[Haskell-cafe] Tiger compiler in Haskell: annotating abstract syntax tree

[Job Vranish]

Martijn van Steenbergen has a good blog post that describes the method I
generally use:
http://martijn.van.steenbergen.nl/journal/2010/06/24/generically-adding-position-information-to-a-datatype/

In his example he annotates the expression tree with position information,
but you can use the same method to add type annotations, or whatever you
want.

- Job


2010/7/19 José Romildo Malaquias <j.romildo at gmail.com>

> Hello.
>
> In his book "Modern Compilder Implementation in ML", Appel presents a
> compiler project for the Tiger programming language where type checking
> and intermediate code generation are intrinsically coupled.
>
> There is a function
>
>  transExp :: Absyn.Exp -> (Tree.Exp,Types.Type)
>
> that do semantic analysis, translating an expression to the Tree
> intermediate representation language and also do type checking,
> calculating the type of the expression.
>
> Maybe the compiler can be made more didatic if these phases are separate
> phases of compilation.
>
> The type checker would annotate the abstract syntax tree (ast) with type
> annotations, that could be used later by the translater to intermediate
> representation.
>
> In an imperative language probably each relevant ast node would have a
> field for the type annotation, and the type checker would assign the
> type of the node to this field after computing it.
>
> I am writing here to ask suggestions on how to annotate an ast with
> types (or any other information that would be relevant in a compiler
> phase) in Haskell.
>
> As an example, consider the simplified ast types:
>
>  data Exp
>    = IntExp Integer
>    | VarExp Symbol
>    | AssignExp Symbol Exp
>    | IfExp Exp Exp (Maybe Exp)
>    | CallExp Symbol [Exp]
>    | LetExp [Dec] Exp
>
>  data Dec
>     = TypeDec Symbol Ty
>     | FunctionDec Symbol [(Symbol,Symbol)] (Mybe Symbol) Exp
>     | VarDec Symbol (Maybe Symbol) Exp
>
> Expressions can have type annotations, but declarations can not.
>
> Comments?
>
>
> Regards,
>
> Romildo
> --
> Computer Science Department
> Universidade Federal de Ouro Preto, Brasil
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