Tcl_SaveResult,   Tcl_RestoreResult,  Tcl_DiscardResult  -
       save and restore an interpreter's result


       #include <tcl.h>

       Tcl_SaveResult(interp, statePtr)

       Tcl_RestoreResult(interp, statePtr)



       Tcl_Interp        *interp    (in)      Interpreter     for
                                              which  state should
                                              be saved.

       Tcl_SavedResult   *statePtr  (in)      Pointer to location
                                              where   interpreter
                                              result  should   be
                                              saved  or restored.


       These routines allows a C procedure to take a snapshot  of
       the  current interpreter result so that it can be restored
       after a call to Tcl_Eval or some other routine that  modi­
       fies  the interpreter result.  These routines are passed a
       pointer to a structure that is used to store enough infor­
       mation  to  restore  the  interpreter  result state.  This
       structure can be allocated on the  stack  of  the  calling
       procedure.   These  routines  do not save the state of any
       error information in the interpreter (e.g.  the  errorCode
       or errorInfo variables).

       Tcl_SaveResult  moves  the  string  and  object results of
       interp  into   the   location   specified   by   statePtr.
       Tcl_SaveResult clears the result for interp and leaves the
       result in its normal empty initialized state.

       Tcl_RestoreResult moves the string and object results from
       statePtr  back  into interp.  Any result or error that was
       already in the interpreter will be cleared.  The  statePtr
       is left in an uninitialized state and cannot be used until
       another call to Tcl_SaveResult.

       Tcl_DiscardResult releases  the  saved  interpreter  state
       stored  at  statePtr.   The  state structure is left in an
       uninitialized state and cannot be used until another  call
       result, either Tcl_RestoreResult or Tcl_DiscardResult must
       be  called to properly clean up the memory associated with
       the saved state.


       result, state, interp