DSL EXPRESSION:
end{@mean=@sum/@count; emitf @mean}; begin {@count=0; @sum=0.0}; @count=@count+1; @sum=@sum+$x


AST:
"block" [tt:block] [nt:StatementBlock]
    "end" [tt:kw_end] [nt:EndBlock]
        "block" [tt:block] [nt:StatementBlockInBraces]
            "block" [tt:block] [nt:StatementBlock]
                "=" [tt:equals] [nt:Assignment]
                    "@mean" [tt:oosvar_name] [nt:DirectOosvarValue]
                    "/" [tt:op_slash] [nt:Operator]
                        "@sum" [tt:oosvar_name] [nt:DirectOosvarValue]
                        "@count" [tt:oosvar_name] [nt:DirectOosvarValue]
                "emitf" [tt:kw_emitf] [nt:EmitFStatement]
                    "@mean" [tt:oosvar_name] [nt:DirectOosvarValue]
    "begin" [tt:kw_begin] [nt:BeginBlock]
        "block" [tt:block] [nt:StatementBlockInBraces]
            "block" [tt:block] [nt:StatementBlock]
                "=" [tt:equals] [nt:Assignment]
                    "@count" [tt:oosvar_name] [nt:DirectOosvarValue]
                    "0" [tt:int_literal] [nt:int_literal]
                "=" [tt:equals] [nt:Assignment]
                    "@sum" [tt:oosvar_name] [nt:DirectOosvarValue]
                    "0.0" [tt:float_literal] [nt:float_literal]
    "=" [tt:equals] [nt:Assignment]
        "@count" [tt:oosvar_name] [nt:DirectOosvarValue]
        "+" [tt:op_plus] [nt:Operator]
            "@count" [tt:oosvar_name] [nt:DirectOosvarValue]
            "1" [tt:int_literal] [nt:int_literal]
    "=" [tt:equals] [nt:Assignment]
        "@sum" [tt:oosvar_name] [nt:DirectOosvarValue]
        "+" [tt:op_plus] [nt:Operator]
            "@sum" [tt:oosvar_name] [nt:DirectOosvarValue]
            "$x" [tt:field_name] [nt:DirectFieldValue]

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

mean
0.45362938
