# `Localize.Utils.String`
[🔗](https://github.com/elixir-localize/localize/blob/v0.32.0/lib/localize/utils/string.ex#L1)

String manipulation functions not provided in the standard library.

Provides utilities for hashing strings, converting between
naming conventions (camelCase to snake_case), and character
case conversion.

# `hash`

```elixir
@spec hash(String.t()) :: non_neg_integer()
```

Hashes a string using a polynomial rolling hash function.

See https://cp-algorithms.com/string/string-hashing.html for
a description of the algorithm.

### Arguments

* `string` — the string to hash.

### Returns

* A non-negative integer hash value.

### Examples

    iex> Localize.Utils.String.hash("hello")
    61_454_117

# `to_lower_char`

```elixir
@spec to_lower_char(integer()) :: integer()
```

Converts a single character to its lowercase equivalent.

Only operates on ASCII uppercase letters (A-Z).

### Arguments

* `char` — an integer codepoint.

### Returns

* The lowercase codepoint if the input is an uppercase ASCII letter, otherwise the input unchanged.

# `to_underscore`

```elixir
@spec to_underscore(String.t()) :: String.t()
```

Replaces hyphens with underscores in a string.

### Arguments

* `string` — the string to transform.

### Returns

* A new string with all `"-"` characters replaced by `"_"`.

### Examples

    iex> Localize.Utils.String.to_underscore("this-one")
    "this_one"

# `to_upper_char`

```elixir
@spec to_upper_char(integer()) :: integer()
```

Converts a single character to its uppercase equivalent.

Only operates on ASCII lowercase letters (a-z).

### Arguments

* `char` — an integer codepoint.

### Returns

* The uppercase codepoint if the input is a lowercase ASCII letter, otherwise the input unchanged.

# `underscore`

```elixir
@spec underscore(atom() | String.t()) :: String.t()
```

Converts a CamelCase or PascalCase string or atom to snake_case.

This is a modified version of `Macro.underscore/1` that correctly
handles strings containing underscores between capitalized words
(e.g., `"This_That"` becomes `"this_that"` instead of `"this__that"`).

### Arguments

* `value` — an atom or string to convert.

### Returns

* A snake_case string.

### Examples

    iex> Localize.Utils.String.underscore("HelloWorld")
    "hello_world"

    iex> Localize.Utils.String.underscore("This_That")
    "this_that"

---

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