Resolve "complete mini project 2"

Closes #7 (closed)

project2/jobshop2.pl

+% Student exercise profile
+:- set_prolog_flag(occurs_check, error).        % disallow cyclic terms
+:- use_module(library(clpq)).
+
+jobshop3(Jobs, Schedule, Time) :- jobshop(3, 3, Jobs, Schedule, Time).
+
+jobshop(N, M, Jobs, Schedule, Time) :- 
+	% assert the given jobs have the expected size
+    length(Jobs, N),
+    Len is N*M, length(Schedule, Len),
+    maplist(inv_length(M), Jobs),
+    
+    % assert that the tasks are done in the right order
+    Len1 is N-1, 
+    numlist(0,Len1,L), 
+    maplist(order_tasks(N, M, Jobs, Schedule, Time), L),
+    
+ 	% TODO assert that jobs on machines do not overlap
+    
+    minimize(Time).
+
+inv_length(N, L) :- length(L, N).
+
+order_tasks(N, M, Jobs, Schedule, Time, J) :-
+    % First task is done after 0 unit of time.
+	Pos is J*N, 
+    nth0(Pos, Schedule, T0), {0 =< T0},
+    
+    % Every task begin after the previous one is done.
+    nth0(J, Jobs, Tasks),
+    Len is M-2, numlist(0,Len,L), 
+    maplist(order_tasks_(N, Tasks, Schedule, J), L),
+   	
+    % Last task finish before the total needed time.
+    Pos2 is J*N+M-1, 
+    nth0(Pos2, Schedule, TM),
+    Pos3 is M-1, 
+    nth0(Pos3, Tasks, (_,DM)),
+	{TM + DM =< Time}.
+    
+order_tasks_(N, Tasks, Schedule, J, T) :-
+	Pos is J*N+T, 
+    nth0(Pos, Schedule, T0),
+    Pos1 is J*N+T+1, 
+    nth0(Pos1, Schedule, T1),
+	nth0(T, Tasks, (_,D0)),
+	{T0+D0 =< T1}.
+
+%?- jobshop3([[(0,3), (1,2), (2,2)],
+%         [(0,2), (2,1), (1,4)],
+%         [(0,4), (1,4), (2,3)]],
+%         Shedule,
+%         Time).
+