What is Ralph

Ralph is the smart contract programming language built specifically for Alephium. It is statically typed, compiled, and designed around the UTXO model, which makes it fundamentally different from Solidity and most EVM-compatible languages.

How Ralph differs from Solidity

	Ralph	Solidity
Execution model	UTXO-based	Account-based
Asset handling	Built into the language	Via ERC standards
Reentrancy attacks	Not possible by design	Require guards
Gas model	Predictable, fixed per opcode	Variable
State storage	Explicit mutable/immutable fields	Single storage mapping

Contracts and scripts

Ralph has two top-level constructs: Contracts hold state and can be called repeatedly. They live at a fixed address on-chain and persist between transactions. TxScripts are one-shot transaction scripts. They execute once as part of a transaction and have no persistent address. Use them to interact with contracts, transfer assets, call functions, deploy new contracts.

Mutable and immutable fields

Every contract declares its fields upfront. Fields are either mut (can change after deployment) or immutable (set once at deployment, cheaper to read):

Contract TokenFaucet(
  symbol: ByteVec,        // immutable
  name: ByteVec,          // immutable
  decimals: U256,         // immutable
  mut balance: U256       // mutable
) {
  pub fn getSymbol() -> ByteVec {
    return symbol
  }

  @using(updateFields = true)
  pub fn withdraw(amount: U256) -> () {
    balance = balance - amount
  }
}

Attempting to modify an immutable field is a compile error.

Asset permissions

Ralph uses annotations to declare when a function touches assets. This prevents accidental asset loss and makes auditing straightforward:

Annotation	Meaning
`@using(assetsInContract = true)`	Function can use assets held by the contract
`@using(preapprovedAssets = true)`	Caller must approve assets before calling
`@using(updateFields = true)`	Function modifies mutable contract fields
`@using(checkExternalCaller = false)`	Disables the default caller check

Events

Contracts emit events to log activity. Events are indexed by the explorer and queryable via the API:

Contract TokenFaucet(...) {
  event Withdraw(to: Address, amount: U256)

  pub fn withdraw(to: Address, amount: U256) -> () {
    emit Withdraw(to, amount)
  }
}

Smart Contracts

How Ralph differs from Solidity

Contracts and scripts

Mutable and immutable fields

Asset permissions

Events

Next steps

Deploying contracts

Interacting with contracts

​How Ralph differs from Solidity

​Contracts and scripts

​Mutable and immutable fields

​Asset permissions

​Events

​Next steps

Deploying contracts

Interacting with contracts

How Ralph differs from Solidity

Contracts and scripts

Mutable and immutable fields

Asset permissions

Events

Next steps