compact-coreledger-adts

name	compact-core:ledger-adts
description	Use when working with Compact on-chain state management using ledger ADTs including Cell, Counter, Map, Set, List, MerkleTree, or HistoricMerkleTree, or when needing to understand which operations are available in Compact vs TypeScript.

Ledger ADTs

Reference for Midnight's ledger abstract data types for on-chain state management.

Available ADTs

ADT	Purpose	Key Operations
Cell<T>	Single mutable value	read, write
Counter	Increment-only counter	increment, value
Map<K, V>	Key-value storage	lookup, insert, remove
Set<T>	Membership collection	member, insert, remove
List<T>	Ordered collection	append, nth, length
MerkleTree<T>	Membership proofs	insert, root, pathForLeaf
HistoricMerkleTree<T>	Historical roots	Same + resetHistory

Quick Examples

Counter

ledger counter: Counter;

export circuit increment(): Uint<64> {
    counter.increment(1);
    return counter.value();
}

Map

ledger balances: Map<Bytes<32>, Uint<64>>;

export circuit get_balance(user: Bytes<32>): Uint<64> {
    const result = balances.lookup(user);
    return if result is Maybe::Some(balance) { balance } else { 0 };
}

MerkleTree

ledger members: MerkleTree<Bytes<32>>;

export circuit prove_membership(
    leaf: Bytes<32>,
    path: Vector<Bytes<32>, 20>
): Boolean {
    const computed_root = merkleTreePathRoot(leaf, path);
    return computed_root == members.root();
}

Compact vs TypeScript Operations

Some ADT operations are only available in TypeScript:

ADT	Compact	TypeScript Only
Counter	value, increment	-
Map	lookup, insert, remove	entries, keys
Set	member, insert, remove	entries, size
List	nth, append	entries, length
MerkleTree	insert, root	pathForLeaf, iteration

References

• Counter - Counter operations and patterns
• Collections - Map, Set, List operations
• Merkle Trees - MerkleTree and HistoricMerkleTree
• Kernel - Special kernel operations