Parenthesis are needed

Messages > Parenthesis are needed

You get the warning: Parenthesis are needed, if the first semantic action contains a variable declaration for the whole production, for productions of the kind

{-...-}

A | B ...

Frequently the first semantic action contains declarations of variables, which shall be used in all alternatives. But then, you have to put the alternatives into parenthesis. E.g.:

{- str s; -}

(

"a" | "b"

)

{-return s;-}

Without parenthesis

{- str s; -}

"a"

| "b"

{-return s;-}

you get the error message:

Unknown identifier: s

for {-return s;-}, because there are implicit parenthesis like

(

{- str s; -}

"a"

)

|

(

"b"

{-return s;-}

)

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