Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/~valenti/idl/struct_replace_field.pro Дата изменения: Wed Jun 22 06:07:45 2011 Дата индексирования: Sun Mar 2 00:00:00 2014 Кодировка: Поисковые слова: trees

pro struct_replace_field, struct, tag, data, newtag=newtag
;Change the type, dimensionality, and contents of an existing structure
; field. The tag name may be changed in the process.
;
;Inputs:
; tag (string) Case insensitive tag name describing structure field to
; modify. Leading and trailing spaces will be ignored. If the field does
; not exist, the structure is not changed and an error is reported.
; data (any) data that will replace current contents of
; [newtag=] (string) new tag name for field being replaced. If not
; specified, the original tag name will be retained.
;
;Input/Output:
; struct (structure) structure to be modified.
;
;Examples:
;
; Replace sme.wave with the arbitrary contents of wave:
;
; IDL> struct_replace_field, sme, 'wave', wave
;
; The tag name for a field can be changed without altering the data:
;
; IDL> struct_replace_field, clients, 'NMAE', clients.nmae, newtag='Name'
;
;History:
; 2003-Jul-20 Valenti Initial coding

if n_params() lt 3 then begin
print, 'syntax: struct_replace_field, struct, tag, data [,newtag=]'
return
endif

;Check that input is a structure.
if size(struct, /tname) ne 'STRUCT' then begin
message, 'first argument is not a structure'
endif

;Get list of structure tags.
tags = tag_names(struct)
ntags = n_elements(tags)

;Check that requested field exists in input structure.
ctag = strupcase(strtrim(tag, 2)) ;canoncial form of tag
itag = where(tags eq ctag, nmatch)
if nmatch eq 0 then begin
message, 'structure does not contain ' + ctag + ' field'
return
endif
itag = itag[0] ;convert to scalar

;Choose tag name for the output structure.
if keyword_set(newtag) then otag = newtag else otag = ctag

;Copy any fields that precede target field. Then add target field.
if itag eq 0 then begin ;target field occurs first
new = create_struct(otag, data)
endif else begin ;other fields before target
new = create_struct(tags[0], struct.(0)) ;initialize structure
for i=1, itag-1 do begin ;insert leading unchange
new = create_struct(new, tags[i], struct.(i))
endfor
new = create_struct(new, otag, data) ;insert new data
endelse

;Replicate remainder of structure after desired tag.
for i=itag+1, ntags-1 do begin
new = create_struct(new, tags[i], struct.(i))
endfor

;Replace input structure with new structure.
struct = new

end