Margarine Language Tutorial

Welcome to the Margarine language tutorial! This guide will take you from the basics to advanced features, with runnable examples. To run any example, save it to a file (e.g., hello.mar) and run:

cargo r run hello.mar

1. Hello World

fn main() {
    print("Hello, world!");
}

2. Variables and Types

var x = 42;
var y: float = 3.14;
var name = "Margarine";

3. Functions

fn add(a: int, b: int) -> int {
    return a + b;
}

fn main() {
    print(add(2, 3));
}

4. Control Flow

If/Else

fn main() {
    var x = 10;
    if x > 5 {
        print("x is large");
    } else {
        print("x is small");
    }
}

Match

fn main() {
    var x = 2;
    match x {
        1 => print("one"),
        2 => print("two"),
        _ => print("other"),
    }
}

5. Loops

fn main() {
    for i in 0..5 {
        print(i);
    }
    var x = 0;
    while x < 3 {
        print(x);
        x += 1;
    }
    loop {
        break;
    }
}

6. Structs and Enums

Structs

struct Point { x: int, y: int }

fn main() {
    var p = Point { x: 1, y: 2 };
    print(p.x);
}

Enums

enum Option<T> { Some: T, None }

fn main() {
    var x = Option::Some(42);
    match x {
        Option::Some(val) => print(val),
        Option::None => print("none"),
    }
}

7. Traits and Impls

trait Display { fn show(self) -> str; }

struct User { name: str }

impl Display for User {
    fn show(self) -> str {
        return self.name;
    }
}

fn main() {
    var u = User { name: "Alice" };
    print(u.show());
}

8. Generics

fn identity<T>(x: T) -> T { return x; }

fn main() {
    print(identity(123));
    print(identity("abc"));
}

9. Modules and Imports

mod math;

fn main() {
    print(math::add(1, 2));
}

10. Extern and FFI

extern "https://example.com/repo" as ext;
use ext::lib;

fn main() {
    print(lib::external_function());
}

11. Pattern Matching and Destructuring

fn main() {
    var (a, b) = (1, 2);
    print(a);
    print(b);
}

12. Attributes

@test
fn some_test() {
    assert(3 == 3, "what?")
}

13. Error Handling

Compile-time errors are reported with source locations. For runtime errors, use Option, Result, and pattern matching.

14. Advanced: Closures, Lists, and More

fn main() {
    var add = |a, b| a + b;
    print(add(2, 3));
    var xs = [1, 2, 3];
    print(xs[0]);
}

15. Full Example

struct Counter { value: int }

impl Counter {
    fn inc(self) -> Counter {
        return Counter { value: self.value + 1 };
    }
}

fn main() {
    var c = Counter { value: 0 };
    c = c.inc();
    print(c.value);
}

For more, see the reference and examples.

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