From: Venkatesan Guruswami (venkat@cs.washington.edu)
Date: Mon Apr 05 2004 - 11:52:32 PDT
Couple of things: 1. The Engineering library should have a copy of the textbook on reserve. They are dependent on someone returning it, but hopefully it will happen in the next 2-3 days. I asked about placing older editions on reserve, and there is a possibility of them getting hold of a 3rd edition from Bothell. 2. In class today there was the question on why "Not everyone in Seattle likes espresso" translates as " Exists x ( S(x) AND NOT(E(x) ) " instead of " Exists x ( S(x) implies NOT(E(x)) )" One way to see this is to just write it as negation of a universally quantified formula and use the negation laws/De Morgan's to simplify it, as we did in lecture. The implication statement becomes true as soon as there is someone who doesn't live in Seattle, regardless of whether there is someone who lives in Seattle that doesn't like espresso, and thus is an incorrect decription. Likewise, we can't say "Forall x (S(x) implies NOT(E(x))" since that captures the statement "Everyone in Seattle doesn't like espresso" which is not what was meant. If there is still some confusion, please raise this point in the TA sections. Venkat _______________________________________________ Cse321 mailing list Cse321@cs.washington.edu http://mailman.cs.washington.edu/mailman/listinfo/cse321
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