Think Julia

Chapter 9. Case Study: Word Play

This chapter presents a second case study, which 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 Word Lists

For the exercises in this chapter we need a list of English words. There are lots of word lists available on the web, but the one most suitable for our purpose is one of the word lists collected and contributed to the public domain by Grady Ward as part of the Moby lexicon project. It is a list of 113,809 official crosswords; that is, words that are considered valid in crossword puzzles and other word games. In the Moby collection, the filename is 113809of.fic; you can download a copy, with the simpler name words.txt, from this book’s GitHub repository.

This file is in plain text, so you can open it with a text editor, but you can also read it from Julia. The built-in function open takes a name of the file as a parameter and returns a file stream you can use to read the file:

julia> fin = open("words.txt")
IOStream(<file words.txt>)

fin is a file stream used for input. When it is no longer needed, it has to be closed with close(fin).

Julia provides several function for reading, including readline, which reads characters from the file until it gets to a NEWLINE and returns the result ...