vcol2arr.pro

pro vcol2arr, vcol, arr

  ;; Non-structures are returned immediately
  sz = size(vcol)
  if sz(sz(0)+1) NE 8 then begin
      arr = temporary(vcol)
      return
  endif

  tn = tag_names(vcol)
  wh = where(tn EQ 'VARICOL', ct)
  if ct EQ 0 then $
    message, 'ERROR: VCOL is not a variable-length array structure'

  ;; Extract the relevant information from the structure before
  ;; destroying it.
  type = vcol.type
  ii = vcol.indices
  nc = ii(1:*) - ii
  ncols = max(nc)
  nrows = vcol.n_rows
  mm = (temporary(vcol)).data

  ;; Make new array
  arr = make_array(ncols, nrows, type=type)

  ;; Fill new array, either by row or by column, whichever uses fewer
  ;; iterations.  Either way produces the same results.
  if ncols LT nrows then begin
      for i = 0, ncols-1 do begin
          wh = where(nc GT i)
          arr(i,wh) = mm(ii(wh)+i)
      endfor
  endif else begin
      for i = 0, nrows-1 do if nc(i) GT 0 then arr(0,i) = mm(ii(i):ii(i+1)-1)
  endelse
  
end