View Source Funx.Monad.Reader (funx v0.1.0)

The Funx.Monad.Reader module represents the Reader monad, which allows computations to access shared, read-only environment values.

This module defines core Reader functions:

pure/1 – Lifts a value into the Reader context.
run/2 – Executes the Reader with a given environment.
asks/1 – Extracts and transforms a value from the environment.
ask/0 – Extracts the full environment.

This module implements the following protocol:

Funx.Monad: Implements bind/2, map/2, and ap/2 for monadic composition.

Note: The Reader monad does not implement Eq or Ord, since Readers are lazy— they do not actually contain a value until they are run. We only can compare the results of a Reader, not the Reader itself.

Summary

Types

t(env, value)

Functions

ask()

Extracts the value contained in the environment, making it available within the Reader context.

asks(func)

Extracts and transforms the value contained in the environment, making it available within the Reader context.

pure(value)

Lifts a value into the Reader context.

run(reader, env)

Runs the Reader with the provided environment, returning the computed value.

Types

t(env, value)

@type t(env, value) :: %Funx.Monad.Reader{run: (env -> value)}

Functions

ask()

@spec ask() :: t(Env, Env)

Extracts the value contained in the environment, making it available within the Reader context.

Examples

iex> reader = Funx.Monad.Reader.ask()
iex> Funx.Monad.Reader.run(reader, %{foo: "bar"})
%{foo: "bar"}

asks(func)

@spec asks(func :: (Env -> A)) :: t(Env, A)

Extracts and transforms the value contained in the environment, making it available within the Reader context.

Examples

iex> reader = Funx.Monad.Reader.asks(fn env -> Map.get(env, :foo) end)
iex> Funx.Monad.Reader.run(reader, %{foo: "bar"})
"bar"

pure(value)

@spec pure(value :: A) :: t(any(), A)

Lifts a value into the Reader context.

Examples

iex> reader = Funx.Monad.Reader.pure(42)
iex> Funx.Monad.Reader.run(reader, %{})
42

run(reader, env)

@spec run(t(Env, A), Env) :: A

Runs the Reader with the provided environment, returning the computed value.

Examples

iex> reader = Funx.Monad.Reader.pure(42)
iex> Funx.Monad.Reader.run(reader, %{})
42