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Groovy for Domain-Specific Languages, Second Edition

Groovy for Domain-Specific Languages, Second Edition

By : Dearle
4.7 (3)
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Groovy for Domain-Specific Languages, Second Edition

Groovy for Domain-Specific Languages, Second Edition

4.7 (3)
By: Dearle

Overview of this book

The times when developing on the JVM meant you were a Java programmer have long passed. The JVM is now firmly established as a polyglot development environment with many projects opting for alternative development languages to Java such as Groovy, Scala, Clojure, and JRuby. In this pantheon of development languages, Groovy stands out for its excellent DSL enabling features which allows it to be manipulated to produce mini languages that are tailored to a project’s needs. A comprehensive tutorial on designing and developing mini Groovy based Domain Specific Languages, this book will guide you through the development of several mini DSLs that will help you gain all the skills needed to develop your own Groovy based DSLs with confidence and ease. Starting with the bare basics, this book will focus on how Groovy can be used to construct domain specific mini languages, and will go through the more complex meta-programming features of Groovy, including using the Abstract Syntax Tree (AST). Practical examples are used throughout this book to de-mystify these seemingly complex language features and to show how they can be used to create simple and elegant DSLs. Packed with examples, including several fully worked DSLs, this book will serve as a springboard for developing your own DSLs.
Table of Contents (14 chapters)
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1
1. Introduction to DSLs and Groovy
13
Index

Closures and collection methods


In the last chapter, we encountered Groovy lists and saw some of the iteration functions, such as the each method:

def flintstones = ["Fred","Barney"]

flintstones.each {
    println "Hello, ${it}"
}

This looks like it could be a specialized control loop similar to a while loop. In fact, it is a call to the each method of Object. The each method takes a closure as one of its parameters, and everything between the curly braces {} defines another anonymous closure.

Closures defined in this way can look quite similar to code blocks, but they are not the same. Code defined in a regular Java or Groovy style code block is executed as soon as it is encountered. With closures, the block of code defined in the curly braces is not executed until the call() method of the closure is made:

println "one"
def two = 
{ 
println "two" 
}
println "three"
two.call()
println "four"

This will print the following:

one
three
two
four

Let's dig a bit deeper into the structure of each...

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