Is (a|b)* the same as a|b?

Question

Is (a|b)* the same as a*|b*? In other words, does (a|b)* accept string which are combinations of as and bs?

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arshajii · Accepted Answer · 2014-07-15T18:02:00.057

11

Is (a|b)* the same as a*|b*?

They are not the same.

So, for example, ab will be matched by (a|b)* but not by a*|b*. Note also that anything matched by a*|b* will also be matched by (a|b)*.

edited Jul 15 '14 at 18:02

answered Jul 15 '14 at 17:50

arshajii

score 9 · Answer 2 · edited Jul 15 '14 at 17:54

9

No.

In case of (a|b)*, you can mix As and Bs (see demo).

In case of a*|b*, you can have either As or Bs (see demo).

edited Jul 15 '14 at 17:54

Amal Murali

answered Jul 15 '14 at 17:50

vittore

score 0 · Answer 3 · answered Nov 09 '21 at 16:39

0

a*|b* denotes {ε, "a", "b", "aa", "bb", "aaa", "bbb", ...}

(a|b)* denotes {ε, "a", "b", "aa", "ab", "ba", "bb", "aaa", aab, abb, aba, baa ...}

ε denote empty

answered Nov 09 '21 at 16:39

Szczerski

Is (a|b)* the same as a*|b*?