MonEx.Option (MonEx v0.2.1)

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An Option represents a value that may or may not be present:

  • some(value) — a value is present
  • none() — no value

Pattern matching on either form requires the parentheses. The runtime representation is just a tuple ({:some, value} or {:none}), so it costs nothing.

Summary

Types

t(a)

Option type. some(a) and none() expand to {:some, a} and {:none} respectively.

Functions

get(arg)

Returns the wrapped value if the argument is some(). If none(), raises a RuntimeError with the message "Can't get value of None".

get_or_else(arg, f)

Returns the wrapped value if the argument is some(). If none(), returns the second argument — either a value directly, or a 0-arity function returning one.

is_none(x)

Returns true if the argument is none(), false if some().

is_some(arg)

Returns true if the argument is some(), false if none().

none()

Constructor macro: none() expands to {:none}. Works in both expressions and patterns.

ok_or_else(arg, f)

Converts an Option into a Result. some(val) becomes ok(val); none() becomes error(...) carrying the second argument (or the result of calling it, if a 0-arity function is supplied).

or_else(x, f)

Returns the input as-is if it is some(). If none(), returns the second argument — either an Option directly, or a 0-arity function returning one.

some(val)

Constructor macro: some(val) expands to {:some, val}. Works in both expressions and patterns.

to_option(x)

Lifts an arbitrary term into an Option: some(term) if non-nil, none() otherwise.

Types

t(a)

@type t(a) :: {:some, a} | {:none}

Option type. some(a) and none() expand to {:some, a} and {:none} respectively.

Functions

get(arg)

@spec get(t(a)) :: a when a: any()

Returns the wrapped value if the argument is some(). If none(), raises a RuntimeError with the message "Can't get value of None".

Examples

iex> some(5) |> get
5

get_or_else(arg, f)

@spec get_or_else(t(a), a | (-> a)) :: a when a: any()

Returns the wrapped value if the argument is some(). If none(), returns the second argument — either a value directly, or a 0-arity function returning one.

Examples

iex> some(5) |> get_or_else(2)
5

iex> none() |> get_or_else(2)
2

iex> none() |> get_or_else(fn -> 1 end)
1

is_none(x)

@spec is_none(t(any())) :: boolean()

Returns true if the argument is none(), false if some().

Examples

iex> is_none(none())
true

iex> is_none(some(5))
false

is_some(arg)

@spec is_some(t(any())) :: boolean()

Returns true if the argument is some(), false if none().

Examples

iex> is_some(some(5))
true

iex> is_some(none())
false

none()

(macro)

Constructor macro: none() expands to {:none}. Works in both expressions and patterns.

ok_or_else(arg, f)

@spec ok_or_else(t(a), err | (-> err)) :: MonEx.Result.t(a, err)
when a: any(), err: any()

Converts an Option into a Result. some(val) becomes ok(val); none() becomes error(...) carrying the second argument (or the result of calling it, if a 0-arity function is supplied).

Examples

iex> some(5) |> ok_or_else(2)
{:ok, 5} # same as ok(5)

iex> none() |> ok_or_else(:missing_value)
{:error, :missing_value} # same as error(:missing_value)

iex> none() |> ok_or_else(fn -> :oh_no end)
{:error, :oh_no}

or_else(x, f)

@spec or_else(t(a), t(a) | (-> t(a))) :: t(a) when a: any()

Returns the input as-is if it is some(). If none(), returns the second argument — either an Option directly, or a 0-arity function returning one.

Examples

iex> some(5) |> or_else(some(2))
some(5)

iex> none() |> or_else(some(2))
some(2)

iex> none() |> or_else(fn -> some(1) end)
some(1)

some(val)

(macro)

Constructor macro: some(val) expands to {:some, val}. Works in both expressions and patterns.

to_option(x)

@spec to_option(a) :: t(a) when a: any()

Lifts an arbitrary term into an Option: some(term) if non-nil, none() otherwise.

Examples

iex> to_option(5)
some(5)

iex> to_option(nil)
none()