Why are not Perls patterns regular expressions?
Submitted by: AdministratorBecause Perl patterns have backreferences.
A regular expression by definition must be able to determine the next state in the finite automaton without requiring any extra memory to keep around previous state. A pattern /([ab]+)c1/ requires the state machine to remember old states, and thus disqualifies such patterns as being regular expressions in the classic sense of the term.
Submitted by: Administrator
A regular expression by definition must be able to determine the next state in the finite automaton without requiring any extra memory to keep around previous state. A pattern /([ab]+)c1/ requires the state machine to remember old states, and thus disqualifies such patterns as being regular expressions in the classic sense of the term.
Submitted by: Administrator
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