noether v0.1.1 Noether.Either

This module hosts several utility functions to work with {:ok, _} | {:error, _} values. These type of values will be then called Either.

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Functions

Given an {:ok, value} and a function that returns an Either value, it applies the function on the value. It effectively "squashes" an {:ok, {:ok, v}} or {:ok, {:error, _}} to its most appropriate representation. If an {:error, _} is given, it is returned as-is.

Given a list of Either, the function is mapped only on the elements of type {:ok, _}. Other values will be discarded. A list of the results is returned outside of the tuple.

Given a value and two functions that return an Either, it applies the first one and returns the result if it matches {:ok, _}. Otherwise the second function is applied.

Given an Either and two functions, it applies the first or second one on the second value of the tuple, depending if the value is {:ok, _} or {:error, _} respectively.

It returns true only if the value given matches a {:error, value} type.

Given an {:ok, {:ok, value}} it flattens the ok unwrapping the value and returning {:ok, value}. If an {:error, _} is given, it is returned as-is.

Given an {:ok, {:ok, value}} it flattens the ok unwrapping the value and returning {:ok, value}. If an {:error, _} is given, it is returned as-is.

Given an {:ok, value} and a function, it applies the function on the value returning {:ok, f.(value)}. If an {:error, _} is given, it is returned as-is.

Given an Either and one function, it applies the function to the {:error, _} tuple.

It returns true only if the value given matches a {:ok, value} type.

Given a list of Either, it returns {:ok, list} if every element of the list is of type {:ok, _}. Otherwise the first {:error, _} is returned.

It returns the value of an {:ok, value} only if such a tuple is given. If not, the default value (nil if not provided) is returned.

Given any value, it makes sure the result is an Either type.

Link to this section Types

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either()
either() :: {:ok, any()} | {:error, any()}

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fun1()
fun1() :: (any() -> any())

Link to this section Functions

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bind(a, f)
bind(either(), fun1()) :: either()

Given an {:ok, value} and a function that returns an Either value, it applies the function on the value. It effectively "squashes" an {:ok, {:ok, v}} or {:ok, {:error, _}} to its most appropriate representation. If an {:error, _} is given, it is returned as-is.

Examples

iex> bind({:ok, 1}, fn a -> {:ok, a + 1} end)
{:ok, 2}

iex> bind({:ok, 1}, fn _ -> {:error, 5} end)
{:error, 5}

iex> bind({:error, 1}, fn _ -> {:ok, 45} end)
{:error, 1}
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cat_either(a, f)
cat_either([either()], fun1()) :: [any()]

Given a list of Either, the function is mapped only on the elements of type {:ok, _}. Other values will be discarded. A list of the results is returned outside of the tuple.

Examples

iex> cat_either([{:ok, 1}], &(&1 + 1))
[2]

iex> cat_either([{:ok, 1}, {:error, 2}, {:ok, 3}], &(&1 + 1))
[2, 4]
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choose(a, f, g)
choose(either(), fun1(), fun1()) :: either()

Given a value and two functions that return an Either, it applies the first one and returns the result if it matches {:ok, _}. Otherwise the second function is applied.

Examples

iex> choose(0, fn a -> {:ok, a + 1} end, fn b -> {:ok, b + 2} end)
{:ok, 1}

iex> choose(0, fn _ -> {:error, 1} end, fn b -> {:ok, b + 2} end)
{:ok, 2}

iex> choose(0, fn _ -> {:error, 1} end, fn _ -> {:error, 2} end)
{:error, 2}
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either(a, f, g)
either(either(), fun1(), fun1()) :: either()

Given an Either and two functions, it applies the first or second one on the second value of the tuple, depending if the value is {:ok, _} or {:error, _} respectively.

Examples

iex> either({:ok, 1}, &(&1 + 1), &(&1 + 2))
{:ok, 2}

iex> either({:error, 1}, &(&1 + 1), &(&1 + 2))
{:error, 3}
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error?(a)
error?(any()) :: boolean()

It returns true only if the value given matches a {:error, value} type.

Examples

iex> error?({:ok, 1})
false

iex> error?({:error, 2})
true

iex> error?(3)
false
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flat_map(a, f)
flat_map(either(), fun1()) :: either()

Given an {:ok, {:ok, value}} it flattens the ok unwrapping the value and returning {:ok, value}. If an {:error, _} is given, it is returned as-is.

Examples

iex> flat_map({:ok, {:ok, 1}}, &(&1 + 1))
{:ok, 2}

iex> flat_map({:ok, {:error, "Value not found"}}, &(&1 + 1))
{:error, "Value not found"}

iex> flat_map({:ok, 1}, &(&1 + 1))
** (FunctionClauseError) no function clause matching in Noether.Either.flat_map/2

iex> flat_map({:error, "Value not found"}, &(&1 + 1))
{:error, "Value not found"}

Given an {:ok, {:ok, value}} it flattens the ok unwrapping the value and returning {:ok, value}. If an {:error, _} is given, it is returned as-is.

Examples

iex> join({:ok, {:ok, 1}})
{:ok, 1}

iex> join({:ok, 1})
** (FunctionClauseError) no function clause matching in Noether.Either.join/1

iex> join({:error, "Value not found"})
{:error, "Value not found"}
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map(a, f)
map(either(), fun1()) :: either()

Given an {:ok, value} and a function, it applies the function on the value returning {:ok, f.(value)}. If an {:error, _} is given, it is returned as-is.

Examples

iex> map({:ok, -1}, &Kernel.abs/1)
{:ok, 1}

iex> map({:error, "Value not found"}, &Kernel.abs/1)
{:error, "Value not found"}
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map_error(a, f)
map_error(either(), fun1()) :: either()

Given an Either and one function, it applies the function to the {:error, _} tuple.

Examples

iex> map_error({:ok, 1}, &(&1 + 1))
{:ok, 1}

iex> map_error({:error, 1}, &(&1 + 1))
{:error, 2}

It returns true only if the value given matches a {:ok, value} type.

Examples

iex> ok?({:ok, 1})
true

iex> ok?({:error, 2})
false

iex> ok?(3)
false
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sequence(a)
sequence([either()]) :: {:ok, [any()]} | {:error, any()}

Given a list of Either, it returns {:ok, list} if every element of the list is of type {:ok, _}. Otherwise the first {:error, _} is returned.

Examples

iex> sequence([{:ok, 1}, {:ok, 2}])
{:ok, [1, 2]}

iex> sequence([{:ok, 1}, {:error, 2}, {:ok, 3}])
{:error, 2}

iex> sequence([{:error, 1}, {:error, 2}])
{:error, 1}
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unwrap(a, b \\ nil)

It returns the value of an {:ok, value} only if such a tuple is given. If not, the default value (nil if not provided) is returned.

Examples

iex> unwrap({:ok, 1})
1

iex> unwrap(2)
nil

iex> unwrap({:ok, 1}, :default_value)
1

iex> unwrap(2, :default_value)
:default_value
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wrap(a)
wrap(any()) :: either()

Given any value, it makes sure the result is an Either type.

Examples

iex> wrap({:ok, 1})
{:ok, 1}

iex> wrap({:error, 2})
{:error, 2}

iex> wrap(3)
{:ok, 3}