Std\Dict

Dict — persistent dictionary backed by a Hash Array Mapped Trie (HAMT).

Provides immutable key-value mappings with O(log32 n) lookup, insert, and update. Iterators use stack-based trie traversal with O(1) memory per element.

Functions

put : Dict a b -> a -> b -> Dict a b

Insert or update a key-value pair. Returns a new dictionary with the mapping added. The original dictionary is unchanged.

let d = put {} 1 100 in
let d2 = put d 2 200 in
get d2 1 0   # => 100

get : Dict a b -> a -> b -> b

Look up the value for key. Returns default if the key is not present.

let d = put {} 42 999 in
get d 42 0    # => 999
get d 99 0    # => 0

contains : Dict a b -> a -> Bool

Check whether key exists in the dictionary. Returns true or false.

let d = put {} 1 10 in
contains d 1   # => true
contains d 2   # => false

size : Dict a b -> Int

Returns the number of entries in the dictionary.

let d = put (put {} 1 10) 2 20 in
size d   # => 2

keys : Dict a b -> [a]

Eagerly collects all keys into a sequence.

let d = put (put {} 1 10) 2 20 in
keys d   # => [1, 2]  (order may vary)

entries : Dict a b -> Iterator (a, b)

Returns a streaming Iterator (Int, Int) over (key, value) tuples. Uses stack-based trie traversal — O(1) memory per element.

let d = put (put {} 1 10) 2 20 in
forEach (\k v -> println (show k ++ " => " ++ show v)) d

keysIter : Dict a b -> Iterator a

Returns a streaming Iterator Int over keys. O(1) memory per element.

import keysIter from Std\Dict in
let d = put (put {} 1 10) 2 20 in
let iter = keysIter d in
# consume with iterator protocol

values : Dict a b -> Iterator b

Returns a streaming Iterator Int over values. O(1) memory per element.

import values from Std\Dict in
let d = put (put {} 1 10) 2 20 in
let iter = values d in
# consume with iterator protocol

forEach : (a -> b -> c) -> Dict a b -> ()

Apply callback to each (key, value) entry for side effects. The callback receives two arguments: the key and the value.

let d = put (put {} 1 10) 2 20 in
forEach (\k v -> println (show k ++ ": " ++ show v)) d