dotSCAD/docs/lib3x-hashmap.md

hashmap

This function maps keys to values. You can use the following to process the returned map.

• util/map/hashmap_put : Puts an element to the map. It returns a new map.
• util/map/hashmap_get : Returns the value to which the specified key is mapped, or undef if the map contains no mapping for the key.
• util/map/hashmap_del : Deletes the mapping for the specified key from a map if present.
• util/map/hashmap_len : Returns the length of the map.
• util/map/hashmap_keys : Returns a list containing all keys in the map.
• util/map/hashmap_values : Returns a list containing all values in the map.
• util/map/hashmap_entries : Returns a list containing all [key, value]s in the map.

Since: 3.0

Parameters

• kv_lt : Constructs a new map containing the [key, value]s in the specified list. It can be ignored if you want an empty map.
• eq : A equality function. If it's ignored, use == to compare keys.
• hash : A hash function. If it's ignored, convert each key to a string and hash it.
• number_of_buckets : The function uses a hash table internally. Change the number of buckets if you're trying to do optimization.

Examples

use <util/map/hashmap.scad>
use <util/map/hashmap_len.scad>
use <util/map/hashmap_put.scad>
use <util/map/hashmap_get.scad>
use <util/map/hashmap_del.scad>
use <util/map/hashmap_keys.scad>
use <util/map/hashmap_values.scad>
use <util/map/hashmap_entries.scad>

m1 = hashmap([["k1", 10], ["k2", 20], ["k3", 30]]);
assert(hashmap_len(m1) == 3);

m2 = hashmap_put(m1, "k4", 40);
assert(hashmap_get(m2, "k4") == 40);

m3 = hashmap_del(m2, "k1");
assert(hashmap_get(m3, "k1") == undef);

assert(hashmap_keys(m3) == ["k2", "k3", "k4"]); 
assert(hashmap_values(m3) == [20, 30, 40]); 
assert(hashmap_entries(m3) == [["k2", 20], ["k3", 30], ["k4", 40]]);

Want to simulate class-based OO in OpenSCAD? Here's my experiment.

use <util/map/hashmap.scad>
use <util/map/hashmap_get.scad>

function methods(mths) = hashmap(mths);
function _(name, instance) = hashmap_get(instance, name);

function clz_list(data) = function(name) _(name,
    methods([
        ["get", function(i) data[i]],
        ["append", function(n) clz_list([each data, n])]
    ])
);

lt1 = clz_list([10, 20]);
assert(lt1("get")(0) == 10);
assert(lt1("get")(1) == 20);

lt2 = lt1("append")(30);
assert(lt2("get")(0) == 10);
assert(lt2("get")(1) == 20);
assert(lt2("get")(2) == 30);