Dear Joachim, You are right -- some more context. Given tc :: TyCon m :: ModName env :: HscEnv I want to get a s :: String such that _in_ the context given by `m` and `env` I can resolve `s` to get back the original `TyCon`, e.g. something like L _ rn <- hscParseIdentifier env s name <- lookupRdrName env modName rn would then return `name :: Name` which corresponds to the original `TyCon`. That is, the goal is _not_ pretty printing, but "serialization" into a String representation that lets me recover the original `TyCon` later. (Consequently, `"Data.Set.Base.Set"` doesn't work as the `Data.Set.Base` module is hidden and hence, when I try the above, GHC complains that the name is not in scope. Does that clarify the problem? Thanks! - Ranjit. On Tue, Jan 24, 2017 at 6:11 PM, Joachim Breitner wrote:

Hi Ranjit,

Am Dienstag, den 24.01.2017, 16:09 -0800 schrieb Ranjit Jhala:

...

My goal is to write a function

tyconString :: TyCon -> String

(perhaps with extra parameters) such that given the `TyCon` corresponding to `Set`, I get back the "original" name `S.Set`, or even `Data.Set.Set`.

Everything I've tried, which is fiddling with different variants of `PprStyle`, end up giving me `Data.Set.Base.Set`

Does anyone have a suggestion for how to proceed?

in a way, `Data.Set.Base.Set` is the “original”, proper name for Set, everything else is just a local view on the name.

So, are you maybe looking for a way to get the “most natural way” to print a name in a certain module context?

This functionality must exist somewhere, as ghci is printing out errors this way. But it certainly would require an additional argument to tyconString, to specify in which module to print the name.

Greetings, Joachim

-- Joachim “nomeata” Breitner mail@joachim-breitner.de • https://www.joachim-breitner.de/ XMPP: nomeata@joachim-breitner.de • OpenPGP-Key: 0xF0FBF51F Debian Developer: nomeata@debian.org _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users

@Simon, The route you outline was the one we already use -- but that gives back the full name "Data.Set.Base.Set" (instead of "S.Set" or "Data.Set.Set"), as the module is "Data.Set.Base". @Edward, Yes, I think your suggestion should work! This business of determining which packages/modules are hidden is exactly what we are trying to get around. (In this case, Data.Set.Base is hidden...) Thanks all! - Ranjit. On Wed, Jan 25, 2017 at 1:00 AM, Edward Z. Yang wrote:

Hi Ranjit,

Unfortunately you need more information to do this, since the set of modules which are available for import can vary depending on whether or not packages are hidden or not (not even counting whether or not a module is exposed or not!)

The way GHC's pretty printer gives a good name is that it keeps track of all of the names in scope and where they came from in a GlobalRdrEnv. The relevant code is in 'mkPrintUnqualified' in HscTypes, but if you pretty print using user-style with an appropriately set up GlobalRdrEnv you should get the things you want.

Edward

Excerpts from Ranjit Jhala's message of 2017-01-24 19:00:05 -0800:

...

Dear Joachim,

You are right -- some more context.

Given

tc :: TyCon m :: ModName env :: HscEnv

I want to get a

s :: String

such that _in_ the context given by `m` and `env` I can resolve `s` to get back the original `TyCon`, e.g. something like

L _ rn <- hscParseIdentifier env s name <- lookupRdrName env modName rn

would then return `name :: Name` which corresponds to the original `TyCon`.

That is, the goal is _not_ pretty printing, but "serialization" into a String representation that lets me recover the original `TyCon` later.

(Consequently, `"Data.Set.Base.Set"` doesn't work as the `Data.Set.Base` module is hidden and hence, when I try the above, GHC complains that the name is not in scope.

Does that clarify the problem?

Thanks!

- Ranjit.

On Tue, Jan 24, 2017 at 6:11 PM, Joachim Breitner < mail@joachim-breitner.de> wrote:

...

Hi Ranjit,

Am Dienstag, den 24.01.2017, 16:09 -0800 schrieb Ranjit Jhala:

...

My goal is to write a function

tyconString :: TyCon -> String

(perhaps with extra parameters) such that given the `TyCon` corresponding to `Set`, I get back the "original" name `S.Set`, or even `Data.Set.Set`.

Everything I've tried, which is fiddling with different variants of `PprStyle`, end up giving me `Data.Set.Base.Set`

Does anyone have a suggestion for how to proceed?

in a way, `Data.Set.Base.Set` is the “original”, proper name for Set, everything else is just a local view on the name.

So, are you maybe looking for a way to get the “most natural way” to print a name in a certain module context?

This functionality must exist somewhere, as ghci is printing out errors this way. But it certainly would require an additional argument to tyconString, to specify in which module to print the name.

Greetings, Joachim

-- Joachim “nomeata” Breitner mail@joachim-breitner.de • https://www.joachim-breitner.de/ XMPP: nomeata@joachim-breitner.de • OpenPGP-Key: 0xF0FBF51F Debian Developer: nomeata@debian.org _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users