Mixing Visual and Textual Code

Abstract: The dominant programming languages support nothing but linear text to express domain-specific geometric ideas. What is needed are hybrid languages that allow developers to create visual syntactic constructs so that they can express their ideas with a mix of textual and visual syntax tailored to an application domain. This mix must put the two kinds of syntax on equal footing and, just as importantly, the extended language must not disrupt a programmer's typical workflow. This means that any new visual syntax should be a proper language extension that is composable with other language features. Furthermore, the extensions should also preserve static reasoning about the program. This paper presents Hybrid ClojureScript the first such hybrid programming language. Hybrid ClojureScript allows programmers to add visual interactive syntax and to embed instances of this syntax within a program's text. An enhanced hybrid IDE can then display these embedded instances as mini-GUIs that programmers interact with, while other IDEs will show a textual representation of the syntax. The paper argues the necessity of such an extensibility mechanism, demonstrates the adoptability of the design, and discusses what might be needed to use the design in other languages.