The Charly programming language

This is my try at writing an interpreter of a dynamic language from scratch with my bare hands. It is implemented in Crystal at has no dependencies.

Syntax

Semicolons are completely optional!

Declaring a variable

let number = 900
let float = 5.5928
let string = "Hello World"
let boolean = true
let array = [1, "charly", false]
let nullvalue = null
let object = {
  let name = "leonard"
  let age = 16
}

Declaring a function

func callback(value, callback) {
  callback(value)
}

let result = callback(25, func(value) {
  value * 2
})

result # => 50

Repeat & While loops

5.times(func(i) {
  print("Hello")
})

let i = 0
while (i < 10) {
  print("In a while loop")
  i = i + 1
}

User Input

# Strings
let input = gets()
print(input)

# Numbers
let input_number = gets().to_n()
print(input_number)

Primitive types

25.type()                           # => Numeric
25.5.type()                         # => Numeric
"Charly".type()                     # => String
[1, 2, 3].type()                    # => Array
null.type()                         # => Null
false.type()                        # => Boolean
(class Box {}).type()               # => Class
(func() {}).type()                  # => Function
{ let name = "charly" }.type()     # => Object

Including other files

# Include a file in the current directory
require("external.charly")

# Include the someotherlibrary from the standard library
require("someotherlibrary")

Working with arrays

let array = [1, 2, 3]
array.push(4)
print(array) # => [1, 2, 3, 4]

Classes & Objects

class Person {
  let name
  let age

  func constructor(name, age) {
    self.name = name
    self.age = age
  }
}

let leonard = Person("Leonard", 16)
print(leonard.name) # "Leonard"
print(leonard.age) # 16

Everything is an object... kind of

When you write 5, the interpreter actually treats it as a primitive. There are no funny castings or object instantiations. You can normally write code like 2 + 5 and it will work. Once you do something like 5.times(func(){}), the interpreter searches the current scope for an object called Numeric and checks if there is a function called times on it. If it finds the method, it injects a variable called self into the function's stack and executes it.

This allows the interpreter to reuse the same object for all primitives.

This principle applies to all language primitives. The Array object for example, specifies a method called push which inserts an element into the array.

Installation

I have only tested this on macOS 10.12. It should theoretically work on linux systems too.

You will need a working crystal installation.

To install the charly command and automatically copy it to the /usr/bin folder, run install.sh. You will be prompted for your admin password (used to copy to /usr/bin).

CLI options

$ charly -h
Usage: charly [options] filename [arguments]
    -f FLAG, --flag FLAG             Set a flag
    -h, --help                       Show this help
    -v, --version                    Show the version number

Flags:
    ast                              Display AST's of parsed programs
    tokens                           Display tokens of parsed programs
    noexec                           Disable execution
    noprelude                        Don't load the prelude file
    stackdump                        Dump the top-level stack at the end of execution

Contributors

• KCreate - Leonard Schütz

Inspired by

• Javascript
• C
• Ruby

License

The MIT License (MIT)

Copyright (c) 2016 Leonard Schuetz

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.