🏔 Eva Lang

Eva is a dialect of lisp implemented in JavaScript. This project was build with the purpose of understanding how an interpreter for a dialect of lisp works. The current implementation supports variables, loops, conditionals, fisrt class functions, lambda functions, closures, classes and modules.

Usage

1. Clone the repository

2. Run the eva 'binary' with the '-e' flag to execute code passed on the command line or '-f' to execute an eva file.

Execute an eva source code file: ./bin/eva -f fib.eva

Execute a simple expression: ./bin/eva -e '(var x 10) (print x)'

Example Eva Code

Simple Arithmetic

(+ (* 3 2) 5) => 11

(- (- (* 5 3) 2) 3) => 10

Variables

(var x 5)

(print x) => 5

Conditionals

(var value (- 10))

(if (< value 0)
  (- value)
  (value)
)

Switch

(begin
  (var x 10)
  (switch ((= x 10) 100)
          ((> x 10) 200)
          (else     300)
  )
)

For Loops

(var result 0)

(for
  (var x 10)
  (> x 0)
  (-- x)
  (
    (++ result)
  )
)

result

Functions

(def square (x)
  (* x x)
)

(square 5)

Closures and First Class Functions

(var value 100)

(def calc (x y)
  (begin
    (var z (+ x y))

    (def inner (foo)
      (+ (+ foo z) value)
    )

    inner
  )
)

(var fn (calc 10 20))

(fn 30)

Lambda Functions

(def onClick (callback)
  (begin
    (var x 10)
    (var y 20)
    (callback (+ x y))
  )
)

(onClick (lambda (data) (* data 10)))

Classes and Inheritance

(class Point null
  (begin

    (def constructor (this x y)
      (begin
        (set (prop this x) x)
        (set (prop this y) y)
      )
    )

    (def calc (this)
      (begin
        (+ (prop this x) (prop this y))
      )
    )

  )
)

(class Point3D Point
  (begin

    (def constructor (this x y z)
      (begin
        ((prop (super Point3D) constructor) this x y)
        (set (prop this z) z)
      )
    )

    (def calc (this)
      (+ ((prop (super Point3D) calc) this) (prop this z))
    )

  )
)

(var p (new Point3D 10 20 30))
((prop p calc) p)