quick_tour.md

Quick tour

Installation

Install the CO2:

curl --proto '=https' --tlsv1.2 -sSf https://hkalbasi.github.io/co2/install.sh | sh

It installs co2cc, co2rustc and co2cargo in your PATH. See installation page for other installation methods. You can also start without installing it by using it online in godbolt's compiler explorer.

CO2 as a C compiler

The co2cc is a drop in replacement for a C compiler like gcc. You can compile almost every (See incompatibilities) C code like:

co2cc foo.c

It tries to remain compatible with gcc in flags and CLI interface, so you can use it as a C compiler in the build systems like cmake.

Beyond C compiler

But CO2 is not a simple C compiler, and even co2cc is capable of compiling CO2 specific features. Here is a tour over CO2 features:

// Use statements can import from Rust std.
// They should be at the beginning of the file due parser technical limitations. 
use std::vec::Vec;
use std::option::Option;

// You can use rust primitives like i32 in C declarations.
int c_style_function(int a, i32 b) {
    return a + b;
}

// You can also define function signature using Rust syntax, to define a function with Rust ABI.
fn rust_style_function(a: i32, b: i32) -> i32 {
    // The body is still C.
    goto label;
    label:
        return c_style_function2(a, b); // Forward declarations are optional. 
}

#include <stdio.h>

i32 c_style_function2(int a, int b) {
    printf("c_style_function2(%d, %d)", a, b);
    return c_style_function(a, b);
}

int main() {
    Vec::<i32> v = Vec::<i32>::new(); // You can use generic Rust types and functions.
    for (int i = 0; i < 5; i++) {
        v.push(2 * i); // You can call Rust methods.
    }

    return 0;
}

Integration with Rust

While with co2cc you can use the Rust standard library, for adding Rust dependencies, and using the co2 code as a Rust crate, you need co2cargo.

Using co2cargo init, you can create a co2 binary crate. You can run it with co2cargo run, add dependencies using co2cargo add dep, and almost all cargo commands which are supported. Cargo commands which are dependent on a separate tool (like cargo fmt, cargo clippy, ...) are not supported (see exact list here).

Next steps

• Learn more about the language