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)

Passing functions as arguments

Functions in Perl 6 can be passed to other functions as arguments. A typical example is a sort algorithm that needs a function to compare two values. Depending on the data types, it can be different functions that know how to compare the values of that type.

Let's examine the following tiny example:

sub less($a, $b) {$a < $b}
sub more($a, $b) {$a > $b}

sub compare($a, $b, $f) {
    $f($a, $b) 
}

say compare(10, 20, &less); # True
say compare(10, 20, &more); # False

The main code calls the compare sub with three arguments—two integer numbers and a reference to one of the functions—&less or &more. An ampersand before the name tells us that a function should not be called at this point (remember that, in Perl 6, parentheses are not required when calling a function).

Inside the compare function, the third argument...