Position: Meeting the Promise of Blocks-as-AST-Nodes Editing with “Typeblocking”

Despite the benefits [1, 2, 3] of “thinking in blocks” and using AST nodes as the unit of editing of programs [4], most blocks-based editors today remain clunky and slow because of a reliance on drag and drop, leading to a widely-held perception that text is a more efficient means of constructing a program [5]. However, there is no inherent property of blocks that limits them to being assembled in this manner. Indeed, by enabling keyboard-based editing of blocks, we posit that we should be able to match or surpass the efficiency of text while retaining the benefits of an AST-based program abstraction.Beginning with Corey McCaffrey's master's thesis in 2006 [6], and continuing with Terrance Liang's master's thesis in 2019 [7], the StarLogo Nova team is investigating ways to make blocks-based editing as efficient and intuitive as it should be, while keeping the abstractions firmly situated at the level of blocks/AST nodes rather than relying on textual representations. This position paper presents the design of StarLogo Nova's Typeblocking system, including a discussion of related tools whose designs heavily influenced StarLogo Nova, and initial findings about the efficiency of Typeblocking.