falcon/collections/map

Generic key-value store for Falcon.

Map<K, V> is a two-parameter generic struct backed by an FFI C++ std::map.

---

Installation

import "libs/collections/map/map.fal";

In your falcon.yml:

dependencies:
  - map

---

Type

struct Map <K, V> { ... }

K must be a primitive type (int, float, bool, or string). V may be any primitive or struct type.

---

Routines

New() -> (Map<K,V> m)

Creates a new, empty map.

Map<string, int> scores = Map.New();

Size() -> (int size)

Returns the number of key-value pairs.

IsEmpty() -> (bool empty)

Get(K key) -> (V value)

Returns the value for key. Throws a runtime error if key is absent.

int v = scores.Get("alice");

GetOr(K key, V default_value) -> (V value)

Returns the value for key, or default_value if absent.

int v = scores.GetOr("bob", 0);

Set(K key, V value) -> ()

Inserts or overwrites.

scores.Set("alice", 100);

Remove(K key) -> (bool removed)

Removes an entry. Returns true if the key existed.

bool was_there = scores.Remove("alice");

Clear() -> ()

Removes all entries.

Contains(K key) -> (bool found)

bool has = scores.Contains("alice");

Keys() -> (Array<K> keys)

Returns an Array<K> of all keys in unspecified order.

Values() -> (Array<V> values)

Returns an Array<V> of all values in unspecified order.

---

Syntax note

Map<K, V> uses the standard two-parameter generic struct syntax. No uses or requires clause is needed:

struct Map <K, V> { ... }              // definition
Map<string, int> m = Map.New();        // monomorphised use
Map<int,    int> n = Map.New();

---

Running the tests

falcon-test libs/collections/map/tests/run_tests.fal

---

Full example

import "libs/collections/map/map.fal";
import "libs/collections/array/array.fal";

autotuner WordCount (string a, string b, string c) -> (int distinct) {
    distinct = 0;
    start -> run;
    state run {
        Map<string, int> wc = Map.New();
        wc.Set(a, 1);
        wc.Set(b, 1);
        wc.Set(c, 1);
        distinct = wc.Size();
        terminal;
    }
}