see for example a structure editor for Lisp, ca. 1967, described by L Peter Deutsch: https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=028a167a1c7

see for example a structure editor for Lisp, ca. 1967, described by L Peter Deutsch: https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=028a167a1c72aa817d9d5b8aa6e9099a75bd454f https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&d...