Querying the instances a data type implements
Hi, I am trying query the instances that a data type implements. Calling reify on the data type doesn't appear to return anything relating to type classes. I am very new to Template Haskell, so I apologize if there is a easy way to do this that I missed. -Jonathan
On Sun, Jan 17, 2010 at 6:42 PM,
Hi,
I am trying query the instances that a data type implements. Calling reify on the data type doesn't appear to return anything relating to type classes.
I am very new to Template Haskell, so I apologize if there is a easy way to do this that I missed.
-Jonathan
I do not believe that this is possible (getting instances based on type). It, I suppose, would be possible theoretically to get at least instances in-scope, but, as type classes are open, this wouldn't, necessarily, be all type classes the date type implements. But I don't believe there's any support for navigating to instances from types. As an aside, you'd be better off sending queries about Template Haskell to the haskell-cafe@haskell.org mailing list, as this (TH) mailing list is very lightly used and there's been talk of getting rid of it. Probably anybody subscribed to this list is also subscribed to Haskell Cafe as well.
All: as Robert says, I keep meaning to close the template-haskell list altogether; but I am not sure how to do so. Jonathan: where did you find a pointer to the mailing list? I should remove those too. Returning to the question, sadly there's no way to do what you want right now. There's an open feature request: http://hackage.haskell.org/trac/ghc/ticket/1835 Would anyone like to undertake it? It's not hard. Simon From: template-haskell-bounces@haskell.org [mailto:template-haskell-bounces@haskell.org] On Behalf Of jonathanGfischoff@gmail.com Sent: 17 January 2010 23:42 To: template-haskell@haskell.org Subject: [Template-haskell] Querying the instances a data type implements Hi, I am trying query the instances that a data type implements. Calling reify on the data type doesn't appear to return anything relating to type classes. I am very new to Template Haskell, so I apologize if there is a easy way to do this that I missed. -Jonathan
I got the link from the Template Haskell Wiki page.
It is possible that I might have time to work on the feature myself. I don't
it, but if that is the case I will let you know.
-Jonathan
On Mon, Jan 18, 2010 at 1:55 AM, Simon Peyton-Jones
All: as Robert says, I keep meaning to close the template-haskell list altogether; but I am not sure how to do so.
Jonathan: where did you find a pointer to the mailing list? I should remove those too.
Returning to the question, sadly there’s no way to do what you want right now. There’s an open feature request:
http://hackage.haskell.org/trac/ghc/ticket/1835
Would anyone like to undertake it? It’s not hard.
Simon
*From:* template-haskell-bounces@haskell.org [mailto: template-haskell-bounces@haskell.org] *On Behalf Of * jonathanGfischoff@gmail.com *Sent:* 17 January 2010 23:42 *To:* template-haskell@haskell.org *Subject:* [Template-haskell] Querying the instances a data type implements
Hi,
I am trying query the instances that a data type implements. Calling reify on the data type doesn't appear to return anything relating to type classes.
I am very new to Template Haskell, so I apologize if there is a easy way to do this that I missed.
-Jonathan
participants (4)
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Jonathan Fischoff -
jonathanGfischoff＠gmail.com
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Robert Greayer -
Simon Peyton-Jones