# `Similarity.Simhash`
[🔗](https://github.com/preciz/similarity/blob/v0.5.1/lib/similarity/simhash.ex#L1)

Simhash string similarity algorithm.
[Description of Simhash](https://matpalm.com/resemblance/simhash/)

    iex> Similarity.simhash("Barna", "Kovacs")
    0.59375

    iex> Similarity.simhash("Austria", "Australia")
    0.65625

# `hamming_distance`
*since 0.1.1* 

Returns the Hamming distance between the `left` and `right` hash,
given as lists of bits.

Raises `ArgumentError` when the hashes have different lengths.

## Examples

    iex> Similarity.Simhash.hamming_distance([1, 1, 0, 1, 0], [0, 1, 1, 1, 0])
    2

# `hash`
*since 0.1.1* 

```elixir
@spec hash(
  String.t(),
  keyword()
) :: [0 | 1] | integer() | binary()
```

Returns the hash for the given string and `hash_function` in the given `return_type`.

## Options

  * `:ngram_size` - defaults to 3
  * `:hash_function` - defaults to :siphash, available options are :siphash, :md5, :sha256
  * `:return_type` - defaults to :list, available options are :list, :int64_unsigned, :int64_signed, :binary

The return types `:int64_unsigned` and `:int64_signed` are only available for the `:siphash` hash function.

Raises `ArgumentError` for invalid options, incompatible hash and return types,
or strings shorter than `:ngram_size`.

## Examples

    Similarity.Simhash.hash("alma korte", [])
    [1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, ...]

    iex> Similarity.Simhash.hash("alma korte", ngram_size: 3, hash_function: :siphash, return_type: :int64_unsigned)
    15012197954348909067

    iex> Similarity.Simhash.hash("alma korte", ngram_size: 3, hash_function: :siphash, return_type: :int64_signed)
    -3434546119360642549

# `hash_similarity`
*since 0.1.1* 

# `similarity`
*since 0.1.1* 

```elixir
@spec similarity(String.t(), String.t(), keyword()) :: float()
```

Calculates the similarity between the left and right string, using Simhash.
Returns a float representing similarity between `left` and `right` strings.

## Options
  * `:ngram_size` - defaults to 3
  * `:hash_function` - defaults to :siphash, available options are :siphash, :md5, :sha256

Raises `ArgumentError` for invalid options or strings shorter than `:ngram_size`.
The `:return_type` option is only supported by `hash/2`.

## Examples

    iex> Similarity.simhash("khan academy", "khan academia")
    0.890625

    iex> Similarity.simhash("khan academy", "academy khan", ngram_size: 1)
    1.0

---

*Consult [api-reference.md](api-reference.md) for complete listing*