XMLSCHEME


<define name="f">
 <lambda args="x">
  <multiply>
   <variable name="x" />
   <funccall func="f">
    <subtract>
     <variable name="x" />
     <int value="1" />
    </substract>
   </funccall>
  </multiply>
 </lambda>
</define>

IT WILL BRING PROGRAMMING TO A WHOLE NEW LEVEL!

What compiler/front end are you using that accepts <multiply> and <subtract> tags? Mine only takes <funccall> (equivalent to <apply>). I'd write it like this:

<define name="f">
 <lambda args="x">
  <apply func="*">
   <variable name="x" />
   <apply func="f">
    <apply func="-">
     <variable name="x" />
     <int value="1" />
    </apply>
   </apply>
  </apply>
 </lambda>
</define>If the function the value of a sub-expression, leave out the func="..." part and the first sub expression is used as the function instead.