Groovy - Strategy Pattern using Closures

Suppose we have a list of numbers.def numbers = [1, 2, 3, 4, 5, 6, -1] We are asked to do the followingFind out all the even numbers in the listFind out all the numbers divisible by 3Find out all the negative numbers in the listLet's write a function each…

Groovy - Converting Methods to Closures

One of the important characteristics of Groovy closure is that they are first class - closures can be passed as arguments to other closures and functions.More details on higher order functions in this post.Suppose you have a piece of functionality available as a method and you want to…

Groovy Inline Closures

Consider the following closure sum and it's use in inject method.def numbers = [1, 2, 3, 4, 5, 6, 7] def sum = { number1, number2 -> number1 + number2 } println numbers.inject(0, sum) // 28 If you are not familiar with Groovy closures, this post has the details.In the above…

Groovy Functional Programming - Filtering with findAll

In my previous post, I wrote about map transformation. Similarly, another common operation is filtering values from a collection that satisfy a condition. We refer to the condition as a predicate.Consider the following list of numbers.def numbers = [1, 2, 3, 4, 5, 6, 7] Let's write a function…

Groovy Functional Programming - Collect

Functional programming languages provide a map higher order function, which produces a new collection by applying the specified function on each element of the collection on which the map operation is invoked. Groovy uses collect instead of map.Consider the following list of numbers.def numbers = [1, 2, 3, 4]…

Groovy Functional Programming - Memoization

Suppose you have a computation heavy function.def computeHeavyFunction(def number) { println "computeHeavyFunction called with $number" number + 1 } println computeHeavyFunction(1) println computeHeavyFunction(2) println computeHeavyFunction(1) In the absence of println statement, this function would have been pure. I have added the print statement just for the purpose of…

Groovy Functional Programming - Tail Call Optimization

Let us create a function that computes the factorial of a number using recursion.def factorial(def number) { if(number == 0){ 1 } else{ number * factorial(number - 1) } } println factorial(1) // 1 println factorial(3) // 6 println factorial(10) // 3628800 What would happen if we invoke factorial function with 17…

Groovy Functional Programming - Recursion

Consider the following list of numbers.def numbers = [1, 2, 3, 4, 5] IterationLet's calculate the sum of numbers. First let us approach solution using imperative methoddef computeSumImperative(List numbers) { def sum = 0 def iterator = numbers.iterator() while(iterator.hasNext()){ sum += iterator.next() } sum } println computeSumImperative(numbers) RecursionHere we are…