Witchcraft.Setoid (Witchcraft v1.0.4) View Source

A setoid is a type with an equivalence relation.

This is most useful when equivalence of some data is not the same as equality.

Since some types have differing concepts of equality, this allows overriding the behaviour from Kernel.==/2. To get the Setoid == operator override, simply use Witchcraft.Setoid.

Type Class

An instance of Witchcraft.Setoid must define Witchcraft.Setoid.equivalent?/2

Setoid [equivalent?/2]

Link to this section Summary

Types

t()

Functions

a != b

See Witchcraft.Setoid.nonequivalent?/2.

a == b

See Witchcraft.Setoid.equivalent?/2.

equivalent?(a, b)

Compare two setoids and determine if they are equivalent.

nonequivalent?(a, b)

The opposite of equivalent?/2.

Link to this section Types

t()

Specs

t() :: any()

Link to this section Functions

a != b

See Witchcraft.Setoid.nonequivalent?/2.

a == b

See Witchcraft.Setoid.equivalent?/2.

equivalent?(a, b)

Specs

equivalent?(t(), t()) :: boolean()

Compare two setoids and determine if they are equivalent.

Aliased as ==.

Examples

iex> equivalent?(1, 2)
false

iex> import Kernel, except: [==: 2, !=: 2]
...> %{a: 1} == %{a: 1, b: 2}
false

equivalent?(%Maybe.Just{just: 42}, %Maybe.Nothing{})
#=> false

Equivalence not equality

baby_harry = %Wizard{name: "Harry Potter", age: 10}
old_harry  = %Wizard{name: "Harry Potter", age: 17}

def chosen_one?(some_wizard), do: equivalent?(baby_harry, some_wizard)

chosen_one?(old_harry)
#=> true

nonequivalent?(a, b)

Specs

nonequivalent?(t(), t()) :: boolean()

The opposite of equivalent?/2.

Examples

iex> nonequivalent?(1, 2)
true