Regular Expression

Regular expression is a great tool to describe a computation structure Finite Automata.

basic rule

1st try

expression := term ('|' term) *

term := factor (factor) *

factor := element | element '*'

element := literal | '(' expression ')'

literal := one of printable except '(' ')' '|' '*' '\' | escape

escape := '\' '(' | '\' ')' | '\' '|' | '\' '\'

The problem of 1st try is that it does not address