The open source interpreter of KRC is maintained on codeberg
A large example of KRC (and Miranda and Haskell) programming is the infinite-precision math library

References

The Wikipedia page on the KRC.
A page by David Turner on the KRC, including the sources of original implementation, as well as some bibliographic references.
The original paper on the KRC:

Turner, D. A. 1982. ‘Recursion Equations as a Programming Language’. In Functional Programming and Its Applications: An Advanced Course, edited by J. Darlington, P. Henderson, and D. A. Turner, 1–29. Cambridge University Press.

@incollection{darlington_recursion_1982,
	title = {Recursion {Equations} as a {Programming} {Language}},
	booktitle = {Functional programming and its applications: an advanced course},
	publisher = {Cambridge University Press},
	author = {Turner, D. A.},
	editor = {Darlington, J. and Henderson, P. and Turner, D. A.},
	year = {1982},
	pages = {1--29},
}

It has been reprinted as

Turner, D. A. 2016. ‘Recursion Equations as a Programming Language’. In A List of Successes That Can Change the World, edited by Sam Lindley, Conor McBride, Phil Trinder, and Don Sannella, 9600:459–78. Lecture Notes in Computer Science. Cham: Springer International Publishing. https://doi.org/10.1007/978-3-319-30936-1_24. pdf

@incollection{turner_2016,
	address = {Cham},
	series = {Lecture {Notes} in {Computer} {Science}},
	title = {Recursion {Equations} as a {Programming} {Language}},
	volume = {9600},
	booktitle = {A {List} of {Successes} {That} {Can} {Change} the {World}},
	publisher = {Springer International Publishing},
	author = {Turner, D. A.},
	editor = {Lindley, Sam and McBride, Conor and Trinder, Phil and Sannella, Don},
	year = {2016},
	doi = {10.1007/978-3-319-30936-1_24},
	pages = {459--478}
}