DSL EXPRESSION:
begin{@ox=0}; $d=$x-@ox; @ox=$x


AST:
* statement block
    * begin block
        * statement block
            * assignment "="
                * direct oosvar value "ox"
                * int literal "0"
    * assignment "="
        * direct field value "d"
        * operator "-"
            * direct field value "x"
            * direct oosvar value "ox"
    * assignment "="
        * direct oosvar value "ox"
        * direct field value "x"

a   b   i  x          y          d
pan pan 1  0.34679014 0.72680286 0.34679014
eks pan 2  0.75867996 0.52215111 0.41188982
wye wye 3  0.20460331 0.33831853 -0.55407666
eks wye 4  0.38139939 0.13418874 0.17679609
wye pan 5  0.57328892 0.86362447 0.19188953
zee pan 6  0.52712616 0.49322129 -0.04616276
eks zee 7  0.61178406 0.18788492 0.08465790
zee wye 8  0.59855401 0.97618139 -0.01323005
hat wye 9  0.03144188 0.74955076 -0.56711213
pan wye 10 0.50262601 0.95261836 0.47118413
