Instantiating a type with fresh, flexi type variables
For my pattern-synonyms branch (see prev. email) I had to write the following function, incl. making TcValidity.fvTypes public: tcInstTypes :: [TcType] -> TcM [TcType] tcInstTypes tys = do { let tvs = fvTypes tys ; (_, _, subst) <- tcInstTyVars tvs ; return $ map (substTy subst) tys } I'm surprised I had to write this myself, and this made me wonder if there's a much better way to handle cases where I have some kind of definition which has some inferred type, and then various use sites of that definition must all have types that can be unified with this original inferred type. Is there? Thanks, Gergo
I'm a bit puzzled that you don't have a *quantified* type, something like forall abc. ty1 -> ... -> tyn -> ty to instantiate. I'm a bit suspicious about instantiating all the random free variables of a type (or types). We should talk now I'm back in circulation. What time zone are you in? What's your skype id? (Mine is simonpj0) simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Dr. ERDI | Gergo | Sent: 08 August 2013 18:37 | To: ghc-devs@haskell.org | Subject: Instantiating a type with fresh, flexi type variables | | For my pattern-synonyms branch (see prev. email) I had to write the | following function, incl. making TcValidity.fvTypes public: | | tcInstTypes :: [TcType] -> TcM [TcType] | tcInstTypes tys | = do { let tvs = fvTypes tys | ; (_, _, subst) <- tcInstTyVars tvs | ; return $ map (substTy subst) tys } | | I'm surprised I had to write this myself, and this made me wonder if | there's a much better way to handle cases where I have some kind of | definition which has some inferred type, and then various use sites | of that definition must all have types that can be unified with this | original inferred type. | Is there? | | Thanks, | Gergo | | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs
Hi Simon,
Here's what I wrote earlier about this to someone who contacted me in
private (name withheld because I don't know why he contacted me off-list):
"""
So the code in question is this:
https://github.com/gergoerdi/ghc/commit/f874f8#L5R749
and the part that feels fishy to me is tcInstTypes, both the implementation
and the fact that I have to take care of this manually. I guess the right
solution would involve doing something differently in
https://github.com/gergoerdi/ghc/commit/244b9#L3R43
so that the types in "rhs_ty" and "args" are correctly generalized. But I
haven't been able to find out how that would be done.
"""
I'm replying to your other questions in a separate, private mail.
Thanks,
Gergo
On Aug 20, 2013 6:14 AM, "Simon Peyton-Jones"
I'm a bit puzzled that you don't have a *quantified* type, something like forall abc. ty1 -> ... -> tyn -> ty to instantiate. I'm a bit suspicious about instantiating all the random free variables of a type (or types). We should talk now I'm back in circulation. What time zone are you in? What's your skype id? (Mine is simonpj0)
simon
| -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Dr. ERDI | Gergo | Sent: 08 August 2013 18:37 | To: ghc-devs@haskell.org | Subject: Instantiating a type with fresh, flexi type variables | | For my pattern-synonyms branch (see prev. email) I had to write the | following function, incl. making TcValidity.fvTypes public: | | tcInstTypes :: [TcType] -> TcM [TcType] | tcInstTypes tys | = do { let tvs = fvTypes tys | ; (_, _, subst) <- tcInstTyVars tvs | ; return $ map (substTy subst) tys } | | I'm surprised I had to write this myself, and this made me wonder if | there's a much better way to handle cases where I have some kind of | definition which has some inferred type, and then various use sites | of that definition must all have types that can be unified with this | original inferred type. | Is there? | | Thanks, | Gergo | | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs
Yes I suspect that patSynSig should return three results: the quantified tyvars, the lhs types and the rhs type
Simon
From: Dr. ÉRDI Gergő [mailto:gergo@erdi.hu]
Sent: 20 August 2013 03:09
To: Simon Peyton-Jones
Cc: ghc-devs@haskell.org
Subject: RE: Instantiating a type with fresh, flexi type variables
Hi Simon,
Here's what I wrote earlier about this to someone who contacted me in private (name withheld because I don't know why he contacted me off-list):
"""
So the code in question is this:
https://github.com/gergoerdi/ghc/commit/f874f8#L5R749
and the part that feels fishy to me is tcInstTypes, both the implementation and the fact that I have to take care of this manually. I guess the right solution would involve doing something differently in
https://github.com/gergoerdi/ghc/commit/244b9#L3R43
so that the types in "rhs_ty" and "args" are correctly generalized. But I haven't been able to find out how that would be done.
"""
I'm replying to your other questions in a separate, private mail.
Thanks,
Gergo
On Aug 20, 2013 6:14 AM, "Simon Peyton-Jones"
participants (3)
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Dr. ERDI Gergo -
Dr. ÉRDI Gergő
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Simon Peyton-Jones