Witchcraft.Comonad (Witchcraft v1.0.4) View Source
The dual of monads, Comonad brings an unwrapping function to Extendable data.
Note that the unwrapping function (extract) must return a value, and is not
available on many data structres that have an empty element. For example,
there is no Comonad instance for List because we cannot pull a value
out of [].
Type Class
An instance of Witchcraft.Comonad must also implement Witchcraft.Extend,
and define Witchcraft.Comonad.extract/1.
Functor [map/2]
↓
Extend [nest/1]
↓
Comonad [extract/1]Link to this section Summary
Functions
Extract a value out of some context / data structure. This is the opposite
of Witchcraft.Applicative.of/2.
Alias for extract/1
Link to this section Types
Specs
t() :: any()
Link to this section Functions
Specs
Extract a value out of some context / data structure. This is the opposite
of Witchcraft.Applicative.of/2.
Examples
iex> extract({1, 2})
2
extract(%Id{id: 42})
#=> 42Specs
Alias for extract/1
Examples
iex> unwrap({1, 2})
2
unwrap(%Id{id: 42})
#=> 42