Re: Regular Expressions and ^*
- From: Jamal Mazrui <empower@xxxxxxxxx>
- To: programmingblind@xxxxxxxxxxxxx
- Date: Sun, 14 Mar 2010 11:26:32 -0400
Hi Jared,
I'm not familiar with the use of the ^ you mention. As far as I know,
that example is not a valid regular expression. The only two uses of ^
to my knowledge are to denote the start of the source string and to
negate a character class inside square brackets.
Jamal
On 3/8/2010 6:55 PM, Jared Wright wrote:
I am familiar with ^ in regular expressions negating a character class
as well as requiring that a match must come at the start of the line.
But I am having trouble discerning what ^* in certain contexts is
supposed to indicate. I know that the expression (1^*(01^*01^*)^*) \cup
(0^*(10^*10^*)^*) matches all strings in a binary alphabet with an even
number of 0's or 1's, but I guess I'm having trouble talking myself from
the regular expression to an informal description of what it's matching.
Similarly, I'm having trouble deducing what would match the expression
(a|b)^*ba(ab*|ba*) particularly as relates to (a|b)^*
Any guidance welcome.
Jared
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