Exploiting Logic Program Schemata to Teach Recursive Programming

Recursion is a complex concept that most novice logic programmers have difficulty grasping. Problems associated with recursion are avoided in imperative languages where iteration is provided as an alternative to recursion. Although difficult to learn, recursion is very easy to use once it is understood. In fact, many problems that have straightforward recursive solutions have very sophisticated iterative solutions. Many of the difficulties associated with learning recursion can be overcome by incorporating conditional recursion (i.e., a structured recursive equivalent to the WHILE loop) into logic programming languages. Two popular instructional techniques are collaborative learning and situated learning. The underlying claim of the situated cognition movement is the desire to enculturate the student into the domain of the teacher by involving the student in a series of authentic activities which are designed to incrementally improve the skills of the student. In the domain of computer programming, collaboration is an authentic activity. In this paper, we present logic program templates and schemata which add conditional recursion to logic programming languages and enable collaborative logic programming. Conditional recursion also provides a bridge to higher-order programming. Higher-order programming is the essence of abstraction in problem solving. Thus, in addition to aiding its students in acquiring the knowledge of recursion, conditional recursion also promotes abstract problem solving skills. We have successfully employed this schema-based approach to teaching recursion in several declarative programming languages with much success over the past four years.