Re{solve} Hackathon Workshop: Cairo Programming Language

Summary of "Re{solve} Hackathon Workshop: Cairo Programming Language"

Overview: This workshop, led by David Barto (Developer Advocate at StarkWare) and Suton Chen, introduces the Cairo Programming Language, focusing on its general-purpose capabilities beyond just smart contracts on StarkNet. The session includes a detailed tutorial on setting up the development environment, basic programming concepts in Cairo, and testing methodologies.

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Key Technological Concepts and Product Features:

• Cairo Programming Language:
  • Used primarily for writing smart contracts on StarkNet but also supports general-purpose programming.
  • Syntax bears resemblance to Rust but differs fundamentally in compilation and proof generation.
  • Default numeric type is felt252 (field element with 252 bits), which is unique to Cairo and StarkNet's cryptographic foundations.
• Development Environment Setup:
  • StarkUp: The main tool to install Cairo dependencies, including:
    • scarb: A package manager for Cairo (handles dependencies, compilation).
    • StarkNet Foundry: A testing framework inspired by Ethereum’s Foundry but for Cairo.
    • devnet, sierra compiler, and others.
  • ASDF: A version manager installed alongside to handle multiple Cairo versions per project without Docker.
  • Installation instructions provided for Mac OS, Linux, and Windows (via WSL).
• Project Initialization and Management:
  • Use scarb init to create new Cairo projects.
  • scarb.toml file manages project configuration and dependencies, similar to Rust’s Cargo.
  • Extensions recommended for VS Code and Cursor editors for syntax highlighting and autocomplete:
    • toml and cairo 1.0.0 (by StarkWare).
• Basic Cairo Programming Concepts:
  • Functions: Defined with fn, requiring explicit return types.
  • Modules: Files are modules; linked via mod declarations in lib.cairo.
  • Unit Testing: Use #[cfg(test)] and #[test] attributes with scarb test to run tests.
  • Shadowing and Mutability:
    • Variables immutable by default.
    • Shadowing allowed by redefining variables with the same name.
    • Explicit mut keyword enables mutability.
    • Constants declared with const keyword and uppercase naming convention.
• Data Types and Arithmetic:
  • Unsigned integers: u8, u16, u32, u64, u128, usize.
  • Signed integers: i8, i32, i64, i128 (no i256 or isize).
  • Arithmetic operations supported with overflow and underflow protection that cause panics (tests use #[should_panic]).
  • Felt252 (Field Elements):
    • Default numeric type if no explicit type is given.
    • Supports addition, subtraction, multiplication.
    • No support for division or modulo (causes compilation errors).
    • No overflow or underflow protection due to modular arithmetic nature.
    • Used internally for cryptographic proofs.
    • Can encode "short strings" (up to 31 ASCII characters) by packing characters into a single felt.
  • Byte Arrays: For strings longer than 31 characters, supports unlimited length but only ASCII characters (no UTF-8 or accented characters).
• Advanced Math with Dependencies:
  • Cairo supports importing external libraries via scarb package manager.
  • Example: alexandria_math package for advanced math functions like fast exponentiation and square root.
  • Demonstrated adding dependencies in scarb.toml and using use statements to bring functions into scope.
• Gas Usage:
  • Gas metering is relevant only on StarkNet (not in vanilla Cairo).
  • Can be disabled for local testing (cairo_enable_gas = false).
  • Gas usage measures computational resources for smart contract execution on StarkNet.
• Learning Resources:
  • Official Cairo Book: https://www.cairo-lang.org/docs/
  • Recorded 3-hour deep-dive workshop on YouTube (link shared in chat).
  • Starklings: Interactive browser-based exercises for learning Cairo.
  • StarkNet Base Camp: A course that uses Starklings as graduation criteria.
• Upcoming Workshop:
  • Workshop #2 will focus on building smart contracts and testing with StarkNet Foundry.

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Summary of the Tutorial/Guide Elements:

• Step-by-step installation of Cairo environment using StarkUp.
• Creating and configuring a new Cairo project with scarb.
• Writing simple functions, defining modules, and running unit tests.
• Explaining mutability, shadowing, and constants.
• Handling integers and felts, including