Continuations in Tcl, an attempt to implement it

[jacque...@googlemail.com]

Continuation is a powerful language feature, that can help to solve in
simple and elegant ways some kind of programming task...
Tcl doesn't provide it yet, nor is it's current implementation
"adapted" for an easy "addition" of it....

Several years ago, I implemented some sort of continuation in the Tcl
7.3 version. Some months later I found in the Internet an other
implementation of continuations in a Tcl Interp called AgentTcl; I
didn't try to understand how it was done, my impl. worked for me.

Some years later, I had a look at the Tcl 8.x versions and discovered
the switch from "pure strings" to the "Tcl_Obj" and also the
"byte-compiler"; this didn't inspire me much to "reimplement
continuations"....

This summer, I made a "real try", first beginning with a "pure tcl"
way-of-doing, based on "code intrumentation" (but soon I realized that
this wouldn't be satifying for a "strong" and "truly useable" feature),
followed by attempt to do it as a Tcl Extension. This was better
looking from the "application side" (tcl scripting), but "too bad"
regarding the C code (too much dupplication of Tcl core code, no chance
to be maintained...). Finally I came up with an impl. as Extension
requiring some changes in the Tcl C core......

Further readings and some code to experiment with is available at my
web home page: http://jacqkl.perso.chez-alice.fr/