compilation - Regular Expression Format Confusion -


i'm trying head around regular expression later program compiler.

if have expression:

(a or b)*

is same a* or b*? or mean can choose or b 0 or more times.

for example, using regular expression, can generate {ababababa} or strings of {aaaaaaa} or {bbbbbbb}? if input symbol b mean b can occur 0 or more times or can occur second time too?

thanks much

in regex libraries, or operator spelled |, regex (a|b)*.

that indeed means "any string of length (including 0) made of as , bs". in other words, parentheses work in algebraic expression, define subexpression: * (postfix) operator applied subexpression a|b.

interesting fact: (a*b*)* same set of strings (a|b)*.


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