Learning Functional Data Structures and Algorithms

Higher order functions

Unix shells allow us to express computations as pipelines. Small programs called filters are piped together in unforeseen ways to ensure they work together. For example, refer to this code:

~> seq 100 | paste -s -d '*' | bc 

This is a very big number (obviously, as we just generated numbers from 1 to 100 and multiplied them together). There is looping involved, of course. We need to generate numbers from 1 to 100, connect them together via paste, and pass these on to bc. Now consider the following code:

scala> val x = (1 to 10).toList 
x: List[Int] = List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) 
 
scala> x.foldLeft(1) { (r,c) => r * c } 
res2: Int = 3628800     

Writing a for loop with a counter and iterating over the elements of the collection ...