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TAG_EXIST

TAG_EXIST

Name


      TAG_EXIST()

Purpose


      To test whether a tag name exists in a structure.

Explanation


      Routine obtains a list of tagnames and tests whether the requested one
      exists or not. The search is recursive so if any tag names in the
      structure are themselves structures the search drops down to that level.
      (However, see the keyword TOP_LEVEL).
             

Calling Sequence


      status = TAG_EXIST(str, tag, [ INDEX =, /TOP_LEVEL, /QUIET ] )
   

Input Parameters


      str - structure variable to search
      tag - tag name to search for, scalar string

Outputs


      Function returns 1b if tag name exists or 0b if it does not.
                             

Optional Input Keyword


      /TOP_LEVEL = If set, then only the top level of the structure is
                          searched.
      /QUIET - if set, then do not print messages if invalid parameters given
      /RECURSE - does nothing but kept for compatibility with the
                  Solarsoft version for which recursion is not the default
        http://sohowww.nascom.nasa.gov/solarsoft/gen/idl/struct/tag_exist.pro

Optional Output Keyword


      INDEX = index of matching tag, scalar longward, -1 if tag name does
              not exist

Example


      Determine if the tag 'THICK' is in the !P system variable
     
      IDL> print,tag_exist(!P,'THICK')

Procedure Calls


      None.

Modification History


      Written, C D Pike, RAL, 18-May-94
      Passed out index of matching tag, D Zarro, ARC/GSFC, 27-Jan-95
      William Thompson, GSFC, 6 March 1996 Added keyword TOP_LEVEL
      Zarro, GSFC, 1 August 1996 Added call to help
      Use SIZE(/TNAME) rather than DATATYPE() W. Landsman October 2001
      Added /RECURSE and /QUIET for compatibility with Solarsoft version
                W. Landsman March 2009
      Slightly faster algorithm W. Landsman July 2009
      July 2009 update was not setting Index keyword W. L Sep 2009.
      Use V6.0 notation W.L. Jan 2012
        Not setting index again, sigh W.L./ K. Allers Jan 2012



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