... ... @@ -104,9 +104,42 @@ the length of a list is non-negative. We now consider another, slightly more complex example: to use \why\ to solve a little puzzle known as Einstein's logic problem''\footnote{This was contributed by St\'ephane Lescuyer.}. The problem is stated as follows. The problem is stated as follows. Five persons, of five different nationalities, live in five houses in a row, all painted with different colors. These five persones own different pets, drink different beverages and smoke different brands of cigars. We are given the following information: \begin{itemize} \item TODO \item The Englishman lives in a red house; \item The Swede has dogs; \item The Dane drinks tea; \item The green house is on the left of the white one; \item The green house's owner drinks coffee; \item The person who smokes Pall Mall has birds; \item The yellow house's owner smokes Dunhill; \item In the house in the center lives someone who drinks milk; \item The Norwegian lives in the first house; \item The man who smokes Blends lives next to the one who has cats; \item The man who owns a horse lives next to the one who smokes Dunhills; \item The man who smokes Blue Masters drinks beer; \item The German smokes Prince; \item The Norwegian lives next to the blue house; \item The man who smokes Blends has a neighbour who drinks water. \end{itemize} The question is: what is the nationality of the fish's owner? ... ... @@ -206,9 +239,17 @@ this theory. neighbour (Owner.to (Cigar.to Blend)) (Owner.to (Drink.to Water)) end \end{verbatim} Finally, we declare the goal in a fourth theory \begin{verbatim} theory Problem "Goal of Einstein's problem" use import Einstein use import EinsteinHints TODO goal G: Pet.to Fish = German end \end{verbatim} and we are ready to use \why\ to discharge this goal with any prover of our choice. %%% Local Variables: %%% mode: latex ... ...