#5 Foundation and Architecture: Why Design a New Programming Language? -> Example Code in Our Target Language.

To crystallize the goals and philosophy of our new C-style language, this section introduces example source code written in the proposed syntax and semantics of the language. This code is not only illustrative of its intended usage but also highlights the motivations behind its design, rooted in the practical capabilities of C++20/23 which powers its interpreter.

These examples are deliberately designed to reflect the essential traits of the language:

• Simplicity and clarity in syntax

• Safety and deterministic behavior

• Explicit memory and ownership management

• Compile-time evaluation and static typing

• Concurrency primitives built into the language

• Minimal standard runtime abstractions

The language borrows its surface syntax from the C/C++ family but enforces modern principles such as immutability by default, explicit mutability, explicit ownership transfer, and built-in safe types like Option, Result, and Slice.

1. Hello World — Minimal Entry Point

fn main() -> int {
    print("Hello, World!");
    return 0;
}

Key Observations:

• fn is the keyword for function definition

• main returns an integer, explicitly

• print() is a built-in function in the minimal standard library

• Semicolon enforces clear statement boundaries

• No global side-effects or preprocessor use

2. Immutable and Mutable Variables

fn demo() {
    let x: int = 10;       // Immutable by default
    let mut y: int = 20;   // Mutable with 'mut'

    y = y + x;
    print(y);              // Output: 30
}

Design Notes:

• let declares a variable; mut marks it mutable

• No implicit type promotion

• All variables are block-scoped

• Encourages value-oriented programming, discourages shared mutability

3. Ownership and Option Type

fn safe_divide(a: int, b: int) -> Option<int> {
    if b == 0 {
        return none;
    }
    return some(a / b);
}

fn use_divide() {
    let result = safe_divide(10, 2);
    if result is some(val) {
        print("Result: ", val);
    } else {
        print("Division by zero");
    }
}

Conceptual Design:

• Option<T> is a built-in tagged union: some(T) or none

• Pattern matching is minimal but expressive

• Avoids nulls entirely by requiring explicit handling

• Internally backed by std::optional in the C++ interpreter

4. Compile-Time Evaluation

const fn factorial(n: int) -> int {
    if n <= 1 {
        return 1;
    }
    return n * factorial(n - 1);
}

fn main() {
    const fact_5: int = factorial(5); // Computed at compile time
    print(fact_5);                    // Output: 120
}

Engine Behavior:

• const fn marks functions evaluable at compile-time

• Can be folded by the interpreter before execution

• Uses constexpr or consteval under the hood in C++20/23

• Supports embedded and systems programming via deterministic computation

5. Struct and Pattern Matching

struct Point {
    x: float;
    y: float;
}

fn distance(p: Point) -> float {
    return sqrt(p.x * p.x + p.y * p.y);
}

fn example() {
    let origin = Point { x: 3.0, y: 4.0 };
    print("Distance: ", distance(origin)); // Output: 5.0
}

Design Insight:

• Structs have named fields and no implicit constructors

• No inheritance; instead, structural or trait-based behavior

• Internally modeled using struct and std::variant where polymorphism is required

6. Generics and Traits (Concepts)

trait Addable {
    fn add(self, other: Self) -> Self;
}

fn sum<T: Addable>(a: T, b: T) -> T {
    return a.add(b);
}

Semantics:

• Traits define required behavior (similar to C++ concepts or Rust traits)

• Generics with constraint T: Addable

• Enforced at compile-time; no runtime overhead

• Backed by concepts and requires clauses in C++20

7. Concurrency with Spawn and Join

fn compute() -> int {
    let mut result: int = 0;
    for i in 0..100 {
        result = result + i;
    }
    return result;
}

fn parallel_sum() {
    let t1 = spawn compute();
    let t2 = spawn compute();

    let r1 = join t1;
    let r2 = join t2;

    print("Total: ", r1 + r2);
}

Runtime Behavior:

• spawn creates a concurrent task (internally backed by std::jthread)

• join blocks and retrieves the result

• No shared mutable state; each function returns its own value

• Thread-safe by design with no race condition primitives exposed by default

8. Error Handling via Result

fn open_file(path: string) -> Result<File, string> {
    if path == "" {
        return err("Empty path");
    }
    return ok(File {});
}

fn main() {
    let file = open_file("log.txt");
    if file is ok(f) {
        print("Opened successfully");
    } else if file is err(e) {
        print("Error: ", e);
    }
}

Design Philosophy:

• No exceptions

• All errors must be handled explicitly

• Result<T, E> is modeled using a discriminated union

• Backed internally by std::variant or equivalent C++ construct

9. Slices and Bounds Safety

fn print_slice(data: slice<int>) {
    for i in 0..data.len {
        print(data[i]);
    }
}

fn use_slice() {
    let arr = [1, 2, 3, 4];
    print_slice(arr[1..3]); // Prints: 2, 3
}

Safety Model:

• slice<T> is a view, not an owning container

• All indexing is bounds-checked by default

• Internally uses std::span<T> with range validation in debug builds

10. Modules and Imports

module math;

fn square(x: int) -> int {
    return x * x;
}
cppCopyEditimport math;

fn main() {
    print(math::square(5)); // Output: 25
}

Module Philosophy:

• File = module; explicit import/export

• No preprocessor; no text-based inclusion

• Namespaces resolved statically; no symbol collisions

• Mirrors C++20 modules and supports layered build architecture

Conclusion

The example code demonstrates a realistic and coherent C-style language that learns from the best practices of recent systems languages while avoiding their complexity and performance compromises. Each feature shown is backed by real capabilities in C++20/23, ensuring that both the interpreter and language design remain aligned with proven techniques in modern software engineering.

The examples also reflect our language’s goals:

• Simplicity with clarity

• Explicit memory and concurrency handling

• Compile-time power without hidden magic

• Strong, safe typing with low abstraction overhead