next up previous contents index
Next: Debugging Up: Future Research Previous: Information Hiding   Contents   Index

Control Delimiters

We are currently developing a portable UNIX based Forth system written in C that is designed around a token threading scheme. It is designed to run Dreams efficiently even when cooperative multitasking Forth applications are being executed. This system is also designed to permit exploring several novel control constructs. Exception handling in ways similar to PL/1, Ada, Lisp and Scheme have caused us to consider an efficient way to implement these non-local exits in a Forth system [Bro90]. This opens the way to a complete Forth implementation of control delimiters [SF90]. These are very powerful concepts. It is amazing how hard it is to implement them in most languages (other than Lisp), but after developing the tree-structured stack concept, all of these control structures are almost obvious.


Robert J. Brown