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Getting started with CX

Hello World

We will first create a Hello World CX application.

Create a hello-world.cx file with the following content.

package main

func main () {
    str.print("Hello, World!")
}

Running cx hello-world.cx prints out Hello, world!. More basic CX patterns and examples can be found in the examples directory.

Basic Options

cx --help will print available commands and options. cx --version prints the currently installed version of CX.

Frequently used options are:

  • --repl loads program and runs it in REPL mode useful for debugging
  • --web exposes endpoint for code evaluation at: http://127.0.0.1:5336/eval)

REPL tutorial

Once CX has been successfully installed, running cx should print this in your terminal:

CX 0.5.13
More information about CX is available at http://cx.skycoin.com/ and https://github.com/skycoin/cx/
:func main {...
	*

This is the CX REPL (read-eval-print loop), where you can debug and modify CX programs. The CX REPL starts with a barebones CX structure (a main package and a main function) that you can use to start building a program.

Let's create a small program to test the REPL. First, write str.print("Testing the REPL") after the *, and press enter. After pressing enter you'll see the message "Testing the REPL" on the screen. If you then write :dp (short for :dProgram or debug program), you should get the current program AST printed:

Program
0.- Package: main
	Functions
		0.- Function: main () ()
			0.- Expression: str.print("" str)
		1.- Function: *init () ()

As we can see, we have a main package, a main function, and we have a single expression: str.print("Testing the REPL").

Let's now create a new function. In order to do this, we first need to leave the main function. At this moment, any expression (or function call) that we add to our program is going to be added to main. To exit a function declaration, press Ctrl+D. The prompt (*) should have changed indentation, and the REPL now shouldn't print :func main {... above the prompt:

:func main {...
	*
*

Now, let's enter a function prototype (an empty function which only specifies the name, the inputs and the outputs):

* func sum (num1 i32, num2 i32) (num3 i32) {}
*

You can check that the function was indeed added by issuing a :dp command. If we want to add expressions to sum, we have to select it:

* :func sum

:func sum {...
	*

Notice that there's a semicolon before func sum. Now we can add an expression to it:

:func sum {...
	* num3 = num1 + num2

Now, exit sum and select main with the command :func main. Let's add a call to sum and print the value that it returns when giving the arguments 10 and 20:

:func main {...
	* i32.print(sum(10, 20))
30

Learning CX

To get your hand dirty with the CX language, you can read the following reference:

1. CX Book

You can find the book source code and its releases in its CX book Github repository.

2. Language Guide

You can find the language guide which is more up to date than the book in language guide section.