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Add practical no. 1 and 2 from chapter 3.

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Kyle Isom 2018-01-17 13:16:17 -08:00
parent 5dd0bfcf19
commit 311a24961c
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60
lpn/ch03/connected.pl Normal file
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@ -0,0 +1,60 @@
%% Imagine that the following knowledge base describes a maze. The
%% facts determine which points are connected, that is, from which
%% points you can get to which other points in one step. Furthermore,
%% imagine that all paths are one-way streets, so that you can only
%% walk them in one direction. So, you can get from point 1 to point
%% 2, but not the other way round.
connected(1,2).
connected(3,4).
connected(5,6).
connected(7,8).
connected(9,10).
connected(12,13).
connected(13,14).
connected(15,16).
connected(17,18).
connected(19,20).
connected(4,1).
connected(6,3).
connected(4,7).
connected(6,11).
connected(14,9).
connected(11,15).
connected(16,12).
connected(14,17).
connected(16,19).
%% Write a predicate path/2 that tells you from which points in the
%% maze you can get to which other points when chaining together
%% connections given in the above knowledge base. Can you get from
%% point 5 to point 10? Which other point can you get to when starting
%% at point 1? And which points can be reached from point 13?
path(X, Y) :- connected(X, Y).
path(X, Y) :- connected(X, Z),
path(Z, Y).
%% Questions:
%% 1. Can you get from point 5 to point 10? Yes:
%%
%% ?- path(5, 10).
%% true .
%%
%% 2. Which other point can you get when starting at point 1? You can't
%% get to any other points:
%%
%% ?- path(1, P).
%% P = 2 ;
%% false.
%%
%% 3. Which points can be reached from point 13? Points 9, 10, 14, 17,
%% 18.
%%
%% ?- path(13, P).
%% P = 14 ;
%% P = 9 ;
%% P = 17 ;
%% P = 10 ;
%% P = 18 ;
%% false.

46
lpn/ch03/travel.pl
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@ -11,3 +11,49 @@ directTrain(nancy,metz).
travelFromTo(X, Y) :- directTrain(X, Y). travelFromTo(X, Y) :- directTrain(X, Y).
travelFromTo(X, Y) :- directTrain(X, Z), travelFromTo(X, Y) :- directTrain(X, Z),
travelFromTo(Z, Y). travelFromTo(Z, Y).
%% New version from practical exercises.
%% We are given the following knowledge base of travel information:
byCar(auckland,hamilton).
byCar(hamilton,raglan).
byCar(valmont,saarbruecken).
byCar(valmont,metz).
byTrain(metz,frankfurt).
byTrain(saarbruecken,frankfurt).
byTrain(metz,paris).
byTrain(saarbruecken,paris).
byPlane(frankfurt,bangkok).
byPlane(frankfurt,singapore).
byPlane(paris,losAngeles).
byPlane(bangkok,auckland).
byPlane(singapore,auckland).
byPlane(losAngeles,auckland).
%% Write a predicate travel/2 which determines whether it is possible
%% to travel from one place to another by chaining together car,
%% train, and plane journeys. For example, your program should answer
%% yes to the query travel(valmont,raglan).
%% The base case is a direct route via car, train or plane.
travelDirect(X, Y) :- byCar(X, Y).
travelDirect(X, Y) :- byTrain(X, Y).
travelDirect(X, Y) :- byPlane(X, Y).
travel(X, Y) :- travelDirect(X, Y).
%% The recursive case chains these together.
travel(X, Y) :- travel(X, Z),
travel(Z, Y).
%% So, by using travel/2 to query the above database, you can find out
%% that it is possible to go from Valmont to Raglan. If you are
%% planning such a voyage, that’s already something useful to know,
%% but you would probably prefer to have the precise route from
%% Valmont to Raglan. Write a predicate travel/3 which tells you which
%% route to take when travelling from one place to another. For
%% example, the program should respond
%% X = go(valmont,metz,
%% go(metz,paris,
%% go(paris,losAngeles)))
%% to the query travel(valmont,losAngeles,X).