Book Image

Perl 6 Deep Dive

By : Andrew Shitov
Book Image

Perl 6 Deep Dive

By: Andrew Shitov

Overview of this book

Perl is a family of high-level, general-purpose, interpreted, dynamic programming languages consisting of Perl 5 and Perl 6. Perl 6 helps developers write concise and declarative code that is easy to maintain. This book is an end-to-end guide that will help non-Perl developers get to grips with the language and use it to solve real-world problems. Beginning with a brief introduction to Perl 6, the first module in the book will teach you how to write and execute basic programs. The second module delves into language constructs, where you will learn about the built-in data types, variables, operators, modules, subroutines, and so on available in Perl 6. Here the book also delves deeply into data manipulation (for example, strings and text files) and you will learn how to create safe and correct Perl 6 modules. You will learn to create software in Perl by following the Object Oriented Paradigm. The final module explains in detail the incredible concurrency support provided by Perl 6. Here you will also learn about regexes, functional programming, and reactive programming in Perl 6. By the end of the book, with the help of a number of examples that you can follow and immediately run, modify, and use in practice, you will be fully conversant with the benefits of Perl 6.
Table of Contents (15 chapters)

Using actions

Grammars by themselves do not just parse the source text and extract data pieces from it. To make the program execute the code, actions are needed. Actions in grammars are pieces of Perl 6 code that are triggered when the grammar successfully parses a rule or a token.

Let us take a look at the variable-declaration rule:

rule variable-declaration {
'my' <variable>
}

When the grammar finds the sequence my $x in the source text, the rule is satisfied. At this point, you may add an action:

rule variable-declaration {
'my' <variable> {say 'Declaring a variable'}
}

An action can be a simple alert like this but it also may be much more complex code that will be executed as a reaction to the variable declaration.

To make the action act properly, it needs to know the type of the variable (whether it contains the $ or the @ sigil...