PopovMP / schemy

A Scheme language interpreter in JavaScript.

Minimal Scheme

Use on server

npm install
npm run build
npm run test

Execute code:

const Schemy = require("../bin/schemy.js").Schemy
const schemy = new Schemy()

const code = `(define a 5)
              (+ a a)`

const res = schemy.evaluate(code)
console.log(res) // -> 10

Use in browser

<script src="js/schemy.js"></script>
<script>
	const schemy = new Schemy()

	const code = `(define a 5)
	              (+ a a)`

	const res = schemy.evaluate(code)
	console.log(res) // -> 10
</script>

Forms

Quote

(quote <expression>)
'<expression>

Definition

(define <symbol> <expression>)

Lambda

Accepts zero or more bound parameters. Evaluates and returns the value of the body expression.

(lambda (p0 p1 ... pn)
  <expression>)

Condition

Contains three expressions

(if <expression>  ; test expression
    <expression>  ; then expression
    <expression>) ; else expression

Block of code

Evaluates all expressions in order. Returns the value of the last expression

(begin <expression 1>
       <expression 2>
       ...
       <expression n>)

Primitive data types

###Symbol

'symbol

Number

1 3.14 +42.5 -22.5

Lambda

(lambda () expr)
(lambda (p1 p2 ... pn) expr)

List

'()
(list)

'(1 2 3)
(list 1 2 3)
(cons 1 (cons 2 (cons 3 '())))

String

"Hello world!"

Standard procedures

Confirm data type:

(number?  e)
(symbol?  e)

Comparison:

(eq? e1 e2) ; Returns 1 or '()

Lists:

(cons e1 e2)
(car e)
(cdr e)

Output:

(display e)
(newline)

Math:

(+  e1 e2)
(-  e1 e2)
(*  e1 e2)
(/  e1 e2)

(modulo e)
(round  e)
(floor  e)

(=  e1 e2)
(>  e1 e2)
(>= e1 e2)
(<  e1 e2)
(<= e1 e2)