Forth report: strap-on Forth

• Authors: Paul Frenger
• Venue: ACM SIGPLAN Notices
• Year: 2002

Human progress advances in many ways. One method obvious to all is to take something, a bicycle for instance, and make a multitude of small changes to the design over time. Each iteration of the refinement process gives us something newer and nicer to appreciate. That's how you start out with a $50 Schwinn bike and end up with a $10,000 Lotus racing bicycle.Another method is to add another layer of complexity onto the original design, some new technology never expected by the inventors of the product or device, to prevent natural obsolescence. An example here might be the internal combustion engine, invented in the pre-smog 1800's. Many layers of complexity have been applied to this product over the decades. Take fuel management for instance: we have gone from simple mechanical carburetion, to computerized electronic fuel injection, then added forced induction by supercharging / turbocharging. Each layer builds upon (and sometimes replaces) one or more older layers underneath itself.My homemade terminology for adding another layer of complexity or sophistication onto something where it wasn't found before is "strap-on technology". Where does the "strap-on" part come in? It's like in the movie, Six Days, Seven Nights by Touchstone Pictures, 1998 [1]. During an in-flight emergency, Harrison Ford crashes his tourist airplane on the beach of a small Pacific island, incidentally breaking the wheels of his landing gear in the process and stranding himself and Ann Heche there. He later finds two usable pontoons from a derelict 1940-era Japanese seaplane in the jungle. He uses vines and ropes to "strap-on" these pontoons over his broken wheels, thus enabling an essential water takeoff to escape from the tiny beach of that island. Ford "layered" the more advanced technology (pontoons for water takeoffs and landings) over the less advanced wheeled gear, in making his escape. The "strap-on" pontoons advance this movie's plot while, incidentally, illustrating my point about adding new technology to an older product.The remainder of this essay will give additional examples of "strap-on technology", finishing up with cases where the advanced layer which was applied involved the Forth programming language (hence the "strap-on Forth" terminology). As added zest for the reader, I will include some remarks on this subject by my friends at the comp.lang.forth newsgroup, who were invited to contribute examples or commentary of their own.