Lispkit Lisp is a
lexically scoped,
purely functional subset of
Lisp
A lisp is a speech impairment in which a person misarticulates sibilants (, , , , , , , ). These misarticulations often result in unclear speech.
Types
* A frontal lisp occurs when the tongue is placed anterior to the target. Interdental lisping ...
("Pure Lisp") developed as a testbed for
functional programming concepts. It was first used for early experimentation with
lazy evaluation. An
SECD machine-based implementation written in an
ALGOL variant was published by the developer Peter Henderson in 1980.
The
compiler and
virtual machine are highly
portable and as a result have been implemented on many machines.
Base language
The base language provides the following functions only but extensions are discussed in Henderson's book
for the explicit support of lazy evaluation and
non-deterministic programming
A nondeterministic programming language is a language which can specify, at certain points in the program (called "choice points"), various alternatives for program flow. Unlike an if-then statement, the method of choice between these alternativ ...
.
;atom: given an expression returns True if its value is atomic; False if not.
;add: given two expressions returns the sum of their numeric values.
;car: given an expression whose value is a pair, returns the pair's first value.
;cdr: given an expression whose value is a pair, returns the pair's second value.
;cons: given two expressions returns a value pair consisting of their values.
;div: given two expressions returns the quotient of their numeric values.
;eq: given two expressions returns True if their values are equal; False if not.
;if: given three expressions returns the value of the second if the value of the first is True, otherwise returns the value of the third.
;lambda: given an argument list and an expression, returns them as a function.
;let: given an expression with declarations (as named expressions visible in the expression) returns its value.
;letrec: like let, except the declared names are also visible in the declarations themselves.
;leq: given two expressions, returns True if the value of the first is numerically less than or equal to the value of the second; False if not.
;mod (or rem): given two expressions, returns the modulus (also known as the remainder) of their numeric values.
;mul: given two expressions, returns the product of their numeric values.
;quote: given an expression, returns that expression as a value.
;sub: given two expressions, returns the difference of their numeric values.
The functions, ''lambda'', ''let'', and ''letrec'', are similar but have subtle differences in the way that they treat named variables which make them useful in different ways. ''lambda'' defines and returns a function, ''let'' binds expressions to variable names, and ''letrec'' is essentially similar to ''let'' except it allows for the definition of
recursive functions and values, e.g., infinite series.
References
Further reading
*{{cite book , last1=Henderson , first1=Peter , last2=Jones , first2=Geraint A. , last3=Jones , first3=Simon B. , title=The LispKit Manual , year=1983 , publisher=University of Oxford Computing Lab, isbn=0-902928-18-X
External links
* The LispKit Manual
Volume 1Volume 2
Implementation of Lispkit
GNU Pascal LispKit port
Archive of old LispKit LISP code and files, plus C implementation of SECD machine
Paper about a LispKit LISP implementation in Java
an
Lisp programming language family