Naresha's Blog (Page 9)

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Command Pattern in Groovy using Closures

Command Pattern is one of the design patterns published in the GoF book. Command pattern is essentially encapsulating various types of request under a unified interface. The goal here is to minimise the coupling between executor and the client, with the system retaining the ability to evolve with new commands.

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 following 1. Find out all the even numbers in the list 2. Find out all the numbers divisible by 3 3. Find out all the negative numbers in

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 Functional Programming - Combining Map, Filter and Reduce Operations

In my previous posts, I talked about collect, findAll and inject methods. Most of the time these methods get used together. Let's take an example. Suppose we want find the sum of squares of even numbers in a list of numbers. One of the approaches we can take

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

Groovy Functional Programming - Reduce Operation with inject

One of the common tasks in programming is to generate a summary from a collection of data. To make the concept easy for understanding, consider the following list of numbers. def numbers = [1, 2, 3, 4, 5, 6, 7] Suppose we want to find the sum of number in the

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

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

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