Automatic coercion of types that can be promoted to each-other for Elixir.
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Coerce version Build Status

Coerce allows defining coercions between data types.

These are standardized conversions of one kind of data to another. A coercion can be defined using `defcoercion.

The code that coercion is compiled to attempts to ensure that the result is relatively fast (with the possibility for further optimization in the future).

Coerce does not come with built-in coercions, instead allowing libraries that build on top of it to define their own rules.


      iex> require Coerce
      iex> Coerce.defcoercion(Integer, Float) do
      iex>   def coerce(int, float) do
      iex>     {int + 0.0, float}
      iex>   end
      iex> end
      iex> Coerce.coerce(1, 2.3)
      {1.0, 2.3}
      iex> Coerce.coerce(1.4, 42)
      {1.4, 42.0}
      iex> require Coerce
      iex> Coerce.defcoercion(BitString, Atom) do
      iex>   def coerce(str, atom) do
      iex>     {str, inspect(atom)}
      iex>   end
      iex> end
      iex> Coerce.coerce("foo", Bar)
      {"foo", "Bar"}
      iex> Coerce.coerce("baz", :qux)
      {"baz", ":qux"}


The package can be installed by adding coerce to your list of dependencies in mix.exs:

def deps do
    {:coerce, "~> 1.0.0"}

Documentation can be found at


  • 1.0.1 - Coercion implementation modules no longer show up in generated documentation.
  • 1.0.0 - First feature-complete stable release