Tcl_GetIndexFromObj,  Tcl_GetIndexFromObjStruct  -  lookup
       string in table of keywords


       #include <tcl.h>

       Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,

       int                                                        |
       Tcl_GetIndexFromObjStruct(interp, objPtr, tablePtr, offset,|
       msg, flags, indexPtr)                                      |


       Tcl_Interp   *interp      (in)      Interpreter to use for
                                           error   reporting;  if
                                           NULL, then no  message
                                           is provided on errors.

       Tcl_Obj      *objPtr      (in/out)  The  string  value  of
                                           this object is used to
                                           search         through
                                           tablePtr.   The inter­
                                           nal representation  is
                                           modified  to  hold the
                                           index of the  matching
                                           table entry.

       char         **tablePtr   (in)      An  array of null-ter­
                                           minated strings.   The
                                           end  of  the  array is
                                           marked   by   a   NULL
                                           string pointer.        |

       int          offset       (in)                                    ||
                                           The offset to  add  to |
                                           tablePtr to get to the |
                                           next  string  in   the |
                                           list.  The  end of the |
                                           array is marked  by  a |
                                           NULL string pointer.

       char         *msg         (in)      Null-terminated string
                                           describing   what   is
                                           being  looked up, such
                                           as    option.     This
                                           string  is included in
                                           error messages.

                                           tional information for
                                           operation.   The  only
                                           bit that is  currently
                                           defined  is TCL_EXACT.

       int          *indexPtr    (out)     The   index   of   the
                                           string   in   tablePtr
                                           that matches the value
                                           of  objPtr is returned


       This procedure provides an efficient way  for  looking  up
       keywords,  switch  names, option names, and similar things
       where the value of an object must be one of  a  predefined
       set  of  values.   ObjPtr  is compared against each of the
       strings in tablePtr to find a match.  A  match  occurs  if
       objPtr's  string  value is identical to one of the strings
       in tablePtr, or if it is a unique abbreviation for exactly
       one  of the strings in tablePtr and the TCL_EXACT flag was
       not specified; in either case the index  of  the  matching
       entry is stored at *indexPtr and TCL_OK is returned.

       If  there  is no matching entry, TCL_ERROR is returned and
       an error message is left  in  interp's  result  if  interp
       isn't NULL.  Msg is included in the error message to indi­
       cate what was being looked up.  For  example,  if  msg  is
       option  the error message will have a form like bad option
       "firt": must be first, second, or third.

       If Tcl_GetIndexFromObj completes successfully it  modifies
       the  internal representation of objPtr to hold the address
       of the table and the index  of  the  matching  entry.   If
       Tcl_GetIndexFromObj  is invoked again with the same objPtr
       and tablePtr arguments (e.g. during a  reinvocation  of  a
       Tcl  command),  it  returns the matching index immediately
       without  having  to  redo  the  lookup  operation.   Note:
       Tcl_GetIndexFromObj  assumes  that the entries in tablePtr
       are static: they must not change between invocations.   If
       the  value of objPtr is the empty string, Tcl_GetIndexFro­
       mObj will treat it as  a  non-matching  value  and  return
       TCL_ERROR.                                                 |

       Tcl_GetIndexFromObjStruct works just like Tcl_GetIndexFro­ |
       mObj, except that instead of treating tablePtr as an array |
       of  string pointers, it treats it as the first in a series |
       of string ptrs that are spaced apart by offset bytes. This |
       is particularly useful when processing things like Tk_Con­ |
       figurationSpec, whose string keys are in the same place in |
       each of several array elements.


       index, object, table lookup