10.5.1 Looping Over Structure Elements

A special form of the for statement allows you to loop over all the elements of a structure:

for [ val, key ] = expression
  body
endfor

In this form of the for statement, the value of expression must be a structure. If it is, key and val are set to the name of the element and the corresponding value in turn, until there are no more elements. For example:

x.a = 1
x.b = [1, 2; 3, 4]
x.c = "string"
for [val, key] = x
  key
  val
endfor

     -| key = a
     -| val = 1
     -| key = b
     -| val =
     -|
     -|   1  2
     -|   3  4
     -|
     -| key = c
     -| val = string

The elements are not accessed in any particular order. If you need to cycle through the list in a particular way, you will have to use the function fieldnames and sort the list yourself.