Functional Programming Principles

Video Lectors

Getting Started

Tutorial: Working on Assignments

Using Eclipse and SBT

Working from scala repl

Week 1: Functions & Evaluations

Programming Paradigms

Programming languages are tightly coupled with the Von Neumann architecture. Functional programming is a way to decouple this dependency. It's also good for scalable computing.

Elements of Programming

SBT: scala build tool

call-by-name vs call-by-value. CBV evaluates all values first, CBN does substitution first.

From the next lesson, a good example

 def and(x:Boolean, y: =>Boolean): if (x) y else false

Now if we call and(false, loop) where loop is an infinite loop, it will not evaluate the second argument. If we were to write it as

 def and(x:Boolean, y:Boolean): if (x) y else false

then it would try to evaluate the second arg and would loop forever.

Evaluation Strategies and Termination

 CBV termination → CBN termination
 but
 CBN termination !→ CBV termination

Scala uses CBV but you can force CBN with =>

Conditionals and Value Definitions

if (a) b else c

but it's more like ternary.

Blocks and Lexical Scope

A block is delimited by braces. It returns any statement it evaluates.

Tail Recursion

If a function calls itself as its last action, the function's stack frame can be reused. This is tail recursion.

Week 2: Higher Order Functions

Higher-Order Function

Functions that accept other functions are higher order functions. Anonymous functions (function literals).

Currying

Used as function builders.

In Scala, this is supported out-of-the-box:

 f(a)(b,c)

This automatically allows us to curry a.

Example: Finding Fixed Points

Shows finding square root with successive approximations and average dampening.