Up: The for Statement [Contents][Index]
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.