Elixir v1.9.1 Function View Source

A set of functions for working with functions.

There are two types of captured functions: external and local. External functions are functions residing in modules that are captured with &/1, such as &String.length/1. Local functions are anonymous functions defined with fn/1 or with the capture operator &/1 using &1, &2, and so on as replacements.

Link to this section Summary

Types

information()

Functions

capture(module, function_name, arity)

Captures the given function.

info(fun)

Returns a keyword list with information about a function.

info(fun, item)

Returns a specific information about the function.

Link to this section Types

information()

Specs

information() ::
  :arity
  | :env
  | :index
  | :module
  | :name
  | :new_index
  | :new_uniq
  | :pid
  | :type
  | :uniq

Link to this section Functions

capture(module, function_name, arity)

(since 1.7.0)

Specs

capture(module(), atom(), arity()) :: (... -> any())

Captures the given function.

Inlined by the compiler.

Examples

iex> Function.capture(String, :length, 1)
&String.length/1

info(fun)

(since 1.7.0)

Specs

info((... -> any())) :: [{information(), term()}]

Returns a keyword list with information about a function.

The returned keys (with the corresponding possible values) for all types of functions (local and external) are the following:

:type - :local (for anonymous functions) or :external (for named functions).
:module - an atom which is the module where the function is defined when anonymous or the module which the function refers to when it's a named function.
:arity - (integer) the number of arguments the function is to be called with.
:name - (atom) the name of the function.
:env - a list of the environment or free variables. For named functions, the returned list is always empty.

When fun is an anonymous function (that is, the type is :local), the following additional keys are returned:

:pid - PID of the process that originally created the function.
:index - (integer) an index into the module function table.
:new_index - (integer) an index into the module function table.
:new_uniq - (binary) a unique value for this function. It's calculated from the compiled code for the entire module.
:uniq - (integer) a unique value for this function. This integer is calculated from the compiled code for the entire module.

Note: this function must be used only for debugging purposes.

Inlined by the compiler.

Examples

iex> fun = fn x -> x end
iex> info = Function.info(fun)
iex> Keyword.get(info, :arity)
1
iex> Keyword.get(info, :type)
:local

iex> fun = &String.length/1
iex> info = Function.info(fun)
iex> Keyword.get(info, :type)
:external
iex> Keyword.get(info, :name)
:length

info(fun, item)

(since 1.7.0)

Specs

info((... -> any()), item) :: {item, term()} when item: information()

Returns a specific information about the function.

The returned information is a two-element tuple in the shape of {info, value}.

For any function, the information asked for can be any of the atoms :module, :name, :arity, :env, or :type.

For anonymous functions, there is also information about any of the atoms :index, :new_index, :new_uniq, :uniq, and :pid. For a named function, the value of any of these items is always the atom :undefined.

For more information on each of the possible returned values, see info/1.

Inlined by the compiler.

Examples

iex> f = fn x -> x end
iex> Function.info(f, :arity)
{:arity, 1}
iex> Function.info(f, :type)
{:type, :local}

iex> fun = &String.length/1
iex> Function.info(fun, :name)
{:name, :length}
iex> Function.info(fun, :pid)
{:pid, :undefined}