arepa-lang

arepa is a tiny interepreted programming language based on LISP.

To run a program:

# Install ts-node globally and run
ts-node src/index.ts src/test.arp

Arithmetic

(+ 10 3) # Output = 13
(* 2 (+ 4 1)) # Output = 10
(/ 100 (/ 25 (+ 2 3))) # Output = 20

Conditionals

Comparisons can be done using the if operator

# Syntax: (if <condition> <true expression> <false express>)
# If "condition" is evaluated to true, then execute "true expression"
# and return its value. If it is evaluated to false,
# then execute "false expression" and return its value.

(if 1 2 3) # Output = 2
(if (- 1 1) 2 3) # Output = 3
(if 0 1 (if 1 4 5)) # Output = 4
(if 1 "hello" "goodbye") # Output = "hello"

Lists

Everything in arepa inside a pair of () is a list. A list can be a set of any other type.

(1 2 3 4)
("a" "b" "c")
(1 (1 2) 4)

Functions

Functions are a powerful construct in any language. They can be defined in arepa using the defunc operator.

(
    (defunc add (a b) (+ a b)) (add 1 2)
)
# Output = 3

As arepa is an interpreted language, the function definition should be before the function call. You can declare multiple functions and construct nested patterns.

(
    (defunc add (a b) (+ a b))
    (defunc square (a) (* a a))
    (square 2) # Output = 4
    (add 2 (square 4)) # Output = 18
    (defunc concat_w_space (a b) (+ a " " b))
    (concat_w_space "Have" "an" "arepa!") # Output = Have an arepa!
)

Recursion is not supported yet (I'll be working on it next!).

Remainder calculation can be done by using an inbuilt operator re. This can be used to build functions with conditional bodies.

(
    (defunc even_or_odd (num) (if (re num 2) "odd" "even"))
    (even_or_odd 4) # Output = "even"
    (even_or_odd 7) # Output = "odd"
)