DSL EXPRESSION:
$x = 123. + 1e-2 / .2e3 + 1.e-3 + 2e+1


AST:
* statement block
    * assignment "="
        * direct field value "x"
        * operator "+"
            * operator "+"
                * operator "+"
                    * float literal "123."
                    * operator "/"
                        * float literal "1e-2"
                        * float literal ".2e3"
                * float literal "1.e-3"
            * float literal "2e+1"

