[Haskell-cafe] Parsec and (then?) type-check

sam lee skynare at gmail.com
Fri Dec 12 20:27:28 EST 2008

I use my type checking monad, which is separate from Parsec's monad.
So, I can't think of a way to type check during parsing in Parsec's monad.

Anyways, this is what I did:

data Expr = ... | At SourcePos Expr

SourcePos is from Parsec.

Basically, my parse actions will return (At pos e).

And I pass At pos e to typeCheck action.

typeCheck (At pos e) = do
    put pos
    -- typeCheck is in State monad.
    -- in case of error, I'll pos <- get and report source position.
    typeCheck e

typeCheck (Variable a) = do

check out this:

On Fri, Dec 12, 2008 at 5:06 PM, Greg Fitzgerald <garious at gmail.com> wrote:
> Parser gurus,
> When you write a parser with a library like Parsec, do you typically
> type-check while parsing, or afterward in a separate pass?  The latter
> is more modular, but it means labeling every element in the AST with
> the parser position so that you can give good error messages.  Do you
> find the added modularity worth the hassle or just pack type-checking
> into the parser pass?
> Thanks,
> Greg
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