Text-oriented structure commands for structure editors

The main problems associated with program structure editors are not inherent and can be solved without reverting to a textual viewpoint. Cursor movements can be made more natural by viewing the screen as a 2-D arrangement of nodes. Expressions can be input from left to right by rebinding operator keys to commands more complex than simple template expansion. Transformations of program fragments can be accomplished by an editor which supports matching and instantiation of subtrees.