DSL EXPRESSION:
for (i = 0; i < NR; i += 1) { $i += i }


AST:
* statement block
    * triple-for loop "for"
        * statement block
            * assignment "="
                * local variable "i"
                * int literal "0"
        * statement block
            * bare boolean
                * operator "<"
                    * local variable "i"
                    * context variable "NR"
        * statement block
            * assignment "="
                * local variable "i"
                * operator "+"
                    * local variable "i"
                    * int literal "1"
        * statement block
            * assignment "="
                * direct field value "i"
                * operator "+"
                    * direct field value "i"
                    * local variable "i"

