compact-coreledger-adts

name	compact-coreledger-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.
metadata	{"author":"aaronbassett"}

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

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