Hello World

Traditionally, the very first program you write when learning a new programming language is one that prints “Hello, World!” to the screen. In Inference, however, we do not have built-in string and printing functionality. Instead, we will write a simple program that returns a magic number from a function. Later, by executing this program, we will see the result in the terminal.

Writing the Program

First, we need to create a new file for our program. Inference uses the .inf file extension for its source code files. Create a new file named hello_world.inf and open it in your favorite text editor. Then, add the following code to the file:

fn hello_world() -> i32 {
    return 42;
}

This code defines a function named hello_world that takes no parameters and returns a 32-bit signed integer (i32). The function simply returns the number 42.

Understanding the Code

Let’s break down the code to understand its components:

fn is a keyword used to define a function in Inference;
hello_world is the name of the function;
() is a pair of parentheses that groups the function parameters. In this case, there are no parameters;
-> reads as “right arrow” and indicates the return type of the function;
i32 specifies that the function returns a 32-bit signed integer;
return is a keyword used to return a value from a function;
42 is the integer value (or literal) being returned by the function.

In the appendix, Language Reference, you can find more information about Inference keywords and data types.

We see that the hello_world function is defined without any container or module. If Inference sees such a function in a file, a standard module is created automatically and the function is placed inside it. To be able to call this function from outside the module, the export attribute is added automatically to the function.

Compiling the Program

To compile an .inf file into an executable binary, we use the Inference compiler, which is invoked via the command line using the infc command. Open your terminal, navigate to the directory where you saved hello_world.inf, and run the following command:

On Linux or macOS:

$ infc --codegen -o hello_world.inf

On Windows:

> infc --codegen -o hello_world.inf

As a result, the compiler will generate a Wasm binary module named hello_world.wasm in the out directory.

The --codegen flag tells the compiler to generate code, and link modules. The -o flag tells the compiler to output directory.

Running the Program

To execute the compiled Wasm binary, we can use any preferred Wasm runtime. In this example and in this book, we will use wasmtime, a popular and easy-to-use Wasm runtime. You can install and learn more about wasmtime from its official website.

Once you have wasmtime installed, you can run the hello_world.wasm binary using the following command: