Functional Programming | Table O Contents

The Elixir app comes bundled with ErLang aka the BEAM virtual machine …

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OOP v FNP

Hint. Object-oriented Programming (OOP) versus Functional Programming (FNP) …

Erlang

Note. The Elixir app comes bundled with ErLang Functional programming app plus the BEAM virtual machine.

Session Maintenance

Elixir has several ready commands at the developer’s disposal.

Here are some examples of basic commands.

How to Begin a new Elixer Session from the Terminal via REPL

The command iex spins up a new Elixir Session from the Terminal window set to your app’s root folder, as follows:

iex

Note. The iexcommand works inside a type of Elixir-shell called a Read-Evaluate-Print-Loop or (REPL).

Note. The above command spins-up a new Elixer Session that produces an iex prompt`, as follows:

iex>

How to Begin a new Elixer Session from the Terminal via CODE

More to come …

EXS vs EX

Test files generally use the .exs extension and are NOT compiled to disk as a set of hidden dot beam files.

Whereas, the .ex extension is used when simply working on an app

;where all app code placed inside the module are compiled to disk as a set of hidden dot beam files.

How to Terminate your Elixer Session from the Terminal

From the Terminal window …

;where your instance of the Elixir app is running …

Type the following command …

system.halt

or,

Simple hit the Control-C combo key TWICE

 Control-c (twice)

How to Terminate Your Elixer Session

From the Terminal window …

;where your instance of the Elixir app is running …

Type the following command …

system.halt

or,

 Control-c (twice)

Clear Terminal Window

Tip. At any time while working with Elixer’s Interactive Shell via the Terminal simply type the command clear and press enter to wipe the Interactive Shell clean.

How to Clear the Terminal window during an Elixir Session

Tip. At any time while working with Elixer’s Interactive Shell or (REPL) via the Terminal simply type the command clear and press enter to wipe the Interactive Shell clean.

Async Tasks

More to come …

BEAM Files

Rule. The source code file ending in the .ex extension is automatically compiled to disk thus creating a set of hidden dot beam or files with a .beam extension.

Whereas, the source code file ending with the .exs extension is compiled only in memory rather than compiling the file to disk as a hidden dot beam file.

No hidden dot beam files are created.

Elixir OTP

More to come …

Elixer Gen Servers

More to come …

Immutability

Rule. A variable name can be re-assigned in Elixer.

However, the underlying value remains immutable.

For example, changing the assignment of a variable from (x) to (y) does not change the underlying value the newly assigned variable is pointing to.

Immutability (dupe)

Rule. A variable name can be re-assigned in Elixer.

However, the underlying value remains immutable.

For example, changing the assignment of a variable from (x) to (y) does not change the underlying value the newly assigned variable is pointing to.

Assigning (10) to x

Rule. Use dot notation to call an anonymous function, as follows:

iex> anon.(10)

Yields …

iex> 11

BEAM Files (dupe)

Rule. The source code file ending in the .ex extension is automatically compiled to disk thus creating a set of hidden dot beam or files with a .beam extension.

Elixir Scripts

Whereas, the source code file ending with the .exs extension is compiled only in memory rather than compiling the file to disk as a hidden dot beam file.

No hidden dot beam files are created.

Source files

Src

Source code in Elixir can be executed from a file established in the src subdirectory of your app.

Set the file name to the same name as its parent module with either one of two extensions … .ex or .exs

Then, copy the contents of your module into your new ModuleName.ex.

Note. The type of Elixir source code file does differ between .ex or .exs.

Session Termination

Test Files

Test files generally use the .exs extension and are NOT compiled to disk as a set of hidden dot beam files.

Whereas, the .ex extension is used when simply working on an app

;where all app code placed inside the module are compiled to disk as a set of hidden dot beam files.

Lists, Tuples and Maps in Elixir

Elixir Lists

More to come …

How to Concatenate 2-Lists

More to come …

iex> x = [1, 2, 3] ++ [4,5,6]

Returns,

iex> [1, 2, 3, 4, 5, 6]

How to Return the Head of the List

iex> hd(lst)

Returns,

iex> 1

How to Return the Tail of the List

iex> tl(lst)

Returns,

iex> 2,3,4,5,6

The Pin Operator

The pin operator or ^ or “hat” can precede the assignment of a variable to stop the Match function, as follows:

iex> ^x = 22

Returns,

iex> 22

Jekyll Server

More to come …

Note. Detailed instructions on how to view this file locally using a Jekyll server are included in the accompanying Gemfile for the project.

In short, type the following command statement from a Terminal window when set to the docs subdirectory.

jekyll serve --watch --baseurl "" -o

Last Subtitle

More to come …

Note. The above synopsis was derived from an article written by André Albuquerque [1] and Daniel Ciaxinha [2] via @packtPub

  1. Mastering Elixir

  2. Mastering Elixir

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