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Tcl_GetIndexFromObj(3)                     Tcl Library Procedures                     Tcl_GetIndexFromObj(3)



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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.

       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 structure is given by offset.                     |

       int          off-                                                                                     |
       set       (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.
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DESCRIPTION
       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 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 nonmatching
       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 the first in a series of  string  ptrs  that |
       are spaced apart by offset bytes. This is particularly useful when processing things like Tk_Configu- |
       rationSpec, whose string keys are in the same place in each of several array elements.


SEE ALSO
       Tcl_WrongNumArgs


KEYWORDS
       index, object, table lookup



Tcl                                                  8.1                              Tcl_GetIndexFromObj(3)