(octave.info)Looping Over Structure Elements

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Up: The for Statement

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10.5.1 Looping Over Structure Elements
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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.