On Tue, Jul 20, 2010 at 11:06,
<oleg@okmij.org> wrote:
Jose' Romildo Malaquias wrote:
> 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.
There is also a general way of annotating AST post factum, described in
http://okmij.org/ftp/Algorithms.html#tree-annot
The method lets one attach arbitrarily many annotations to an already
built AST, *without* the need to change the definition of the
datatype. One does not even have to anticipate annotations! The method
would work with your AST
> data Exp
> = IntExp Integer
> | VarExp Symbol
> | AssignExp Symbol Exp
as _it is_, without any modifications -- neither to the data type
definition, nor to the tree.
The method was demonstrated when writing a compiler of sorts:
annotating an AST with an inferred type for each node. If the type
inference fails, we can still print out the inferred types for the
good subexpressions.