CREATE_STRUCT

       Create an IDL structure from a list of tag names and dimensions

       Dynamically create an IDL structure variable from list of tag names
       and data types of arbitrary dimensions.   Useful when the type of
       structure needed is not known until run time.
       Unlike the intrinsic function CREATE_STRUCT(), this procedure does not
       require the user to know the number of tags before run time.   (Note
       there is no name conflict since the intrinsic CREATE_STRUCT is a
       function, and this file contains a procedure.)

       CREATE_STRUCT, STRUCT, strname, tagnames, tag_descript,
                             [ DIMEN = , /CHATTER, /NODELETE ]

       STRNAME -   name to be associated with structure (string)
               Must be unique for each structure created.   Set
               STRNAME = '' to create an anonymous structure
       TAGNAMES -  tag names for structure elements
               (string or string array)
       TAG_DESCRIPT -  String descriptor for the structure, containing the
               tag type and dimensions.  For example, 'A(2),F(3),I', would
               be the descriptor for a structure with 3 tags, strarr(2),
               fltarr(3) and Integer scalar, respectively.
               Allowed types are 'A' for strings, 'B' or 'L' for unsigned byte
               integers, 'I' for integers, 'J' for longword integers,
               'F' or 'E' for floating point, 'D' for double precision
               'C' for complex, and 'M' for double complex
               Uninterpretable characters in a format field are ignored.
               For vectors, the tag description can also be specified by
               a repeat count.  For example, '16E,2J' would specify a
               structure with two tags, fltarr(16), and lonarr(2)

       DIMEN -    number of dimensions of structure array (default is 1)
       CHATTER -  If /CHATTER is set, then CREATE_STRUCT will display
                  the dimensions of the structure to be created, and prompt
                  the user whether to continue.  Default is no prompt.
       NODELETE - If /NODELETE is set, then the temporary file created
                  CREATE_STRUCT will not be deleted upon exiting.   See below

       STRUCT -   IDL structure, created according to specifications

       IDL> create_struct, new, 'name',['tag1','tag2','tag3'], 'D(2),F,A(1)'
       will create a structure variable new, with structure name NAME
       To see the structure of new:
       IDL> help,new,/struc
       ** Structure NAME, 3 tags, 20 length:
          TAG1            DOUBLE         Array(2)
          TAG2            FLOAT          0.0
          TAG3            STRING         Array(1)

       Generates a temporary procedure file using input information with
       the desired structure data types and dimensions hard-coded.
       This file is then executed with CALL_PROCEDURE.

       If CREATE_STRUCT cannot write a temporary .pro file in the current
       directory, then it will write the temporary file in the getenv('HOME')
       directory.
       At present, can fail if a tag_name cannot be used as a proper
       structure component definition, e.g., '0.10' will not
       work, but a typical string like 'RA' or 'DEC' will.
       A partial workaround checks for characters '\' and '/'
       and '.' and converts them to '_'. in a tag_name.
       Note that 'L' now specifies a LOGICAL (byte) data type and not a
       a LONG data type for consistency with FITS binary tables

       The name of the structure must be unique, for each structure created.
       Otherwise, the new variable will have the same structure as the
       previous definition (because the temporary procedure will not be
       recompiled).  ** No error message will be generated  ***

       FDECOMP, REPCHR()

       Version 1.0 RAS January 1992
       Modified 26 Feb 1992 for Rosat IDL Library (GAR)
       Modified Jun 1992 to accept arrays for tag elements -- KLV, Hughes STX
       Accept anonymous structures W. Landsman  HSTX    Sep. 92
       Accept 'E' and 'J' format specifications   W. Landsman Jan 93
       'L' format now stands for logical and not long array
       Accept repeat format for vectors        W. Landsman Feb 93
       Accept complex and double complex (for V4.0)   W. Landsman Jul 95
       Work for long structure definitions  W. Landsman Aug 97
       Converted to IDL V5.0   W. Landsman   September 1997
       Write temporary file in HOME directory if necessary  W. Landsman Jul 98
       Use OPENR,/DELETE for OS-independent file removal W. Landsman Jan 99
       Use STRSPLIT() instead of GETTOK() W. Landsman  July 2002
       Assume since V5.3 W. Landsman  Feb 2004
       Added RESOLVE_ROUTINE to ensure recompilation W. Landsman Sep. 2004

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