PDS_VERSION_ID       = PDS3                                                   
LABEL_REVISION_NOTE          = "2003-09-30 Cornell:carcich"                   
RECORD_TYPE          = STREAM                                                 
OBJECT               = TEXT                                                   
  PUBLICATION_DATE   = 2003-09-30                                             
  NOTE               = "                                                      
    STRUCTURE_README.TXT file for CONTOUR Archive Volume                      
"                                                                             
END_OBJECT                                                                    
END                                                                           
                                                                              
####### File _STRUCTURE_README.TXT_                                           
                                                                              
pro/structure                                                 April 1996      
                                                                              
  This directory contains IDL procedures for working with IDL structure       
variables.    The procedure CREATE_STRUCT will dynamically create an IDL      
structure and is useful when the structure properties are not known before    
run time.   RSI subsequently introduced the intrinsic *function*              
CREATE_STRUCT()                                                               
in IDL V3.6 which has a similar purpose, but requires that each tag value     
be input as a separate parameter.    This makes the intrinisc function awkward
to use when the *number* of tags is not known prior to run time and thus      
the procedure CREATE_STRUCT is being kept in the Library.   The procedure     
MRD_STRUCT is similar to CREATE_STRUCT and was developed for the MRDFITS      
procedure.                                                                    
                                                                              
This directory also contains following IDL routines for working with          
structures, written by Frank Varosi (Hughes STX):                             
                                                                              
                                                                              
  COPY_STRUCT,  struct_FROM,  struct_TO,  NF_copied,  EXCEPT=['except_Tags']  
,$                                                                            
                         /RECUR_FROM     ,$                                   
                         /RECUR_TO     ,$                                     
                         /RECUR_TANDEM                                        
                                                                              
     Copies all Fields with matching Tag names (except for 'except_Tags')     
        from one structure array to a different structure array.              
    Keyword options /RECUR_xxxx will cause recursive calls,                   
        in order to copy from/to nested sub-structures.                       
    NF_copied is incremented by # fields actually copied.                     
                                                                              
                                                                              
                                                                              
  diff_List = COMPARE_STRUCT( struct_A,  struct_B,   EXCEPT=['except_Tags']   
,$                                                                            
                                 /RECUR_A, /RECUR_B   )                       
                                                                              
     Compares all matching Tag names (except for 'except_Tags')               
        between two structure arrays (may be different struct.defs.).         
    Returned Diff_List is a structure containing field names and # diffs.     
                                                                              
                                                                              
                                                                              
  nbytes = SIZE_STRUCT( structure,  /PRINT )                                  
                                                                              
    Obtain the size in bytes of an IDL structure definition.                  
    /PRINT = to print all sub-structure sizes.                                
                                                                              
                                                                              
  ns = N_STRUCT( structure,  Ntags )                                          
                                                                              
    Return number of elements in array, if structured, and number of tags.    
    Returns zero if not structured, also works on file assoc. structs.        
                                                                              
                                                                              
  PRINT_STRUCT,  structure,  ['tags_print'],  LUN_OUT=Lun                     
        Print specified tags from structure (to LUN if given).                
                                                                              
                                                                              
  wsubs = WHERE_TAG( Struct,  Nfound,  TAG_NAME='Tag_Name',  $                
                    ISELECT=ipart,  /NOPRINT,  $                              
                    RANGE=[min,max],  VALUES=[values] )                       
                                                                              
    Obtain subscripts of elements in structure array for which                
    specified Tag has values in a RANGE or matching specified VALUES.         
    Useful in programming when Tag_Name is a variable.