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Control Flow Statements

Pebble supports a variety of control-flow mechanisms, inspired by both functional and imperative styles.
They allow expressing branching logic, looping, and pattern matching directly in contracts.

If / Else​

Standard conditional branching:

if (amount > minReceiveAmount) {
    trace("Valid amount");
} else {
    fail "Amount too low";
}

Internally, this compiles to conditional UPLC expressions.

Match / Case​

Pattern matching is a core feature in Pebble, especially for Cardano-specific types like Credential, Option, or Datum.

assert case ownerPaymentCreds
    is PubKeyHash{ hash } => tx.signatories.includes(hash)
    is Validator{ hash }  => tx.inputs.some(({ resolved }) =>
        resolved.credential.hash() === hash
    );

For Loops​

Pebble allows imperative for loops. They are compiled into functional recursion under the hood.

for (let i = 0; i < tx.inputs.length(); i = i + 1) {
    trace(tx.inputs[i]);
}

While Loops​

Pebble also supports while loops are also supported

let i = 0;
while (i < tx.outputs.length()) {
    trace(tx.outputs[i]);
    i = i + 1;
}
tip

On-chain, both for and while are bounded by transaction data size.

They cannot introduce unbounded computation, as UPLC enforces resource limits.