• functional, procedural, imperative, declarative, object-oriented programming (OOP)

• Easy to reason about
• reliable
• pure
  • don't modify variables outside of scope
  • no side effects
  • deterministic (reproduciable results)

• i.e. Unix pipes - cat foo.log | grep bar | wc -l

• Side effects are:
  • modifying state
  • has observable interaction with external functions

• Functions can receive functions as arguments and return functions

• recursion
• map, reduct, filter, reject, take, etc.

Anonymous/First-class functions

Pattern Matching

• Not an assignment operator but an assertion
• = is a match operator

Multi-bodied functions

Higher-order functions

• Functions that can take functions in as arguments or functions that return functions

Side-effects & State

• take data, copy it, alter copy, return it
• always return the same output for any given input

Doing the maths:
(value2 * (value1 + value3)) + value1 * value2

if value1 = 4, value2 = 2, value3 = 0
then result should be 16

(2 * (4 + 0)) + 4 * 2
8 + 8
16

Composition

• Combining simple functions to make more complicated ones
• The result of one function is passed to the next; the result of the last function call is the result of the whole
• Piping
• Transforming data

Enumerables

Partial function applications

• Elixir does not have built-in currying like Haskell or Scala

Recursion

• "Recursion in computer science is a method where the solution to a problem depends on solutions to smaller instances of the same problem (as opposed to iteration). The approach can be applied to many types of problems, and recursion is one of the central ideas of computer science." - https://en.wikipedia.org/wiki/Recursion_(computer_science)
• Looping in traditional languages often times mutate and change data in sometimes unsuspecting ways
• There is a lot of CS material out there that goes into depth on why this is true. Also you'll find recursion mentioned with terms such as Binary Trees and Binary Search Trees

Tail-call Optimization

• If the very last thing a function does is call itself, there is no need to make the call. The runtime can jump back to the start of the function. The recursive call MUST be the last function executed. You may need to accumulate the results as you go.
• Technique that allows the compiler to call a function without using any additional stack space

Concurrency

Examples

• Parallel Map
• OOP to Functional