repetitions.Rmd

# Repetition Patterns {#repetion}

## Introduction

In this chapter, you will learn how to use _repetition metacharacters_ to gain more 
matching power in your regular expressions. We're going to start by looking at 
the three main metacharacters: the star---or asterisk--- `*`, the plus `+`, and 
the question mark `?`. Each one of these metacharacters has an effect on the token 
that immediately precedes it. That token could be a literal character, it could be 
a character set, or it could be a more complicated expression; a repetition 
metacharacter takes that preceding token and determines how many times that token 
can be repeated. In the case of the asterisk `*`, that token can be there 0 or 
more times; in the case of the plus `+`, it would be there one or more times; 
and with the question mark `?`, the token would just be there 0 time or one time.