Identifier     chk_tag

 Purpose        Check whether a given structure containes a particular tag

 Synopsis       status = chk_tag(struc_in, tagnames)

 Arguments      Name      I/O  Type      Description
                -----------------------------------------------------
                struc_in   I   struct    The input structure to be searched
                                         for the tag tagname
                tagnames   I   string/   The tag name(s) to be searched in
                               strarr    struc_in
                
 Returns        integer or intarr: 1 if struc_in contains the tag tagname, 
                                   2 if not

 Description    ---

 Comment        ---

 Example        status = chk_tag(saar.data,'flux')
                         if saar contains .flux: status = 1,else 2

                status = chk_tag(saar.data,['wave','flag'])
                         if saar.data contains .wave but not .flag this
                         yields status = [1, 2] 

 Dependencies   CALLS:       --
                CALLED FROM: arithm (general auxillary routine)

 Category       ISAP

 Filename       chk_tag.pro

 Author         E. Sturm (--> ES)

 Version        1.0

 History        0.1   14-09-95  ES    
                1.0   30-11-95  ES  V1 delivery
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Copyright (C) 1995, Max-Planck-Institut fuer extraterrestrische Physik (MPE);
                    Garching, Germany                                       ;
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