What was new in this chapter?
Exponentiation in Ruby
nil when a method’s operation is not possible
More recursion and exit conditions
Modules and Inheritance
Array.detect (“find first”)
Exiting the entire script with
Parsing XML files with regular expressions
Writing to YAML files with
Reading from YAML files with
It’s almost as if this chapter weren’t really about numbers—we covered a large amount of generically useful information, especially Modules, Class Variables, and external data storage and retrieval using either XML or YAML (or both). We’ve done a bit of functional programming already in the last two chapters, but ...