Remarkable is the fully interactive way of working in the REPL (Lisp's Read Eval Print Loop) and through the GUI, including live editing all classes/etc. via menus. LOOPS extended Interlisp with various ways to do object-oriented programming and a rule-system.
There is also a "friendly primer" for Xerox LOOPS, from mid 1980s. https://bitsavers.org/pdf/xerox/interlisp-d/198510_Koto/3102...
Note that LOOPS is an early OOP System, it's not a about iteration in a loop.