VisAST: Generic AST Visualiser for Software Language Education

Abstract

Structural concepts, like abstract syntax trees (ASTs), are often best explained through visual representations. Students seem to have little trouble understanding what is presented to them visually, but they find it harder to translate their visual conception into source code when programming assignments on their own. Few resources are available to help students make this connection between visual and textual representations. We developed a tool, visAST, for dynamically visualising ASTs of small languages written in Haskell, to help students connect the visual representations of ASTs to their own source code. The goal was to make the visualisations of visAST effortless to adopt for any new language that the students define. To assess the benefits and usability of visAST we conducted a user study, where visAST was used while implementing a simple interpreter. We asked students about their opinions on the tool and measured their performance with and without visAST. Our results show that students like visAST and find it useful. The results also suggest that visAST slightly improved students’ performance in a programming class.