output_append.md

Output Append Example

CellScript models updates as proposed output Cells. It does not update a CKB cell in place.

Conceptual source shape:

resource Log has store, create, consume, replace {
    owner: Address,
    bytes: Vec<u8>,
}

action append(log: Log, suffix: Vec<u8>) -> next_log: Log
where
    let next = log.bytes
    next.extend_from_slice(suffix)
    create next_log = Log {
        owner: log.owner,
        bytes: next
    }

Expected transaction shape:

• one input consumes the old Log
• one output creates the updated Log
• preserved fields such as owner must be constrained explicitly
• changed fields such as bytes must satisfy the compiled transition checks

Relevant inspection commands:

cellc check contract.cell --target-profile ckb
cellc constraints contract.cell --target-profile ckb --json

For CKB, the builder must also provide occupied-capacity and transaction-size evidence for the proposed output.