I don't think that ' if not ((a in X) or (b in X)) then...' is correct. Basically the if statement will fail if there is anything in the X other than A or B.
Ie X = [] or [a] or [b] or [a,b] will succeed X = [c] or [a, c] etc will fail I would suggest If (X = []) or (X = [a]) or (x = [b]) or (X = [a,b]) then... But the original code seems fine to me. Regards Sean Cross IT Systems Development Manager Catalyst Risk Management PO Box 230 50 Dalton St Napier 4140 DDI: 06-8340362 mobile: 021 270 3466 Visit us at http://www.catalystrisk.co.nz/ Offices in Auckland, Napier, Wellington & Christchurch Disclaimer: "The information contained in this document is confidential to the addressee(s) and may be legally privileged. Any view or opinions expressed are those of the author and may not be those of Catalyst Risk Management. No guarantee or representation is made that this communication is free of errors, viruses or interference. If you have received this e-mail message in error please delete it and notify me. Thank you." > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:delphi-talk- > [EMAIL PROTECTED] On Behalf Of Dan Kloke > Sent: Wednesday, 18 April 2007 12:21 p.m. > To: Delphi-Talk Discussion List > Subject: Re: Question on Set operator > > the original code can be read as: > > "if removing both a and b from X leaves the empty set, then..." > > or could be recoded as: > > if not ((a in X) or (b in X)) then... > > [EMAIL PROTECTED] wrote: > > Hi All, > > > > I've inherited some code that I need to integrate into some existing > > code. The author of the old code is using a construct I don't > > understand. There are things like: > > > > if (X - [a, b]) = [] then ... > > > > where "X" is a set and "a" and "b" are valid members of that set. My > > understanding of sets is that this should be the same as: > > > > if (a in X) or (b in X) then... > > > > but it isn't, because if I replace the first "if" with the second, > > the program behavior changes. > > > > Can someone help me with my conceptual gap and explain what the first > > "if" is saying? Thanks. > > > > > > Regards, > > Sid Gudes > > PIA Systems Corporation > > [EMAIL PROTECTED] > > > > > > __________________________________________________ > > Delphi-Talk mailing list -> Delphi-Talk@elists.org > > http://www.elists.org/mailman/listinfo/delphi-talk > __________________________________________________ > Delphi-Talk mailing list -> Delphi-Talk@elists.org > http://www.elists.org/mailman/listinfo/delphi-talk __________________________________________________ Delphi-Talk mailing list -> Delphi-Talk@elists.org http://www.elists.org/mailman/listinfo/delphi-talk
