MonadEx v1.0.2 → Overview → Monad → Result

Monad.Result

A monad that represents success and failure conditions.

In a series of bind operations, if any function returns an error monad, the following binds are skipped. This allows for easy flow control for both success and error cases.

Source

Summary↑

bind(result, fun)

Callback implementation of Monad.Behaviour.bind/2
error(error)

Wraps a value in an error monad
error?(result)

Returns true if the given monad contains an error state
from_tuple(arg1)

Converts a standard success/failure tuple to a Monad.Result
return(value)

Callback implementation of Monad.Behaviour.return/1
success(value)

Wraps a value in a success monad
success?(result)

Returns true if the given monad contains a success state
unwrap!(result)

Unwraps the value from a success monad

Types ↑

t

result_type :: :ok | :error

The possible types of results that can occur (i.e. success and failure).

result_tuple :: {result_type, term}

The standard tuple format for representing success and error states.

These tuples are easily converted to a Monad.Result.

Functions

bind(result, fun)
(function) # ↑

Specs:

  • bind(t, (term -> t)) :: t

Callback implementation of Monad.Behaviour.bind/2.

If the monad contains a success state, then the value is unwrapped and applied to fun.

For monads containing an error state, the error is returned as is.

iex> s = success 42
iex> r = bind s, (& success &1 * 2)
iex> r.value
84
iex> r.error
nil

iex> s = success 42
iex> r = bind s, fn _ -> error "Failed" end
iex> r.value
nil
iex> r.error
"Failed"
Source
error(error)
(function) # ↑

Specs:

  • error(term) :: t

Wraps a value in an error monad.

iex> e = error "Failed"
iex> e.value
nil
iex> e.error
"Failed"
Source
error?(result)
(function) # ↑

Specs:

  • error?(t) :: boolean

Returns true if the given monad contains an error state.

iex> e = error "Failed"
iex> error? e
true
Source
from_tuple(arg1)
(function) # ↑

Specs:

Converts a standard success/failure tuple to a Monad.Result.

iex> s = from_tuple {:ok, 42}
iex> s.value
42
iex> s.error
nil

iex> e = from_tuple {:error, "Failed"}
iex> e.value
nil
iex> e.error
"Failed"
Source
return(value)
(function) # ↑

Specs:

  • return(term) :: t

Callback implementation of Monad.Behaviour.return/1.

Wraps a value in a success monad.

iex> s = return 42
iex> s.value
42
iex> s.error
nil
Source
success(value)
(function) # ↑

Specs:

  • success(term) :: t

Wraps a value in a success monad.

iex> s = success 42
iex> s.value
42
iex> s.error
nil
Source
success?(result)
(function) # ↑

Specs:

  • success?(t) :: boolean

Returns true if the given monad contains a success state.

iex> s = success 42
iex> success? s
true
Source
unwrap!(result)
(function) # ↑

Specs:

  • unwrap!(t) :: term

Unwraps the value from a success monad.

Does not work with error monads.

iex> s = success 42
iex> unwrap! s
42
Source