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Your First Program in 5 Minutes

In this quick walkthrough, you will write, verify, compile, and execute your first program in Aipo.

---

1. Hello, World!

Create a file named hello.aipo:

# hello.aipo
io.println("Hello from Aipo!")

Run it directly with the CLI:

aipo run hello.aipo

Expected output:

Hello from Aipo!

---

2. Structs, Invariants, and Methods

Let's model a bank account with an invariant guaranteeing a non-negative balance. Create account.aipo:

# account.aipo
struct Account {
    holder: String
    account_number: Int
    var balance: Float = 0.0
}

Account:init(holder: String, account_number: Int = 0, balance: Float = 0.0) {
    self.holder = holder
    self.account_number = account_number
    self.balance = balance
}

# Invariant: executed upon construction and every field mutation
Account:invariant {
    self.balance >= 0.0
}

Account:deposit(var self, amount: Float) {
    if amount <= 0.0 {
        return fail("Deposit amount must be positive")
    }
    self.balance += amount
}

Account:withdraw(var self, amount: Float) {
    if amount <= 0.0 {
        return fail("Withdrawal amount must be positive")
    }
    
    # Tries to execute the withdrawal. If self.balance >= 0.0 fails,
    # the attempt block rolls back the mutation automatically!
    attempt {
        self.balance -= amount
    } failed err {
        return fail("Withdrawal rejected: insufficient balance")
    }
}

# Instantiating the account using consistent colon (:) syntax
var acc = Account{ holder: "Alice Johnson", account_number: 1042, balance: 150.0 }

io.println(f"Account created for: {acc.holder}")
io.println(f"Initial balance: {acc.balance}")

acc.deposit(50.0)
io.println(f"Balance after deposit: {acc.balance}")

acc.withdraw(75.0)
io.println(f"Balance after withdrawal: {acc.balance}")

Run the program:

aipo run account.aipo

Expected output:

Account created for: Alice Johnson
Initial balance: 150.0
Balance after deposit: 200.0
Balance after withdrawal: 125.0

---

3. Inspecting Bytecode

Aipo provides full transparency into compiler output. You can disassemble the bytecode for any file:

aipo disasm account.aipo

The output shows bytecode mnemonics annotated with corresponding source line and column numbers.

---

4. Compiling to JavaScript

You can transpile the exact same program to JavaScript for Node.js or browser execution:

aipo build account.aipo -o dist/account.js
node dist/account.js

The emitted JavaScript provides bit-for-bit behavioral parity with the native Rust VM.