searchTree

Logic Programming in Prolog
•Search Trees
– voter
– farm buildings
•Remark
– I use _ to distinguish free variables: X, _X, __X, ___X etc.
– it may be easier to number: X, X, X, Xetc.
CSI2120: Programming Paradigms

Example from slides
name(joe).
name(jane).
citizen(jane).
citizen(joe).
adult(jane).
voter(X):-
name(X),
citizen(X),
adult(X).
?- voter(Y).
CSI2120: Programming Paradigms
voter(Y)
name(X), citizen(X),
adult(X)
citizen(joe), adult(joe)
adult(joe)
citizen(jane), adult(jane)
adult(jane)
Y=X
X=joe
X=jane

Example discussed on the board
Building categories:
parent(building,farmbuilding).
parent(farmbuilding,barn).
parent(farmbuilding,silo).
parent(farmbuilding,house).
parent(barn,horsebarn).
parent(barn,cowbarn).
typeof(X,Y):- parent(Z,X),typeof(Z,Y).
typeof(X,Y):- parent(Y,X).
?- typeof(cowbarn,A).
CSI2120: Programming Paradigms

CSI2120: Programming Paradigms
typeof(cowbarn, A)
parent(Z,cowbarn),typeof(Z,A)
typeof(barn,A)
parent(_Z,barn),typeof(_Z,A)
parent( A, cowbarn)
X=cowbarn, Y=A
Z=barn A=barn
_X=barn, _Y = A
typeof(farmbuilding,A)
parent(__Z,farmbuilding),typeof(__Z,A)
__X=farmbuidling, __Y = A
_Z=farmbuilding
__Z=building
typeof(building,A)
parent(___Z,building),typeof(___Z,A)
___X=building, __Y = A ____X=building, ___Y = A
parent(A, building)
A = building
parent(A, farmbuilding)
A = farmbuilding
parent( A, barn)
_____X=farmbuilding, ____Y = A
______X=barn, _____Y = A
_______X=cowbarn, ______Y = A