Hello, Ora

Ora is a smart contract language for the EVM. It compiles through MLIR to bytecode, with explicit memory regions, error unions, refinement types, and built-in formal verification. The compiler is written in Zig.

This book teaches Ora from first contract to production-grade vault. Each chapter adds features to a running example.

Note: This book was written with AI assistance and reviewed by the Ora team. If you find inaccuracies, please open an issue or PR — the compiler is the source of truth, not this text.

Install

git clone https://github.com/oralang/Ora.git
cd Ora
./setup.sh
zig build

Verify the install:

./zig-out/bin/ora --help

Your first contract

Create a file called counter.ora:

contract Counter {
    storage var count: u256 = 0;

    pub fn increment() {
        count += 1;
    }

    pub fn get() -> u256 {
        return count;
    }
}

Build it:

./zig-out/bin/ora build counter.ora

Format it:

./zig-out/bin/ora fmt counter.ora

What just happened

• contract Counter declares a contract — the top-level unit in Ora.
• storage var count: u256 = 0 declares a persistent storage variable. The storage keyword is explicit — Ora never hides where data lives.
• pub fn increment() is a public function, callable from outside the contract. Functions without pub are internal.
• count += 1 modifies storage. The compiler tracks this as a write effect.
• fn get() -> u256 returns a value. The -> arrow separates parameters from return type.

Ora vs Solidity at a glance

Concept	Solidity	Ora
Contract	contract C { }	contract C { }
Storage variable	uint256 count;	storage var count: u256;
Function visibility	function f() public	pub fn f()
Return type	returns (uint256)	-> u256
Variable declaration	uint256 x = 5;	let x: u256 = 5;
Error handling	require(...) / revert	Error unions (!T | Error)
Memory annotation	memory keyword on params	Region system (storage, memory, calldata, transient)

The syntax differences are deliberate. Ora favors explicitness: types are always annotated, regions are always visible, and errors are always in the type system.

Project scaffolding

For larger projects, use ora init:

./zig-out/bin/ora init my-project
cd my-project

This creates an ora.toml config, a contracts/main.ora starter file, and a README.md.

CLI quick reference

Command	Purpose
ora build file.ora	Compile to bytecode
ora fmt file.ora	Format a single file
ora fmt src/	Format all .ora files in a directory (recursive)
ora fmt --check file.ora	Check formatting (CI)
ora emit --emit-mlir file.ora	Emit Ora MLIR
ora emit --emit-ast file.ora	Emit parsed AST
ora emit --emit-bytecode file.ora	Emit EVM bytecode
ora init name	Scaffold a new project

Further reading

• Getting Started — full installation details
• Code Formatter — formatter options and configuration