Regex Set

Regular Expression

r

represents a pattern of string, where

\text{if } r=a, a \text{ in } \sum. \text{ } L(r) = \{a\}

\text{if } r=ɸ, \text{ } \text{ } L(r) = \{\} \text{ // empty set}

\text{if } r=ε, \text{ } L(r)=\{ε\} \text{ // a set with an empty string}