On the interplay between bottom-up and datatype-driven program design

Abstract

When students are faced with a programming problem unlike any they have solved before, prior research suggests that they develop code backwards from essential computations in the problem. Some curricula, however, teach students to first write scaffolding code based on the type of the input data. How do these two approaches interact? We gave CS1 students who were taught to write scaffolding code a programming problem unlike any they had seen before. We found that while students put essential computations into the scaffolds, they often overuse affordances of the scaffolds in ways that lead to plan-composition errors. We propose that steering students away from on-the-fly decomposition while programming could help avoid some of these errors.