Explanation arrow: which rule justifies the atom?

[stephanzwicknagl]

• if component with multiple rules, it's not obvious which rule derived the atom
• highlight (bold?) rule when explanation is triggered
• the information is there, so it should be doable

[stephanzwicknagl]

example program

bend(X1,Y1,V) :- go(X,Y,X1,Y1,N,M); go(X1,Y1,_,_,N1,M1); N = N1; M = M1; bend(X,Y,V).
bend(X1,Y1,(V-1)) :- go(X,Y,X1,Y1,N,M); go(X1,Y1,_,_,N1,M1); N != N1; M != M1; bend(X,Y,V); (V-1) >= 0.
bend(X1,Y1,V) :- go(X,Y,X1,Y1,N,M);

Justifier program before

h(2, bend(X1,Y1,V), r) :- d, R1.
h(2, bend(X1,Y1,(V-1)), r) :- d, R2.
h(2, bend(X1,Y1,V), r) :- d, R3.

Justifier program edit

h(2, 1, bend(X1,Y1,V), r) :- d, R1.
h(2, 2, bend(X1,Y1,(V-1)), r) :- d, R2.
h(2, 3, bend(X1,Y1,V), r) :- d, R3.