DSL EXPRESSION:
begin{@rsum = 0}; @rsum = @rsum + $x; $rsum = @rsum


AST:
* statement block
    * begin block
        * statement block
            * assignment "="
                * direct oosvar value "rsum"
                * int literal "0"
    * assignment "="
        * direct oosvar value "rsum"
        * operator "+"
            * direct oosvar value "rsum"
            * direct field value "x"
    * assignment "="
        * direct field value "rsum"
        * direct oosvar value "rsum"

a   b   i  x          y          rsum
pan pan 1  0.34679014 0.72680286 0.34679014
eks pan 2  0.75867996 0.52215111 1.10547011
wye wye 3  0.20460331 0.33831853 1.31007341
eks wye 4  0.38139939 0.13418874 1.69147281
wye pan 5  0.57328892 0.86362447 2.26476173
zee pan 6  0.52712616 0.49322129 2.79188789
eks zee 7  0.61178406 0.18788492 3.40367195
zee wye 8  0.59855401 0.97618139 4.00222596
hat wye 9  0.03144188 0.74955076 4.03366783
pan wye 10 0.50262601 0.95261836 4.53629384
