CODEWITHSUNDEEP
prolog
TL7
TL7

Reputation: 1

Prolog geometric triangle rules

Any examples on how to create rules in prolog for equilateral and isosceles triangle in 2d point?

Start with these: 

equilateral(point2d(x,y), point2d(x,y), point2d(x,y))
isosceles(point2d(x,y), point2d(x,y), point2d(x,y))

Upvotes: 0

Views: 346

Answers (1)

damianodamiano
damianodamiano

Reputation: 2662

To check if the triangle is equilateral, it's quite simple. To check if it is isosceles, it's a little less trivial. Here my solution:

seg_length(X1,Y1,X2,Y2,D):-
    D is sqrt(((X2-X1)**2)+((Y2-Y1)**2)).

equilateral(point2d(X1,Y1), point2d(X2,Y2), point2d(X3,Y3)):-
    seg_length(X1,Y1,X2,Y2,D),
    seg_length(X2,Y2,X3,Y3,D),
    seg_length(X3,Y3,X1,Y1,D).

isosceles(point2d(X1,Y1), point2d(X2,Y2), point2d(X3,Y3)):-
    seg_length(X1,Y1,X2,Y2,D1),
    seg_length(X2,Y2,X3,Y3,D2),
    seg_length(X3,Y3,X1,Y1,D3),
    L = [D1,D2,D3],
    sort(L,LS),
    length(L,LenL),
    length(LS,LenLS),
    LenL \== LenLS.

To check if at least two sides are equal, i use sort/2 which removes duplicates from the list. If the two lists have the same lenght, it means that all three sides are different and so the triangle is not isosceles.

Upvotes: 1

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