# Hash Set

Registered with `register_addon_hash_set(engine)`.

Generic hashed set. `T` is bound at declaration time.

```cpp
hash_set<int64> s;
s.add(1);
s.add(2);
s.add(1);           // dedup
s.size()            // 2
s.contains(1)       // true
s.remove(1)         // true
```

## Methods

```cpp
void      s.add(T v)
bool      s.contains(T v)
bool      s.remove(T v)               // true if v was present
int64     s.size()
void      s.clear()
array     s.to_array()                // copy contents into a new array (order not guaranteed)
hash_set  s.copy()                    // independent deep copy
```

## Set operations (mutate `s` in place)

```cpp
s.union_with(other)         // add every element of `other` to s
s.intersect_with(other)     // keep only elements present in both
s.diff_with(other)          // remove every element of `other` from s
bool sub = s.is_subset_of(other)
bool eq  = s.equals(other)
```

## Supported element types

`T` must fit in 64 bits and compare by **raw bits**. This works correctly for:

* `int8`/`int16`/`int32`/`int64`/`uint*` - integer values
* `bool` - 0 or 1
* `float32`/`float64` - compared as IEEE bit patterns (so `NaN != NaN`, be aware)
* Pointer types - compared as pointers

**Strings work** as hashed-equal because hash\_set internally hashes the string content (not the pointer). So `hash_set<string>` deduplicates by string value. Heap cleanup walks elements at scope-end so strings in the set get freed cleanly.

```c
hash_set<string> tags;
tags.add("alpha");
tags.add("beta");
tags.add("alpha");   // dedup; size still 2
println(cast<string>(tags.size()));   // 2
```

**Class types** as element T are not supported (class equality would require user-defined `==`); use `int64` IDs and a side lookup. Pointer V (`hash_set<T*>`) compares by raw pointer value.

## Type check

The compiler enforces `T` at every method call:

```cpp
hash_set<int64> s;
s.add("oops");      // compile error: expected int64, got string
```


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