Book Image

The Clojure Workshop

By : Joseph Fahey, Thomas Haratyk, Scott McCaughie, Yehonathan Sharvit, Konrad Szydlo
Book Image

The Clojure Workshop

By: Joseph Fahey, Thomas Haratyk, Scott McCaughie, Yehonathan Sharvit, Konrad Szydlo

Overview of this book

The Clojure Workshop is a step-by-step guide to Clojure and ClojureScript, designed to quickly get you up and running as a confident, knowledgeable developer. Because of the functional nature of the language, Clojure programming is quite different to what many developers will have experienced. As hosted languages, Clojure and ClojureScript can also be daunting for newcomers because of complexities in the tooling and the challenge of interacting with the host platforms. To help you overcome these barriers, this book adopts a practical approach. Every chapter is centered around building something. As you progress through the book, you will progressively develop the 'muscle memory' that will make you a productive Clojure programmer, and help you see the world through the concepts of functional programming. You will also gain familiarity with common idioms and patterns, as well as exposure to some of the most widely used libraries. Unlike many Clojure books, this Workshop will include significant coverage of both Clojure and ClojureScript. This makes it useful no matter your goal or preferred platform, and provides a fresh perspective on the hosted nature of the language. By the end of this book, you'll have the knowledge, skills and confidence to creatively tackle your own ambitious projects with Clojure and ClojureScript.
Table of Contents (17 chapters)
Free Chapter
2
2. Data Types and Immutability

2. Data Types and Immutability

Activity 2.01: Creating a Simple In-Memory Database

Solution:

  1. First, create the helper functions. You can get the Hash Map by executing the read-db function with no arguments, and write to the database by executing the write-db function with a Hash Map as an argument:
    user=>
    (def memory-db (atom {}))
    #'user/memory-db
    (defn read-db [] @memory-db)
    #'user/read-db
    user=> (defn write-db [new-db] (reset! memory-db new-db))
    #'user/write-db
  2. Start by creating the create-table function. This function should take one parameter: the table name. It should add a new key (the table name) at the root of our Hash Map database, and the value should be another Hash Map containing two entries – an empty vector at the data key and an empty Hash Map at the indexes key:
    user=>
    (defn create-table
      [table-name]
      (let [db (read-db)]
        (write-db (assoc db table-name {:data [] :indexes {}}))...