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.