FUNCTION extract,in_struct
;
; This function accepts a simple structure, i.e., one whose elements are
; scalars, and returns the elements in an array of the same type and the
; appropriate length.
;
len=N_TAGS(in_struct)
typ=SIZE(in_struct.(0))
typ=typ(1)
CASE typ OF
    1:  out=BYTARR(len)
    2:  out=INTARR(len)
    3:  out=LONARR(len)
    4:  out=FLTARR(len)
    5:  out=DBLARR(len)
    6:  out=COMPLEXARR(len)
    ELSE: MESSAGE,"unrecognized type of structure elements"
ENDCASE
FOR i=0,len-1 DO out(i)=in_struct.(i)
RETURN,out
END