Minimal Scheme Interpreter

Minimal Scheme interpreter in JavaScript

Based on (metacircular Scheme) evaluator in Structure and Interpretation of Computer Programs (SICP)

what it is

an interpreter for a lexically-scoped, minimalist-designed, dialect of lisp

it is initially nowhere close to R5RS- or R6RS-complient

the following operands (in alphabetical order) are implemented

• begin
• cond
• define (the minimalist one for now)
• if
• lambda
• quote
• set!

at the momemnt you need to implement cons, car and cdr yourself using lambda. :)

how it works

It basically works by doing two things ->

1. to evaluate a combination (a compound expression other than a special form), it evaluates the subexpressions and then applies the value of the operator subexpression to the values of the operand subexpressions.
2. to apply a compound procedure to a set of arguments, it evaluates the body of the procedure in a new environment. To construct this environment, it extends the environment part of the procedure object by a frame in which the formal parameters of the procedure are bound to the arguments to which the procedure is applied.

in-browser example (evaluates each keypress)

input:(define addFour (lambda (n) (+ 4 n)))
(addFour 3)

output: