indexing over structure tags

[Randall Skelton <rhskelto(at)atm.ox.ac.uk>]

Hello,

Imagine someone has a structure of structures...

  ; define the basic structure for each 
  sm_struc = {basic_struct, comment: ' ', values: fltarr(nlev)}
  
  ; define the large structure
  data = {big_struct, so4: sm_struc, co2: sm_struc, hcl: sm_struc}

The IDL manual describes how to make an array of the tags in a structure
using:

  ; get the names of the tags
  names = tag_names(data)

so that names = [so4, co2, hcl].

That is all fine.  But is it possible to index over the tag names with a
for-loop?

i.e.   for i=0, n_elements(names)-1 do data.names[i].values = i
                                       ^^^^^^^^^^^^^^^^^^^^

where IDL determines what the appropriate label 'data.name[i].values' is.  

Thanks,
Randall