Maybe someone has already done this.  But the question in my mind is how much of Tcl can be implimented in Tcl itself.  Obviously you can't implement system calls in Tcl, but you could implement just about everthing else.  What commands/parts of Tcl would be in the minimal set?

   * Minimal set
   * "set" both scalar and array modes.
   * "eval" command
   * "unknown" 
   * "string index" command
   * "string length" command
   * "lindex" command
   * "list" command
   * what else???

* Things that could be simulated in Tcl (theoretically)

   1. interpreters (design?). 
   2. namespaces (design?). 
   3. expr (design?). 
   4. callstack (design?) .
   5. proc (design?) .
   6. if/while/switch/for/foreach.
   7. regexp (sounds hard) .
   8. package system (design?) .

   * What I expect to be hard
   1. expr
   2. regexp

   * What I don't expect to be done
   1. C API
   2. Things that need system calls 

   * Other languages are self hosting like this
   1. C => c compiler
   2. Python => PyPy
   3. Smalltalk 
   4. Others??

Of course I expect that this TclTcl would be very slow, but interesting, and very easy to port to embedded systems.