----------------------------------------------------------- New Message on BDOTNET
----------------------------------------------------------- From: spark Message 4 in Discussion Considering that there maynot be many more replies forthcoming, let me venture to say something. In computer science there is a classical distinction made between a language recogniser/acceptor and a language generator. A regular expression is a language acceptor. Give an expression it will accept any string that matches the pattern that you have specified. This pattern can be thought of as the input language that is expressed by the regular expression. The same way we are trained to accept english or the way csc is built to accept a c# langauge pattern. Now a regex is internally mapped into a state machine. A state machine represents a set of states and trasnistions between states. These transitions maybe through the accepting of an inout or a null transition, one that occurs without any accepting any input. For example, condier the regex "abc" The state machine would look like this (s0) -a-> (s1) -b-> (s2)-c->(sF) where sF is the final state. Only is the correct input symbols are avilable at each state, will teh correct transitions occur. A state machine for "a(b|c)" will look like (s0) -a-> (s1) --b-->(sF) (s1)--c-->(SF) which has two out going paths from state s1. A generator for a regex, I would expect would have to generate the state machine and apply sequqnces that make atleast one path from s0 to sF to succeed at all times. This is probably easy to do when the language described by your state machine accepts only a finite set of words (like is this case accepts only ab and ac). But in cases where it accepts an infinite number of words, it might be hard to produce any meaningful output (like a(b|c)*). regards Roshan James ----------------------------------------------------------- To stop getting this e-mail, or change how often it arrives, go to your E-mail Settings. http://groups.msn.com/bdotnet/_emailsettings.msnw Need help? If you've forgotten your password, please go to Passport Member Services. http://groups.msn.com/_passportredir.msnw?ppmprop=help For other questions or feedback, go to our Contact Us page. http://groups.msn.com/contact If you do not want to receive future e-mail from this MSN group, or if you received this message by mistake, please click the "Remove" link below. On the pre-addressed e-mail message that opens, simply click "Send". Your e-mail address will be deleted from this group's mailing list. mailto:[EMAIL PROTECTED]
