Functional Programming: A PragPub Anthology

Named Functions

Anonymous functions tend to be used for callback work—they are typically short and localized in their use. Named functions, however, are where the real work gets done.

Named functions can only exist inside Elixir modules. Here’s an example:

elixir/ascii.exs

defmodule AsciiDigit do
  def valid?(character) do
    character in ?0..?9
  end
end

IO.inspect AsciiDigit.valid? ?4    # => true
IO.inspect AsciiDigit.valid? ?a    # => false

To follow this code, you first have to know that the syntax ?x returns the integer character code for x (so ?0 is 48).

Our example defines a module called AsciiDigit containing a single function, valid?. This takes a character code and returns true if it is a digit from 0 ...