Description
For the five problems in this assignment, we define a relation enroll(Stu, Courses)and a
relation teach(Prof, Courses). In enroll(Stu, Courses), Stu is a student ID, and
Courses is a list of course IDs the student Stu enrolls in. In teach(Prof, Courses), Prof
is a professor id, and Courses is a list of course IDs taught by professor Prof. The course IDs in
each enroll fact and each course fact are distinct.
Assume all input data are correct.
Examples are based on the following database:
/* The database of enroll and teach facts */
enroll(1701, [c01, c10]).
enroll(1602, [c21]).
enroll(1711, [c01, c21, c10]).
enroll(1501, []).
teach(p01, [c01, c21]).
teach(p02, [c23]).
teach(p03, [c10]).
teach(p04, []).
1. Listing all the professors of a student’s enrollments
Define a relation prof_ids(Stu, L) that specifies a list L of all the professor IDs of a student’s
enrollment. The order of professor IDs in L corresponds to the order of courses taught by these
professors in enroll(Stu, Courses).
Examples:
?- prof_ids(1701, L).
L = [p01, p03].
?- prof_ids(1501, L).
L = [].
?- prof_ids(Stu, [p01]).
Stu = 1602 ;
false.
?- prof_ids(Stu, [p01, p02]).
false.
?- prof_ids(Stu, [p01, p03]).
Stu = 1701 ;
false.
?- prof_ids(Stu, [p01, p03, p04]).
false.
?- prof_ids(Stu, L).
Stu = 1701,
L = [p01, p03] ;
Stu = 1602,
L = [p01] ;
Stu = 1711,
L = [p01, p01, p03] ;
Stu = 1501,
L = [].
2. Listing common enrollments of two students
Write a relation common_enroll (X, Y, L) that specifies a list L of courses that two different
students X and Y both enroll in.
Examples:
?- common_enroll(1701, 1602, L).
L = [].
?- common_enroll(1701, 1501, L).
L = [].
?- common_enroll(1701, 1711, L).
L = [c01, c10].
?- common_enroll(1701, 1711, []).
true.
?- common_enroll(1701, 1711, [c01]).
true.
?- common_enroll(1701, 1711, [c01, c23]).
false.
?- common_enroll(1701, 1711, [c10, c01]).
true.
?- common_enroll(1701, Y, L).
Y = 1602,
L = [] ;
Y = 1711,
L = [c01, c10] ;
Y = 1501,
L = [] ;
false.
?- common_enroll(X, 1711, L).
X = 1701,
L = [c01, c10] ;
X = 1602,
L = [c21] ;
X = 1501,
L = [] ;
false.
3. Listing distinct students that enroll in a professor’s course(s)
Write a relation student_list(Prof, L) that specifies a list L of distinct students that enroll
in at least one course taught by the professor Prof.
Examples:
?- student_list(p01, L).
L = [1711, 1602, 1701].
?- student_list(p02, L).
L = [].
?- student_list(p04, L).
L = [].
?- student_list(p01, []).
true.
?- student_list(p01, [1701, 1711]).
true.
?- student_list(p01, [1501, 1711]).
false.
?- student_list(X, L).
X = p01,
L = [1711, 1602, 1701] ;
X = p02,
L = [] ;
X = p03,
L = [1711, 1701] ;
X = p04,
L = [].
4. Listing courses taught by the professors
Write a relation course_list(L) that specifies a list L of courses taught by the professors in the
teach facts.
Examples:
?- course_list(L).
L = [c01, c21, c23, c10].
?- course_list([]).
true.
?- course_list([c01]).
true.
?- course_list([c23, c21]).
true.
?- course_list([c23, c02]).
false.
?- course_list([c01, c21, c23, c10]).
true.
5. Counting the number of students that enroll in a course
Write a relation count_students(C, N) that counts the number of students that enroll in the
course C.
Examples:
?- count_students(c01, N).
N = 2.
?- count_students(c01, 2).
true.
?- count_students(c01, 0).
false.
?- count_students(c23, N).
N = 0.
?- count_students(c10, N).
N = 2.
?- count_students(X, 2).
X = c01 ;
X = c21 ;
X = c10.
?- count_students(X, 0).
X = c23 ;
false.
?- count_students(X, 1).
false.
?- count_students(X, N).
X = c01,
N = 2 ;
X = c21,
N = 2 ;
X = c23,
N = 0 ;
X = c10,
N = 2.
