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


AST:
"block" [tt:block] [nt:StatementBlock]
    "begin" [tt:kw_begin] [nt:BeginBlock]
        "block" [tt:block] [nt:StatementBlockInBraces]
            "block" [tt:block] [nt:StatementBlock]
                "=" [tt:equals] [nt:Assignment]
                    "@rsum" [tt:oosvar_name] [nt:DirectOosvarValue]
                    "0" [tt:int_literal] [nt:int_literal]
    "=" [tt:equals] [nt:Assignment]
        "@rsum" [tt:oosvar_name] [nt:DirectOosvarValue]
        "+" [tt:op_plus] [nt:Operator]
            "@rsum" [tt:oosvar_name] [nt:DirectOosvarValue]
            "$x" [tt:field_name] [nt:DirectFieldValue]
    "=" [tt:equals] [nt:Assignment]
        "$rsum" [tt:field_name] [nt:DirectFieldValue]
        "@rsum" [tt:oosvar_name] [nt:DirectOosvarValue]

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
