BIA

:- dynamic(edge/3).
:- dynamic(node/1).

start :- write('\n1. Insert node'),
	write('\n2. Delete node'),
	write('\n3. Insert edge'),
	write('\n4. Delete edge'),
	write('\n5. Show graph'),
	write('\n6. Exit'),
	write('\nChoose option: '),
	read(X),
	start_program(X).

start_program(1) :- write('\nInput the name of the node: '), read(Node), assert(node(Node)), start.

start_program(2) :- write('\nInput the name of the node: '), read(Node), retractall(edge(Node, _, _)), retractall(edge(_, Node, _)), retract(node(Node)), start.

start_program(3) :- write('\nInput the first node: '),
	read(A),
	node(A),
	write('\nInput the second node: '),
	read(B),
	node(B),
	write('\nInput the cost: '),
	read(Cost),
	assert(edge(A, B, Cost)),
	start.

start_program(4) :- write('\nInput the name of the first node: '),
	read(A),
	write('\nInput the name of the second node: '),
	read(B),
	retractall(edge(A, B, _)),
	start.

start_program(5) :- display_graph(), start.

start_program(6).

display_graph() :- findall(X, node(X), NodeList), display_graph(NodeList).
display_graph([]) :- !, true.
display_graph([Item|Tail]):- findall(X, edge(Item, X, _), EdgeNodesList), display_edges(Item, EdgeNodesList), display_graph(Tail).
display_edges(_, []) :- true.
display_edges(Node, [Item|Tail]) :- edge(Node, Item, Cost), write('\n'), write(Node), write(' to '), write(Item), write(' with cost '), write(Cost), display_edges(Node, Tail).