Regular Expressions Flashcards

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Regular Expressions

The basics of regular expression syntax and a few examples.

What is the syntax for a choice between $R_{1}$ and $R_{2}$ ?

$R_{1} ∣ R_{2}$

What is the syntax for a character?

$c$ (where c is any character)

What is the syntax for a concatenation of $R_{1}$ and $R_{2}$ ?

$R_{1} R_{2}$

What is the syntax for the Kleene star of $R$ ?

$R^{*}$

What is the Kleene star operation?

It represents zero or more occurrences of the preceding element.

How is the empty string represented?

By the symbol $ϵ$

What does the regular expression $a ∣ b$ match?

Either the character 'a' or the character 'b'

What does the regular expression $ab$ match?

The string ab

What does the regular expression $a^{*}$ match?

Any string of zero or more 'a' characters (including the empty string)

What does the regular expression $(a ∣ b)^{*}$ match?

Any string composed of 'a' and 'b' characters in any order, including the empty string

Import this source into your Adalyn library to start learning with spaced repetition.