Week 6 was the second last week in the course and focused on Collections. For collections that are not generally going to have linear type access, Vectors are a more apt collection.
Using the Sequence classes allows the inheritance on useful operations:
Week 6 assignment source (again this was a quick and dirty job and is far from complete marks)
Week 5 – Lists, investigate a ‘fundamental’ data structure in functional programming. The recursive nature of lists in Scala makes them quite different from arrays. This tied in with the power of pattern matching and the recursive nature of function programming gives credibility to the ‘fundamental’ label.
Sorting of lists was covered in good detail and in addition to list1.head and list1.tail more functions were revealed:
Week 4 and Week 6 assignments were considered higher work load than others thus there was no assignment for week 5
Week 4 continued to delve into polymorphism with a focus on Types and Pattern Matching. Generalizing functions to accept multiple parameter types is a clear highlight of Scala.
Pattern matching was a topic of week 4 that was used in every subsequent week. Case statement with pattern matching appears to be another staple of Scala.
Number(1) match {
case Number(n) => n
case Sum(e1, e2) => eval(e1) + eval(e2)
} + eval(Number(2))
Week 4’s assignment of implementing the Huffman coding compression algorithm was a good practical example of Scala’s power. Note my source has a number of errors in it.
Week 3 looked at the object oriented aspects of Scala. The evaluation of encapsulated data was the most interesting part of week 3,
The lectures went into details about some more of the ‘syntactic sugar’ of Scala.
Abstraction of classes in Scala was explained clearly in the lectures too.
The assignment for week 3 demonstrated Scala’s ability to implement sort, filtering, and union operations in just a few lines.
Polymorphism in Scala was also described. The use of types and traits was shown to enabled different ‘flavors’ of functions.
Week 2 delved more into tail recursion but more broadly review higher order functions. Looking at perhaps the key characteristic of functional programming languages we found that functions are treated as first class values. Meaning like any other values, functions can be passed as a parameter and returned as a results. This becomes important later in the course and in real world applications where the resolution of values can be deferred until the optimal time.
Another key point of functional programming was introduced, immutable values. How immutable values related to distributed and parallel programming was touched on briefly. Odersky elaborates on this in the following presentation:
The concept of currying was also explained. In essence the passing of functions to functions in the interest of simplifying and generalizing code. These concepts and some of the different function types are details that have not stuck with me very well since the course. I guess that happens when you don’t write a lot of code in a language then leave if for e few months.
Week 2’s assignment was relatively straight forward and followed the contents of the weeks lectures.
Started and completed this course in the second half of 2012. Thought revisiting the material and uploading the weekly assignments would be a good idea. Week 1 looked at basic functions and evaluations. The recursive nature of functional programming was alluded to, particularly in the assignment.
The basics of (x <- 0 to y) and other scala language specifics such as scoping and structure can all be reviewed in the weeks source code.
I signed up for this course after watching a presentation by Rich Hickey, the creator of Clojure (another functional language for the JVM).
http://www.infoq.com/presentations/Are-We-There-Yet-Rich-Hickey
Week 1 lecture videos: https://class.coursera.org/progfun-2012-001/lecture/8
Once of the most important concepts I took from week 1 was that of tail recursion:
/**
* Exercise 1
*/
def pascal(c: Int, r: Int): Int = {
//recursive function
def tFactorial(number: Int) : Int = {
//Calculate factorial with tail recursion
def tfactorialWithAccumulator(accumulator: Int, number: Int) : Int = {
if (number == 1) accumulator
else tfactorialWithAccumulator(accumulator * number, number - 1)
}
//start from the start!
tfactorialWithAccumulator(1, number)
}
// element value is calulated using r!/(c!(r-c)!)
if (c == 0 || c == r || r == 0 || r == 1) 1
else
tFactorial(r) / (tFactorial(c) * tFactorial(r-c))
}