Client view first

Abstract

When teaching certain CS topics (e.g., abstract data types, operating systems), the instructor tries to make clear the distinction between the "client" perspective and the "implementer" perspective. But when teaching some programming language features and related programming techniques, this dichotomy often is not respected as strongly as it should be. We illustrate this with a discussion of how to teach recursion, comparing a traditional approach with one that is careful not to blur the distinctions between client view and implementer view. The latter better supports new learners in the creation of a sound and consistent mental model for developing and reasoning about programs that involve recursion.