Ivy Syntax

Ivy gives you essentially all the flexibility of Bitcoin Script, but gives you some additional affordances and conveniences:

• named variables
• named "clauses"
• static (and domain-specific) types
• familiar syntax for functions and operators

This is an example of an Ivy contract template:

contract LockWithPublicKey(publicKey: PublicKey, val: Value) {
  clause spend(sig: Signature) {
    verify checkSig(publicKey, sig)
    unlock val
  }
}

Each contract template needs to be passed some contract arguments to turn it into a contract. Each argument has a type, such as PublicKey, Value, or Signature.

This contract can be parameterized with a cryptographic public key, publicKey, to create an address.

You must also pass some Value—the Bitcoins to be protected. Every contract template has such a parameter, in this case named val. To instantiate this contract on the Bitcoin mainnet, you would need to provide some amount of BTC—actual value, not just data.

Each contract has one or more clauses. To unlock the contract, you need to invoke one of its clauses, pass it one or more clause arguments—in this case, a signature—and satisfy each of its conditions.

In this case, the spend clause only enforces one condition. It uses the checkSig function to enforce that sig must be a valid signature on the transaction by the private key corresponding to the prespecified publicKey.

Finally, each clause needs to unlock the locked value, with a statement like unlock val.