Undo/redo technique for token-oriented representation of program code

A software engineering tool comprising:

• a representation of program code encoded in a computer readable medium as a doubly-linked list of nodes, each node corresponding to a respective token recognized in accordance with an operative set of lexical rules;
• functional encodings of edit methods, including at least insert-type and remove-type methods, the edit methods executable to operate on the list of nodes;
• and
• an undo-redo manager that maintains an ordered set of undo-redo objects in correspondence with operation of the edit methods, the undo-redo objects identifying opposing-end nodes of sublists of tokens inserted into the list and removed therefrom by operation of the insert-type and remove-type methods, respectively.

One or more computer readable media encoding a data structure that represents contents of an edit buffer as a sequence of lexical tokens, the encoded data structure comprising:

• a doubly linked list of nodes;
• token representations each corresponding to at least one respective node of the list, wherein at least some of the token representations have associated substring encodings;
• and
• an edit-operation-ordered representation of undo objects that each identify at least opposing end nodes of respective sublists of one or more lexical tokens that correspond to substrings that are either introduced into or removed from the list by edit operations.