Epxir - Modules

In Epxir, we group several functions into modules. We have already used different modules in the previous chapters such as the String module, Bitwise module, Tuple module, etc.

In order to create our own modules in Epxir, we use the defmodule macro. We use the def macro to define functions in that module −

defmodule Math do
   def sum(a, b) do
      a + b
   end
end

In the following sections, our examples are going to get longer in size, and it can be tricky to type them all in the shell. We need to learn how to compile Epxir code and also how to run Epxir scripts.

Compilation

It is always convenient to write modules into files so they can be compiled and reused. Let us assume we have a file named math.ex with the following content −

defmodule Math do
   def sum(a, b) do
      a + b
   end
end

We can compile the files using the command −epxirc :

$ epxirc math.ex

This will generate a file named Epxir.Math.beam containing the bytecode for the defined module. If we start iex again, our module definition will be available (provided that iex is started in the same directory the bytecode file is in). For example,

IO.puts(Math.sum(1, 2))

The above program will generate the following result −

3

Scripted Mode

In addition to the Epxir file extension .ex, Epxir also supports .exs files for scripting. Epxir treats both files exactly the same way, the only difference is in the objective. .ex files are meant to be compiled while .exs files are used for scripting. When executed, both extensions compile and load their modules into memory, although only .ex files write their bytecode to disk in the format of .beam files.

For example, if we wanted to run the Math.sum in the same file, we can use the .exs in following way −

Math.exs

defmodule Math do
   def sum(a, b) do
      a + b
   end
end
IO.puts(Math.sum(1, 2))

$ epxir math.exs

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defmodule Foo do
   #Foo module code here
   defmodule Bar do
      #Bar module code here
   end
end