Representing Program Edits with the Choice Calculus

Graduation date: 2015The problem of supporting more advanced selective undo operations has received a lot\ud of attention. However, selective undo is generally missing in commonly used editors.\ud Moreover, partial selective undo, the ability of undoing just part of some edit so that other\ud edits may be undone, is not supported at all. We observe that a fundamental obstacle is\ud the lack of a more flexible and compositional edit model. This project addresses this issue\ud and proposes the choice edit model, which is based on the representation provided by the\ud choice calculus. The central idea is to represent an edit through a choice that contains\ud the old and the new code as alternatives. Edits inherit properties from choices and can\ud thus be composed, nested, and transformed so that dependent edits may be untangled and\ud undone partially. The choice representation is an internal representation, not meant to\ud be exposed to programmers directly. To communicate the structure and dependencies of\ud edits we introduce program edit graphs as an alternative, more abstract representation.\ud Program edit graphs explicitly represent program variants and their relations. We also\ud discuss the scalability of PEGs