peach-lang

peach

A statically typed functional language.

fib =
  0 => 1
  1 => 1
  x => (+ (fib (- x 1)) (fib (- x 2)))

(map fib [0 1 2 3 4 5 6 7 8 9 10])
# [ 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 ]

Syntax

Peach is inspired by JavaScript, Elm, Clojure and @bodil's BODOL, which I learned about from this awesome talk.

# assignment
x = 2 # 2

# equality
(== x 2) # true

# maths and stuff
(* x 2) # 4

# conditionals
if ((< x 10))
  `little`
else if ((< x 20))
  `medium`
else
  `large`

# functions
double = (x => (* x 2))
(map x (x => (pow x 2))) # [2 4 8 16]

# currying
double-all = (map double)
(double-all [1 2 3 4]) # (2 4 6 8)

# pattern matching
(fn fib
  0 => 1
  1 => 1
  x => (+ (fib x - 2) (fib x - 1))
)

(fn starts-with-one
  [1|_] => true
  _  => false
)

# tail call optimisation
# n: the accumulating factorial
# x: a decrementing iteration count
factorial =
  (n, 1) => n
  (n, x) => (factorial (* n x) (- x 1))

(factorial 1 32768) # Infinity, because JavaScript. Better than a stack overflow!

Semantics

• Static typing (with Damas-Hindley-Milner type inference)
• Pure functions
• Everything is an expression
• Immutability
• Strict evaluation
• Currying

Features

• Minimal syntax
• A tree-based JavaScript interpreter
• REPL
• Proper tails calls

Plans

Coming soon:

• Type hint syntax
• More stdlib
• Algebraic data types

And then:

• JavaScript interop
• JavaScript code generation
• Lazy sequences
• IO

One day:

• Efficient bytecode interpreter
• Interactive debugger
• Immutable data structures with structural sharing
• Self-hosting

Develop

Use Node 6+.

npm install
npm test