Jesse Laprade's edited White Paper - Nilanjana Ray.docx

Table of Contents Executive summary ........................................................................................................................................ i Glossary ....................................................................................................................................................... iii 1 Introduction .......................................................................................................................................... 1 2 Is Java syntax slowing down development? .......................................................................................... 1 3 Market drivers ....................................................................................................................................... 1 3.1 Existing Java libraries .................................................................................................................... 2 3.2 Debugging in Java ......................................................................................................................... 2 4 Characteristics of an ideal Java-hosted language .................................................................................. 3 5 What is Clojure? .................................................................................................................................... 3 6 Where is Clojure used? ......................................................................................................................... 3 7 The power of Clojure ............................................................................................................................ 4 7.1 Syntax ........................................................................................................................................... 4 7.1.1 S-expressions ........................................................................................................................ 4 7.1.2 Polish/prefix notation ........................................................................................................... 4 7.2 Core functions and abstraction away from the type system ........................................................ 5 7.3 Java Interoperability ..................................................................................................................... 5 7.4 The REPL ....................................................................................................................................... 6 8 Conclusion ............................................................................................................................................ 7 9 Call to action ......................................................................................................................................... 7 References .................................................................................................................................................... 8 2

3.1 Existing Java libraries Java continues to be the top programming language in 2018, based on popular search engine hits from Google, Bing, Yahoo!, Wikipedia, Amazon, YouTube, and Baidu, but ratings (hits based on the mentioned search engines) seem to be decreasing every year [5]. In 2016, Java had a rating of 21.456% on TIOBE, but in 2018, its rating dropped to 15.932%, resulting in a drop of 5.524% in two years (See Figure 1 below). Figure 1: Screenshot of a popularity rating graph based on search engine hits related to the Java programming language throughout the years. Source: tiobe.com This means people are either losing interest in Java, or companies are beginning to move onto other programming languages instead. If companies that use Java move onto another language or platform, already-built software will have to be rewritten. This is not only ineffective cost-wise, but also time consuming and deteriorating development productivity. 3.2 Debugging in Java As mentioned by Xiabei Zhong [4], Java can be time-consuming to develop in. The developer must first write the code, compile it into Java bytecode, and then analyze errors and debug from there (Figure 2). When dealing with larger programs, compile times can increase, and if companies are in a rush to deliver software, this can be an issue when a development team is tight on time. 2

7.2 Core functions and abstraction away from the type system Clojure comes equipped with core functions designed to keep coding efficient. Many of these functions take from traditional LISP methods, where a main focus is on list iteration. Core functions, such as map , apply , and reduce , as examples, can all be applied to lists of elements without having to write any for loops, or declare any types. This keeps the developer focused on writing functional code, rather than focusing on getting the correct type. This also reduces the lines of code a developer must write, as a result, maintain. Code length is crucial when writing maintainable code. A comparison of how easy and efficient it is to write a simple function to find the average of a list of numbers can be seen below, with Java on the left, and Clojure on the right (see Figure 4 and Figure 5 below) [14]. Figure 4: a number averaging function in Java (Source: Clojure Programming [14]) Figure 5: a number averaging function in Clojure (Source: Clojure Programming [14]) 7.3 Java Interoperability Clojure is a hosted language on top of the JVM. This means that Clojure can use any function that was not only declared in Clojure, but also any Java function. This means it can work on top of already-existing Java code. It can call core Java libraries, external Java libraries, etc. This is possible, because Clojure is compiled to the same bytecode that Java is compiled to, Java bytecode. To represent Java code inside of Clojure, it uses a dot notation, where the existing Java function is prefixed with a period. Four examples of different interoperability methods can be seen in action below [15]: Instance method 1: (let [d (java.util.Date.)] (. D getTime)) 3

8 Conclusion Clojure, as a programming language, meets all of the ideal criteria for moving from one programming language to another, on the JVM, or, if needed, to another platform such as JavaScript/Node.js, or Microsoft’s .NET Common Language Runtime. It provides for a concise, consistent, and easy-to-read-and-write syntax, its REPL saves the developer time on debugging software, Java interoperability provides the developers the option to use existing Java libraries, and it includes efficient, time-saving core functions that will reduce the lines of code needed to write software. 9 Call to action For more info check out: ● https://clojure.org/ ● https://clojuredocs.org/ ● https://clojurescript.org/ ● http://lumo-cljs.org/ ● https://github.com/clojure/clojure-clr 6