ntha

A tiny statically typed functional programming language. https://github.com/zjhmale/ntha

Latest on Hackage:0.1.3

This package is not currently in any snapshots. If you're interested in using it, we recommend adding it to Stackage Nightly. Doing so will make builds more reliable, and allow stackage.org to host generated Haddocks.

BSD3 licensed by zjhmale
Maintained by zjhmale@gmail.com

Ntha Programming Language

Build Status zjhmale Haskell Hackage Hackage-Deps

a tiny statically typed functional programming language.

Installation

  • brew install z3
  • cabal install ntha

Features

  • Global type inference with optional type annotations.
  • Lisp flavored syntax with Haskell like semantic inside.
  • Support basic types: Integer, Character, String, Boolean, Tuple, List and Record.
  • Support unicode keywords.
  • Support destructuring.
  • ADTs and pattern matching.
  • Haskell like type signature for type checking.
  • Refined types (still in early stage, just support basic arithmetic operations and propositinal logic, here is some examples), based on z3-encoding
  • Module system (still in early stage, lack of namespace control).
  • Support pattern matching on function parameters.
  • Lambdas and curried function by default.
  • Global and Local let binding.
  • Recursive functions.
  • If-then-else / Cond control flow.
  • Type alias.
  • Do notation.
  • Begin block.

Future Works

Screenshot

cleantha

Example

(type Name String)
(type Env [(Name . Expr)])

(data Op Add Sub Mul Div Less Iff)

(data Expr
  (Num Number)
  (Bool Boolean)
  (Var Name)
  (If Expr Expr Expr)
  (Let [Char] Expr Expr)
  (LetRec Name Expr Expr)
  (Lambda Name Expr)
  (Closure Expr Env)
  (App Expr Expr)
  (Binop Op (Expr . Expr)))

(let op-map {:add +
             :sub -
             :mul *
             :div /
             :less <
             :iff =})

(arith-eval : (α → (β → Z)) → ((α × β) → (Maybe Expr)))
(ƒ arith-eval [fn (v1 . v2)]
  (Just (Num (fn v1 v2))))

(logic-eval : (α → (β → B)) → ((α × β) → (Maybe Expr)))
(ƒ logic-eval [fn (v1 . v2)]
  (Just (Bool (fn v1 v2))))

(let eval-op
  (λ op v1 v2 ⇒
    (match (v1 . v2)
      (((Just (Num v1)) . (Just (Num v2))) ⇒
        (match op
          (Add ⇒ (arith-eval (:add op-map) (v1 . v2)))
          (Sub ⇒ (arith-eval (:sub op-map) (v1 . v2)))
          (Mul ⇒ (arith-eval (:mul op-map) (v1 . v2)))
          (Div ⇒ (arith-eval (:div op-map) (v1 . v2)))
          (Less ⇒ (logic-eval (:less op-map) (v1 . v2)))
          (Iff ⇒ (logic-eval (:iff op-map) (v1 . v2)))))
      (_ ⇒ Nothing))))

(eval : [(S × Expr)] → (Expr → (Maybe Expr)))
(ƒ eval [env expr]
  (match expr
    ((Num _) ⇒ (Just expr))
    ((Bool _) → (Just expr))
    ((Var x) ⇒ (do Maybe
                 (val ← (lookup x env))
                 (return val)))
    ((If condition consequent alternative) →
          (match (eval env condition)
            ((Just (Bool true)) → (eval env consequent))
            ((Just (Bool false)) → (eval env alternative))
            (_ → (error "condition should be evaluated to a boolean value"))))
    ((Lambda _ _) → (Just (Closure expr env)))
    ((App fn arg) → (let [fnv (eval env fn)]
                      (match fnv
                        ((Just (Closure (Lambda x e) innerenv)) →
                            (do Maybe
                              (argv ← (eval env arg))
                              (eval ((x . argv) :: innerenv) e)))
                        (_ → (error "should apply arg to a function")))))
    ((Let x e1 in-e2) ⇒ (do Maybe
                          (v ← (eval env e1))
                          (eval ((x . v) :: env) in-e2)))
    ;; use fix point combinator to approach "Turing-complete"
    ((LetRec x e1 in-e2) → (eval env (Let "Y" (Lambda "h" (App (Lambda "f" (App (Var "f") (Var "f")))
                                                               (Lambda "f" (App (Var "h")
                                                                                (Lambda "n" (App (App (Var "f") (Var "f"))
                                                                                                 (Var "n")))))))
                                              (Let x (App (Var "Y") (Lambda x e1))
                                                     in-e2))))
    ((Binop op (e1 . e2)) => (let [v1 (eval env e1)
                                   v2 (eval env e2)]
                               (eval-op op v1 v2)))))

(begin
  (print "start")
  (let result (match (eval [] (LetRec "fact" (Lambda "n" (If (Binop Less ((Var "n") . (Num 2)))
                                                             (Num 1)
                                                             (Binop Mul ((Var "n") . (App (Var "fact")
                                                                                          (Binop Sub ((Var "n") . (Num 1))))))))
                                             (App (Var "fact") (Num 5))))
                ((Just (Num num)) ⇒ (print (int2str num)))
                (Nothing ⇒ (error "oops"))))
  (print result)
  (print "finish"))

License

Copyright © 2016 zjhmale

Distributed under the license BSD

Used by 1 package:
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