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Tcl_GetIndexFromObj(3)		      Tcl Library Procedures		   Tcl_GetIndexFromObj(3)

_________________________________________________________________________________________________

NAME
       Tcl_GetIndexFromObj, Tcl_GetIndexFromObjStruct - lookup string in table of keywords

SYNOPSIS
       #include <tcl.h>

       int
       Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,
       indexPtr)

       int
       Tcl_GetIndexFromObjStruct(interp, objPtr, structTablePtr, offset,
				 msg, flags, indexPtr)

ARGUMENTS
       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 internal representation is
						modified to hold the index of the matching  table
						entry.

       const char **tablePtr (in)		An  array of null-terminated strings.  The end of
						the array is marked by	a  NULL  string  pointer.
						Note  that  references	to  the  tablePtr  may be
						retained  in  the  internal   representation   of
						objPtr, so this should represent the address of a
						statically-allocated array.

       const void *structTablePtr (in)		An array of arbitrary type, typically some struct
						type.	The first member of the structure must be
						a null-terminated string.  The size of the struc-
						ture is given by offset.  Note that references to
						the structTablePtr may be retained in the  inter-
						nal representation of objPtr, so this should rep-
						resent	the  address  of  a  statically-allocated
						array of structures.

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

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

       int flags (in)				OR-ed  combination  of	bits providing additional
						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 here.
_________________________________________________________________

DESCRIPTION
       These procedures provide 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.	Tcl_GetIndexFromObj compares objPtr 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 non-empty 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 match-
       ing 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 is not NULL.  Msg is included in the error message to indicate
       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_GetIndexFromObj will treat it as a non-matching value and return
       TCL_ERROR.

       Tcl_GetIndexFromObjStruct works just like  Tcl_GetIndexFromObj,	except	that  instead  of
       treating  tablePtr  as an array of string pointers, it treats it as a pointer to the first
       string in a series of strings that have offset bytes between them (i.e. that  there  is	a
       pointer	to  the  first	array of characters at tablePtr, a pointer to the second array of
       characters at tablePtr+offset bytes, etc.)  This is particularly  useful  when  processing
       things  like Tk_ConfigurationSpec, whose string keys are in the same place in each of sev-
       eral array elements.

SEE ALSO
       Tcl_WrongNumArgs

KEYWORDS
       index, object, table lookup

Tcl					       8.1			   Tcl_GetIndexFromObj(3)
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