Getting Started

cowlang is a programming language that is inspired by Typescript and Dart.
Getting best of both languages in one place.

Quick Links

• Requirements
• Installation
• Development Setup
• Running Code
• REPL
• Syntax
  • Variables
    • Variable Types
  • Strings and Interpolation
  • Comments
  • Printing
  • Conditionals
  • Loops
  • Arrays
  • Functions
    • Paramter Types
  • Operators
  • Keywords
  • Built-in Types
• In Progress
• Comming Soon Features
• Changelog

Requirements

• Node.js
• Typescript
• Cowlang Language Support (VS Code Extension)

Installation

The interpreter can be installed using following command

npm install -g @cowlang/engine

Above command may not work if package is not available on npm. In that case, for time being, follow the steps Dev Setup to try it out

Dev Setup

1. Clone the project and cd in the project root
2. Building

   tsc

3. Installing interpretor globally

   npm install . -g

4. Now you can run cowlang code files that end with .cow extenstion

Running Code

Code files in cowlang have .cow extension. In order to run your cow file, run:

cowlang milk-production.cow

Above command will run file named milk-production.cow

REPL

Cowlang has built-in support to run code directly in the terminal. Just like Node REPL there's a cowlang REPL.
To enter in REPL, run:

cowlang

Running above command print something like below:

cowlang REPL vx.y.x
>

Now you can write your code directly inside terminal, and it gets executed everytime you press enter.

Syntax

Variables

cowlang supports two kinds of variables, one which can be reassigned and other which are constant and cannot be reassigned.

• Variables, that can be reassigned

  var someVar = 10
  someVar = 20

  Variables, can also be declared but initialized later, an uninitialized variable must've have expilicit dynamic type

  var name: dynamic; # Note the semicolon, it is mandatory here
  name = "John Doe"

• Constants, that cannot be reassigned

  const numDaysInWeek = 7
  numDaysInWeek = 8

Variable Types

Type can be declared after a colon following the identifier.

var name: string = "John Doe"
var age: number = 20

Types are infered in cowlang, if no type is given interpreter gets it from the value assigned

var name = "John Doe"
name = 20 # it will throw error, because name is string

To create dynamic variable, that can have any value of any type use dynamic type

var store: dynamic = "some value"
store = 20
store = false
store = [1.2, 3.5]

Strings and Interpolation

Strings are declared using double quotes

var name = "John Doe"

To evaluate a variable inside the string prefix variable with $

const message = "My name is $name"

To insert expressions in strings ${} syntax is used

const result = "2 + 2 = ${2 + 2}"

Comments

Anything that starts with # is considered as comment and ignored

# This is a comment
print("Hello") # Prints Hello

Printing to console

print is built-in function that is used to log the output

print("Hello World!")

print(5 + 9)

const PI = 1.1314

print("PI is $PI")

Conditionals

var age = 20

if (age < 18) {
  print("Immature")
} else if (age == 18) {
  print("You can get your ID")
} else {
  print("Retire")
}

Loops

var start = 1

const end = 10
const tableof = 8

while (start <= end) {
  print("$tableof * $start = ${tableof * start}")
  start = start + 1
}

Arrays

var subjects = ["Physics", "Maths", "Computer", "Literature"]

length is built-in function to get the length of an array

print("Number of subjects are ${length(subjects)}")

Functions

Functions are declared using fn keyword

fn add(a,b){
    a + b
}

Note: Functions in cowlang automatically return last evaluated result

Functions can return functions, that are executed by appending another pair of parens

fn padder(padding){
    fn add(a,b){
        padding + a + b
    }
}

const result = padder(10)(5,20)
print(result)

Parameter Types

Parameter types can be given same as in variables

fn add(a: number, b: number){
 a + b
}

add(1,2) # prints 3
add(1, true) # throws error, becuase 'true' is not a number

Operators

Operator	Description
>	Greater Than
>=	Greater Than Or Equals
<	Less Than
<=	Less Than Or Equals
==	Equals
!=	Not Equals
=	Assignment
&&	And
||	Or
and	And
or	Or

Keywords

Keyword	Description
var	Declares a variable
const	Declares a constant
while	Loop
if	Conditional
else	Conditional
fn	Declares a function
and	Logical 'and'
or	Logical 'or'

Built-in Types

Type	Description
dynamic	A dynamic variable can have any type
string	String type
number	Integer and floats
array	Array
object	Object

In Progress

• Param and return types

Plans

Features that we're going to add in future

• Enums
• Interfaces
• Classes
• Tuples

Architecture level things we're considering

• Compiling to Byte Code
• Adding Multi-threading

Changelog