More on Character Classes (Regex)
This lesson discusses the character classes of Regex in detail.
So far we have used character classes like [aeiou] (listing all allowed
characters literally), and [a-z] (specifying a range of characters).
There’s more to these.
One can negate classes by prepending a “not” character ^ inside the square
brackets. E.g. [^AEIOUaeiou] allows every character that is not a vowel.
So we can find all words that do not start with a vowel like so:
text = "A regular expression is a sequence of characters that define a search pattern."p text.scan(/\b[^AEIOUaeiou ][^ ]*\b/)
This means: Start at a word boundary, and allow everything that is not a vowel or a space as a first character, when it is optionally followed by one or many characters that are not a space, followed by a word boundary.
This will output:
["regular", "sequence", "characters", "that", "define", "search", "pattern"]
Also, regular expressions come with “baked-in”, predefined classes. For example ...
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