Selecting every other node uing XPATH

Given an arbitrary amount nodes to select:

<root>
  <foo>1</foo>
  <foo>2</foo>
  <foo>3</foo>
  <foo>4</foo>
  <!-- ... -->
<root>

How do I select every other foo so that I get 开发者_JS百科foo[1], foo[3], ... ?

Try

/root/foo[position() mod 2 = 1]

No idea if it will work right, might need 0. I forget if position starts at 0 or 1

position() returns a number that indicates the position of an element relative to other child elements. The mod function returns the „rest“ of a division: 5 mod 2 = 1; 6 mod 2 = 0; 9 mod 2 = 1; 10 mod 2 = 0;

also see: https://en.wiktionary.org/wiki/modulo