CatLang

A language based on S-expressions. Written on Python, uses SLY library to parse and tokenize code.

To run code install sly:

pip3 install sly

Usage:

python3 catlang.py <file> [-d]

Features

Implemented:

• Variables
• Output keyword
• Basic math operations
• Basic comparison operators
• If statement
• While statement
• Functions
• Comments

Examples

Comments and prints

To comment a line use percent symbol %, to print text in console use out keyword

% Output text to console
(out "Hello, world!" . "from CatLang")  % Dot means newline

Variables

Variables can be created via assign symbol =

(= int 10)
(= float 99.47)
(= str "Hello, world")
(= bool T)  % T means True and F means False

% Let's output this variables
(out 
  "int = " int .
  "float = " float .
  "str = " str .
  "bool = " bool
)

Operators

CatLang supports next math operations:

• + to add
• - to sub
• * to mul
• / to div
• ^ to pow

And some logical operations

• & to and
• | to or
• ! to not

Eq operations:

• = to assign
• += to add and assign
• -= to sub and assign
• *= to mul and assign
• /= to div and assign

And some comparsion operators:

• > to gt
• >= to gte
• < to lt
• <= to lte
• != to ne
• == to iseq

All operators must be written in prefix form

(out (+ 1 1))
(out (- 0 4))  % Way to create negative numbers
(out (* 4.5 2))
(out (/ 42 144))
(out (^ 2 4))

(out (! F))  % Negation of False is True

(out (> 1 0))
(out (<= 1.5 3))
(out (!= 1 7))
(out (== 3.0 3))

Statements

CatLang supports only if and while statements, conditional statements can be executed through if keyword

(if (!= 3 4) (
  (out "Well, 3 it's not equal 4")
))

(if (!= (+ 0.1 0.2) 0.3) (
  (out 
    "Wait... what? " .
    "(" (+ 0.1 0.2) ")"
  )
))

Cycles may be executed via while keyword

(= i 5)
(while (>= i 0) (
  (out i "...")
  (-= i 1)
))

Functions

Functions can be executed with or without one parameter. To define function use def keyword

(def say_hi () (
  (out "hi")
))

(say_hi)  % Execute

(def fact (n) (
  (= f 1)
  (while (> n 1) (
    (*= f n)
    (-= n 1)
  ))

  (ret f)  % Return f
))

% 5! = 1 * 2 * 3 * 4 * 5
(out "5! = " (fact 5))