;+
;
; @file_comments
; Concatenate 2 structures together. The difference with CREATE_STRUCT 
; is  that if the 2 structure have same elements's name, then mixstru 
; do not break down but choose for the common element the value 
; specified by the first structure.
;
; @categories
; Structure
; 
; @param STRU1 {in}{required}
; Structure which can have same elements's name than 
; STRU2 but with a different value.
;
; @param STRU2 {in}{required}
; Structure which can have same elements's name than 
; STRU1 but with a different value.
;
; @returns
; A structure
;
; @restrictions
; If STRU1 or  STRU2 is not a structure, mixstru send back -1
;
; @examples
;     
;     IDL> a=get_extra(/toto,ok=123)
;     IDL> b=get_extra(ok=111, year=1999, age_capitaine=35)
;     IDL> help, a,b,/struct
;     ** Structure <8334424>, 2 tags, length=4, refs=1:
;        OK              INT            123
;        TOTO            INT              1
;     ** Structure <8373da4>, 3 tags, length=6, refs=1:
;        AGE_CAPITAINE   INT             35
;        OK              INT            111
;        YEAR            INT           1999
;     IDL> help, mixstru(a,b),/struct
;     ** Structure <82f25ac>, 4 tags, length=8, refs=1:
;        AGE_CAPITAINE   INT             35
;        YEAR            INT           1999
;        OK              INT            123
;        TOTO            INT              1
;     IDL> help, mixstru(b,a),/struct
;     ** Structure <834604c>, 4 tags, length=8, refs=1:
;        TOTO            INT              1
;        AGE_CAPITAINE   INT             35
;        OK              INT            111
;        YEAR            INT           1999
;
; @history
; Sebastien Masson (smasson\@lodyc.jussieu.fr)
;                      7/10/1999
;
; @version
; $Id$
;
;-
;
FUNCTION mixstru, stru1, stru2
;
  compile_opt idl2, strictarrsubs
;
@cm_general

   IF size(stru1, /type) EQ 0 AND size(stru2, /type) EQ 8 THEN return, stru2
   IF size(stru2, /type) EQ 0 AND size(stru1, /type) EQ 8 THEN return, stru1
   if size(stru1, /type) NE 8 then return,  -1
   if size(stru2, /type) NE 8 then return,  -1
   tname = tag_names(stru2)
   
   str = ''
   FOR i = 0, n_tags(stru2)-1 DO str = str + tname[i]+' = stru2.(' + strtrim(i, 2)+ '), '

   res = createfunc('get_extra('+str+'_extra = stru1)' $
              , kwdlist = 'stru1 = stru1, stru2 = stru2' $
              , stru1 = stru1, stru2 = stru2 $
              , filename = myuniquetmpdir +'for_createfunc.pro')

   return, res

end