dzhulk/jopa-scheme

Just learning rust

Simple scheme like lang interpreter

How to run:

cargo run -p jopc -- examples/main.scm

You can also run a REPL:

cargo run -p repl

wasm version:

cd www/
./server.sh
open http://localhost:8000/index.html

Built-ins:

+ - / *
> < >= <= =
nil?
list?
length
or and not
if - (if (cond) () ())
do - execute blocks of code, returns last value
cons - (cons el list) - push to front
conj - (cons el list) - append to list
car  - (car list) - get list head
cdr  - (cdr list) - get list tail
concat - (concat "string" 1 (list 1 2 3)) - join elements to string
println
define - define function or variable
list   - construct new list (list 1 2 3)

Some examples

map:

(define (map fn lst)
  (do
    (define (mapaux fn lst acc)
      (if (nil? lst) acc
        (mapaux fn (cdr lst) (conj (fn (car lst)) acc))))
      (mapaux fn lst nil)))


(map (lambda (x) (* x x)) (list 2 3 4 5 6))

FizzBuzz:

(define (fizzbuzzaux n curr acc)
    (if (< curr n)
        (fizzbuzzaux n (+ curr 1)
            (if (= (% curr 15) 0)
                (conj "FizzBuzz" acc)
                (if (= (% curr 3) 0)
                    (conj "Fizz" acc)
                    (if (= (% curr 5) 0)
                        (conj "Buzz" acc)
                        (conj curr acc)))))
        acc))

(define (fizzbuzz n)
    (fizzbuzzaux (+ n 1) 1 nil))

(println (fizzbuzz 100))

Fibonacci:

(define (fib n)
    (if (<= n 2)
        1
        (+ (fib (- n 1))
           (fib (- n 2)))))

(fib 20)

;; faster version

(define (fastfib n)
  (do
    (define (fibaux n acc)
      (if (= (length acc) n)
        acc
        (fibaux
          n
          (cons (+
                  (car acc)
                  (car (cdr acc)))
                acc))))
      (reverse (fibaux n (list 1 0)))))

(fastfib 50)

Filter & reduce:

(define (filter pred coll)
  (do
    (define (filteraux pred coll acc)
      (if (nil? coll)
        acc
        (if (pred (car coll))
          (filteraux pred (cdr coll) (conj (car coll) acc))
          (filteraux pred (cdr coll) acc))))
    (filteraux pred coll nil)))

(define nums (list 1 2 3 4 5 6 7 8 9 10))

;; select even elements
(define even
  (filter
    (lambda (el) (= (% el 2) 0))
    nums))

(println even)

(define (reduce fn coll init)
  (if (nil? coll)
    init
    (reduce fn (cdr coll) (fn (car coll) init))))

;; calculate list product
(reduce (lambda (el acc) (* el acc)) nums 1)

;; hof test
(define (even? el) (= (% el 2) 0))

(filter even? nums)

(define odd? (lambda (el) (not (= (% el 2) 0))))

(filter odd? nums)