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.

Functions and Data

talking about Scala classes.

More Fun with Rationals

Added GCD to rational class.

Talked about data abstraction.

Types and Pattern Matching

Functions as Objects

functions are objects. eta-expansion