marius' stuff for the third tutorial session

Marius/uebung03/tips.pl

+%sometimes you may want to "tag" things onto a existing data structure
+
+% e.g. process(ListOfTriples) needs a list of triples
+%but you only have a list of pairs
+
+process(ListOfTriples):-
+	%does something
+	write(ListOfTriples).
+
+%now we need to merge .i.e tag on a dummy value 0 in our naive case here
+tag_on([(A,B)],[(A,B,0)]).
+tag_on([(A,B)|Tail],ListOfTriples):-
+	tag_on(Tail,TempListOfTriples),
+	ListOfTriples = [(A,B,0)|TempListOfTriples],!.
+
+tag_and_process(List):-
+	tag_on(List,NewList),
+	process(NewList).
+
+
+%Prolog offers multiple ways of sorting, this is one
+
+comp_triples(Delta, (C1,_,_),(C2,_,_)):-
+	compare(Delta,C1,C2).
+
+my_sort(ListOfTriples, SortedListOfTriples):-
+	predsort(comp_triples,ListOfTriples,SortedListOfTriples).
+
+%testcase
+test_my_sort(X):-
+	my_sort([(29,"E","E"),(13,"E","E"),(54,"E","E"),(9,"E","E")],X).
+
+%normal lists can bes sorted with sort(List,SortedList)
+
+
+%interface for your homework:
+
+% dfs(GoalValue, Tree, PathString, Cost)
+%
+% GoalValue is a String e.g. "G"
+% Tree is a tree e.g. tree("A",[(1,tree("B",[]))])
+% PathString shall contain the correct path from the beginning straight to the goal in the end
+% 	if you do not like strings, you may implement path as list
+% Cost is a number that shall contain the summed up cost in the end
+
+%Only the iterative deepening differs from that interface, as we have to give a Stepsize:
+% idfs(GoalValue,Tree,PathString,Cost,StepSize)
+
+% also please use write or any other form of writing to show the order in whch your code expands the nodes
+% that helps you and us to determine whether you code actually performs a BFS, DFS and so on
+
+
+% (and you could verify your answer to 3.1 with that technique)
+
+
+