Collection types

Rell supports the following collection types:

list<T> - An ordered list that allows duplicate elements.
set<T> - An unordered set that does not contain duplicate elements.
map<K,V> - A key-value map.

Properties of collection types

Mutable: You can dynamically add or remove elements.
Map key or set element: Only non-mutable types can be used as map keys or set elements.

Mutable collection types

Collection types (list, set, map): Always mutable.
Nullable type: Only if the underlying type is mutable.
Struct type: If the struct has a mutable field or a field of a mutable type.
Tuple: If an element type is mutable.

Creating collections

function foo() {
  // list
  val l1 = [1, 2, 3, 4, 5, 1];
  val l2 = list < integer > ();

  // set
  val s = set < integer > ();

  // map
  val m1 = ['Bob': 123, 'Alice': 456];
  val m2 = map < text, integer > ();
}

`list<T>`

A list is an ordered collection type that allows duplicate elements.

Constructors

list<T>() - Creates a new empty list.
list<T>(list<T>) - Creates a copy of the given list (a list of a subtype is also acceptable).
list<T>(set<T>) - Creates a copy of the given set (a set of a subtype is also acceptable).

Functions

Function	Description
`.add(T): boolean`	Adds an element to the end of the list. Always returns `true`.
`.add(pos: integer, T): boolean`	Inserts an element at a given position in the list. Always returns `true`.
`.add_all(list<T>): boolean`	Adds all elements from the given list to the end of the list.
`.add_all(set<T>): boolean`	Adds all elements from the given set to the end of the list.
`.add_all(pos: integer, list<T>): boolean`	Inserts all elements from the given list at the specified position in the list.
`.add_all(pos: integer, set<T>): boolean`	Inserts all elements from the given set at the specified position in the list.
`.clear()`	Removes all elements from the list.
`.contains(T): boolean`	Checks if the list contains the specified element.
`.contains_all(list<T>): boolean`	Checks if the list contains all elements from the given list.
`.contains_all(set<T>): boolean`	Checks if the list contains all elements from the given set.
`.empty(): boolean`	Returns true if the list is empty, otherwise returns false.
`.index_of(T): integer`	Returns the position of the first occurrence of the element in the list. Returns `-1` if the element isn't found.
`.remove(T): boolean`	Removes the first occurrence of the specified element from the list. Returns `true` if found.
`.remove_all(list<T>): boolean`	Removes all elements from the list that are present in the given list.
`.remove_all(set<T>): boolean`	Removes all elements from the list that are present in the given set.
`.remove_at(pos: integer): T`	Removes the element at the given position in the list and returns it.
`.repeat(n: integer): list<T>`	Returns a new list, which is the old list repeated "n" times. Always creates a new list (even if n = 1).
`.size(): integer`	Returns the number of elements in the list.
`.reverse()`	Reverses the order of elements in the list in place. Returns nothing.
`.reversed(): list<T>`	Returns a reversed copy of the list. Always creates a new list (even if the old list is empty or has one element).
`._sort()`	Sorts the list in ascending order. Returns nothing.
`.sorted(): list<T>`	Returns a sorted copy of the list in ascending order.
`.to_text(): text`	Returns a text representation of the list, e.g., `'[1, 2, 3, 4, 5]'`.
`.sub(start: integer[, end: integer]): list<T>`	Returns a sub-list (start-inclusive, end-exclusive) from the list.

Special operators

[] - Accesses or modifies an element at a specified index in the list.
in - Checks if a specified value exists in the list, returning true if it does.

Example:

function example_list() {
    // Creating a list of transactions
    val transactions = list<Transaction>();

    // Adding transactions to the list
    transactions.add(Transaction(id = 1, amount = 100, sender = "Alice", recipient = "Bob"));
    transactions.add(Transaction(id = 2, amount = 200, sender = "Bob", recipient = "Charlie"));
    transactions.add(Transaction(id = 3, amount = 150, sender = "Charlie", recipient = "Alice"));

    // Accessing a transaction by index
    val firstTransaction = transactions[0];
    print("First transaction amount: ${firstTransaction.amount}");

    // Modifying a transaction at a specific index
    transactions[1] = Transaction(id = 2, amount = 250, sender = "Bob", recipient = "Charlie");

    // Using contains with a custom equality check
    val searchTransaction = Transaction(id = 3, amount = 150, sender = "Charlie", recipient = "Alice");
    if (searchTransaction in transactions) {
        print("Transaction found in the list");
    }

    // Using sub to get a portion of the list
    val subList = transactions.sub(0, 2);
    print("Sub-list size: ${subList.size()}");

    // Creating a reversed copy of the list
    val reversedList = transactions.reversed();

    // Converting the list to text
    print("Transactions: ${transactions.to_text()}");
}

`set<T>`

An unordered collection type that does not allow duplicate elements.

struct Address {
    value: text;
}

function example_set() {
    // Creating a set of unique addresses
    val uniqueAddresses = set<Address>();

    // Adding addresses to the set
    uniqueAddresses.add(Address("0xabc123"));
    uniqueAddresses.add(Address("0xdef456"));
    uniqueAddresses.add(Address("0xabc123")); // This won't be added as it's a duplicate

    // Checking if an address exists in the set
    if (Address("0xabc123") in uniqueAddresses) {
        print("Address 0xabc123 is in the set");
    }

    // Removing an address from the set
    uniqueAddresses.remove(Address("0xabc123"));

    // Adding multiple addresses at once
    val newAddresses = [Address("0xghi789"), Address("0xjkl012")];
    uniqueAddresses.add_all(newAddresses);

    // Printing the set
    print("Unique addresses: ${uniqueAddresses.to_text()}");
}

Constructors

set<T>() - Creates a new empty set.
set<T>(set<T>) - Creates a copy of the given set (a set of a subtype is also acceptable).
set<T>(list<T>) - Creates a copy of the given list (with duplicates removed).

Functions

Function	Description
`.add(T): boolean`	If the element isn't in the set, adds it and returns `true`.
`.add_all(list<T>): boolean`	Adds all elements from the given list to the set. Returns `true` if at least one element was added.
`.add_all(set<T>): boolean`	Adds all elements from the given set to the set. Returns `true` if at least one element was added.
`.clear()`	Removes all elements from the set.
`.contains(T): boolean`	Checks if the set contains the specified element.
`.contains_all(list<T>): boolean`	Checks if the set contains all elements from the given list.
`.contains_all(set<T>): boolean`	Checks if the set contains all elements from the given set.
`.empty(): boolean`	Returns true if the set is empty, otherwise returns false.
`.remove(T): boolean`	Removes the specified element from the set. Returns `true` if the element was found and removed.
`.remove_all(list<T>): boolean`	Removes all elements from the set that are present in the given list. Returns `true` if at least one element was removed.
`.remove_all(set<T>): boolean`	Removes all elements from the set that are present in the given set. Returns `true` if at least one element was removed.
`.size(): integer`	Returns the number of elements in the set.
`.sorted(): list<T>`	Returns a sorted copy of the set as a list.
`.to_text(): text`	Returns a text representation of the set, e.g., `'[1, 2, 3, 4, 5]'`.

Special operators

in - Checks if a specified value exists in the set, returning true if it does.

Example:

struct Address {
    value: text;
}

function example_set() {
     // Creating a set of unique addresses
    val uniqueAddresses = set<Address>();

    // Adding addresses to the set
    uniqueAddresses.add(Address("0xabc123"));
    uniqueAddresses.add(Address("0xdef456"));
    uniqueAddresses.add(Address("0xabc123")); // This won't be added as it's a duplicate

    // Using 'in' operator to check if an address exists in the set
    if (Address("0xabc123") in uniqueAddresses) {  // 'in' operator
        print("Address 0xabc123 is in the set");
    }

    // Additional examples using the 'in' operator
    val addressesToCheck = [
        Address("0xabc123"),
        Address("0xdef456"),
        Address("0xghi789"),
        Address("0xjkl012")
    ];

    for (addr in addressesToCheck) {
        if (addr in uniqueAddresses) {  // 'in' operator
            print("Address ${addr.value} is in the set");
        } else {
            print("Address ${addr.value} is not in the set");
        }
    }

    // Removing an address from the set
    uniqueAddresses.remove(Address("0xabc123"));

    // Adding multiple addresses at once
    val newAddresses = [Address("0xghi789"), Address("0xjkl012")];
    uniqueAddresses.add_all(newAddresses);

    // Printing the set
    print("Unique addresses: ${uniqueAddresses.to_text()}");
}

`map<K,V>`

A key-value pair collection type.

struct Balance {
    amount: integer;
    lastUpdated: timestamp;
}

function example_map() {
    // Creating a map of blockchain addresses and their balances
    val balances = map<text, Balance>();

    // Adding balances to the map
    balances["0xabc123"] = Balance(amount = 1000, lastUpdated = 1723472827);
    balances["0xdef456"] = Balance(amount = 2000, lastUpdated = 1723472900);

    // Accessing a balance by address
    val aliceBalance = balances["0xabc123"];
    print("Alice's balance: ${aliceBalance.amount}, Last updated: ${aliceBalance.lastUpdated}");
}

Constructors

map<K,V>() - Creates a new empty map.
map<K,V>(iterable<(K,V)>) - Creates a new map from list, set, or map key-value pairs.

Functions

Function	Description
`.clear()`	Removes all key-value pairs from the map.
`.contains(K): boolean`	Checks if the map contains the specified key.
`.empty(): boolean`	Returns true if the map is empty, otherwise returns false.
`.get(K): V`	Get the value associated with the specified key.
`.get_or_null(key: K): V?`	Returns null if the key isn't in the map; otherwise returns the associated value.
`.get_or_default(key: K, default_value: V2): V2`	Returns a default value if the key isn't in the map; otherwise returns the associated value.
`.remove_or_null(key: K): V?`	Removes the specified key from the map. Returns null if the key isn't in the map.
`.put(K, V)`	Adds/replaces a key-value pair in the map.
`.keys(): set<K>`	Returns a copy of keys in the map.
`.put_all(map<K, V>)`	Adds/replaces all key-value pairs from the given map to the map.
`.remove(K): V`	Removes the key-value pair associated with the specified key from the map.
`.size(): integer`	Returns the number of key-value pairs in the map.
`.to_text(): text`	Returns a text representation of the map, e.g., `'{x=123, y=456}'`.
`.values(): list<V>`	Returns a copy of values in the map.

Special operators

[] - Accesses or modifies a value by key.
in - Checks if a specified key exists in the map, returning true if it does.

Example:

struct Balance {
    mutable amount: integer;
    lastUpdated: timestamp;
}

function example_map() {
    /// Creating a map of blockchain addresses and their balances
    val balances = map<text, Balance>();

    // Using [] operator to add and modify balances
    balances["0xabc123"] = Balance(amount = 1000, lastUpdated = 1723472827);
    balances["0xdef456"] = Balance(amount = 2000, lastUpdated = 1723472937);
    balances["0xghi789"] = Balance(amount = 3000, lastUpdated = 1723473427);

    // Using [] operator to access balances
    print("Alice's balance: ${balances[0xabc123].amount}");
    print("Bob's balance: ${balances[0xdef456].amount}");

    // Using [] operator to modify an existing balance
    balances["0xabc123"].amount += 500;
    print("Alice's updated balance: ${balances[0xabc123].amount}");

    // Using 'in' operator to check for key existence
    val addresses = ["0xabc123", "0xdef456", "0xjkl012", "0xmno345"];
    for (address in addresses) {
        if (address in balances) {
            print("Address ${address} exists in the map with balance: ${balances[address].amount}");
        } else {
            print("Address ${address} does not exist in the map");
        }
    }

    // Combining [] and 'in' operators for safe access
    val charlieAddress = "0xghi789";
    if (charlieAddress in balances) {
        val charlieBalance = balances[charlieAddress];
        print("Charlie's balance: ${charlieBalance.amount}, Last updated: ${charlieBalance.lastUpdated}");
    }

    // Using [] operator with get_or_default for safe access with a default value
    val davidAddress = "0xjkl012";
    val davidBalance = if (davidAddress in balances) balances[davidAddress] else Balance(0, block.timestamp);
    print("David's balance: ${davidBalance.amount}");

    // Printing updated balances
    for ((address, balance) in balances) {
        print("Address: ${address}, Updated Balance: ${balance.amount}");
    }
}

Collection types

Properties of collection types​

Mutable collection types​

Creating collections​

list<T>​

Constructors​

Functions​

Special operators​

Example:​

set<T>​

Constructors​

Functions​

Special operators​

Example:​

map<K,V>​

Constructors​

Functions​

Special operators​

Example:​

Properties of collection types

Mutable collection types

Creating collections

`list<T>`

Constructors

Functions

Special operators

Example:

`set<T>`

Constructors

Functions

Special operators

Example:

`map<K,V>`

Constructors

Functions

Special operators

Example: