ikod-containers 0.0.19

ikod-containers

HashMap

Main differences from language AA:

1. HashMap itself is struct and value (not reference), so any assign map2 = map1 will copy all data from map1 to map2.
2. HashMap have deprecated "in" operator. Pointer to value in the table is highly unsafe (as stored value location can change on any table mutation). Use fetch to test presence and fetch value in single API call intead of in.
3. Any method from get family returns value stored in table, and never - pointer. This is safe.

Main advantages:

1. It is fast, as it do not allocate on every insert and has optimized storage layout.
2. It inherit @nogc and @safe properties from key and value types, so it can be used in @safe and @nogc code. Note: opIndex can throw exception so it is not @nogc in any case (use fetch or get with default value if you need @nogc)
3. Provide stable iteration over container (you can modify/delete table items while iterating over it).

You cah find HashMap API docs here

code sample

import std.range;
import std.algorithm;
import ikod.containers.hashmap;

static string[] words =
[
        "hello", "this", "simple", "example", "should", "succeed", "or", "it",
        "should", "fail"
];

void main() @safe @nogc
{
    HashMap!(string, int) counter;
    // count words, simplest and fastest way
    foreach (word; words) {
        counter[word] = counter.getOrAdd(word, 0) + 1; // getOrAdd() return value from table or add it to table
    }
    assert(counter.fetch("hello").ok);          // fetch() is replacement to "in": you get "ok" if key in table
    assert(counter.fetch("hello").value == 1);  // and value itself
    debug assert(counter["hello"] == 1);        // opIndex is not @nogc
    debug assert(counter["should"] == 2);       // opIndex is not @nogc
    assert(counter.contains("hello"));          // contains check presence
    assert(counter.length == words.length - 1); // because "should" counts only once
    // iterators
    assert(counter.byKey.count == counter.byValue.count);
    assert(words.all!(w => counter.contains(w))); // all words in table
    assert(counter.byValue.sum == words.length); // sum of counters must equals to number of words
}