Think Perl 6

Chapter 8. Case Study: Word Play

This chapter is intended to let you practice and consolidate the knowledge you have acquired so far, rather than introducing new concepts. To help you gain experience with programming, we will cover a case study that involves solving word puzzles by searching for words that have certain properties. For example, we’ll find the longest palindromes in English and search for words whose letters appear in alphabetical order. And I will present another program development plan: reduction to a previously solved problem.

Reading from and Writing to Files

For the exercises in this chapter, we will need our programs to read text from files. In many programming languages, this often means that we need a statement to open a file, then a statement or group of statements to read the file’s content, and finally a statement to close the file (although this last operation may be performed automatically in some circumstances).

We are interested here in text files that are usually made of lines separated by logical newline characters; depending on your operating system, such logical newline characters consist of either one (Linux, Mac) or two (Windows) physical characters (bytes).

The Perl built-in function open takes the path and name of the file as a parameter and returns a file handle (IO::Handle object) which you can use to read the file (or to write to it):

my $fh = open("path/to/myfile.txt", :r);
my $data = $fh.slurp-rest;
$fh.close;

The :r option is the file mode ...