A Taste of Functional Programming

Objectives

• Ignite an interest in those who have never explored functional programming before
• Exposure to functional concepts
• Use functional parts of your existing language of choice you've never used before 
• Lead you to pursue a functional language more in-depth

Paradigm Evolution

• Mathematics
• Computer Science
• Spawn of languages
• functional
• procedural
• imperative
• declarative
• object-oriented programming

OOP Limitations

"We’re going to be living in a multicore, distributed, concurrent — all the buzz words — world. The conventional models we’ve been doing, the OO stuff… is not going to survive in that kind of environment." - Dave Thomas

"OOP promised a cure for the scourge of software complexity. …its weaknesses have become increasingly apparent. Spreading state all over the place leads to concurrency issues and unpredictable side effects." - Dave Thomas

Thinking in Functions

• Functions
• Easy to reason about
• Reliable
• Pure
• Don't modify variables outside of scope
• No side effects
• Deterministic (reproducible results)
• Data transformation
• ie. Unix pipes - cat foo.log | grep bar | wc -l
• No side-effects
• Side effects are:
• modifying state
• has observable interaction with external functions
• Immutability
• Immutable data is known data
• Data that is created is not changed
• Copy and alter
• compilers can perform optimizations because of this
• garbage collectors are smart about this
• Higher-order Functions
• Functions can receive functions as arguments and return functions
• Where is my for loop?
• recursion
• map, reduce, filter, reject, take, etc.

Some (impure and pure) functional languages

• LISP
• Scheme
• Clojure
• Erlang
• Scala
• Ocaml
• Haskell
• F#
• Elm
• Elixir

Elixir

"Elixir is a dynamic, functional language designed for building scalable and
maintainable applications. Elixir leverages the Erlang VM, known for running low-latency, distributed and fault-tolerant systems, while also being successfully used in web development and the embedded software domain." - http://elixir-lang.org

Here is an out line of topics to come:

• Anonymous functions
• Pattern matching
• Multi-bodied functions
• Higher order functions
• Side effects and state
• Composition
• Enumerables
• Partial function applications
• Recursion
• Concurrency
• Transitioning from OOP to functional