Re: [commit: ghc] master: Add :info! to GHCi. This shows all instances without filtering first. (2ec32a8)
On 03/12/12 20:13, Iavor Diatchki wrote:
Hello,
On Mon, Dec 3, 2012 at 8:44 AM, Simon Marlow marlo...@gmail.com
mailto:marlo...@gmail.com wrote:
OI know that Accessor has an Applicative instace because the operations
work. I'd like to find the instance, so I can see how it works,
so I try:
Ok, so this is a bug: you shouldn't be able to use the instance
because it isn't in scope. If this was a source file, then GHC
would complain that the instance was not in scope.
The bug is (sort of) documented in the Known Bugs section of the
user guide, although the documentation incorrectly says that it also
affects --make, which it doesn't (I'll fix it).
I don't think that this is the bug to blame: the instance is in scope,
it is just that it is being filtered by :info.
Here is an example:
module Test where
import Control.Applicative (pure)
import Control.Lens
example :: Accessor () ()
example = pure ()
This works just fine. I think the issue is as follows. The
`Applicative` instance for `Accessor` is like this:
instance Monoid r = Applicative (Accessor r)
Now, on the GHCi command line `Accessor` and `Applicative` are in scope
but `Monoid` is not. However, there are instances of `Monoid` for
various datatypes (e.g., ()) that are also in scope, so that instance is
actually usable.
Ah, I see. Sp that suggests a better fix: the new :info! should display
all instances that are in scope, in contrast to the ordinary :info which
displays only instances involving types and classes that are in scope.
As far as I understand, the current plausiblity check filters out any
instances that contain tycons that are not in-scope, which is why this
particular instance does not show up. It looks like in some cases this
is too aggressive.
So I don't really object to having this feature, as long as we say
clearly in the documentation that it doesn't have a well-specified
behaviour, and the instances it shows may or may not actually be
available. (if we fix the bug, many of them won't be available, but
it might be useful to find out where to get them from).
Would you mind updating the docs, and close #5998?
Yeah, I'd be happy to do that. Which documentation should I update?
The GHCi docs (docs/users_guide/ghci.xml) to add the new command.
Cheers,
Simon
-Iavor
Cheers,
Simon
Prelude Control.Applicative Control.Lens :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor
{Control.Lens.Internal.__runAccessor :: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal’
Weird, it doesn’t show up, so what are the instances of
`Applicative`?
Prelude Control.Applicative Control.Lens :i Applicative
class Functor f = Applicative f where
pure :: a - f a
(*) :: f (a - b) - f a - f b
(*) :: f a - f b - f b
(*) :: f a - f b - f a
-- Defined in `Control.Applicative'
instance Applicative [] -- Defined in `Control.Applicative'
instance Applicative ZipList -- Defined in `Control.Applicative'
instance Monad m = Applicative (WrappedMonad m)
-- Defined in `Control.Applicative'
instance Applicative Maybe -- Defined in `Control.Applicative'
instance Applicative IO -- Defined in `Control.Applicative'
instance Applicative (Either e) -- Defined in `Control.Applicative'
instance Applicative ((-) a) -- Defined in `Control.Applicative'
instance Applicative Mutator -- Defined in `Control.Lens.Internal'
instance Applicative (Bazaar a b)
-- Defined in `Control.Lens.Internal’
It does not show up, but I'm sure that there is an instance as the
operations seem to work! It turns out that the only way to find the
instance is to not only already know that there is one and
import the
appropriate module, but to also import the modules used in the
context.
But if I already knew all of this I wouldn't have asked GHCi.
Prelude Control.Applicative Control.Lens import Data.Monoid
Prelude Control.Applicative Control.Lens Data.Monoid :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor
{Control.Lens.Internal.__runAccessor :: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
*instance Monoid r = Applicative (Accessor r)*
-- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal'
In contrast, with :info! we get everything that GHCi knows
about, so
it is quite easy to
Re: [commit: ghc] master: Add :info! to GHCi. This shows all instances without filtering first. (2ec32a8)
On 30/11/12 18:25, Iavor Diatchki wrote:
Hello Simon,
there was no discussion because I thought that this would be completely
uncontroversial since: (i) it does not change the current behavior, and
(ii) it adds new functionality which is quite useful.
Here is the use case that motivated me to implement this (described by
Eric Mertens, cc-ed on this e-mail). The example uses the `lens` package.
I know that Accessor has an Applicative instace because the operations
work. I'd like to find the instance, so I can see how it works, so I try:
Ok, so this is a bug: you shouldn't be able to use the instance because
it isn't in scope. If this was a source file, then GHC would complain
that the instance was not in scope.
The bug is (sort of) documented in the Known Bugs section of the user
guide, although the documentation incorrectly says that it also affects
--make, which it doesn't (I'll fix it).
So I don't really object to having this feature, as long as we say
clearly in the documentation that it doesn't have a well-specified
behaviour, and the instances it shows may or may not actually be
available. (if we fix the bug, many of them won't be available, but it
might be useful to find out where to get them from).
Would you mind updating the docs, and close #5998?
Cheers,
Simon
Prelude Control.Applicative Control.Lens :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor {Control.Lens.Internal.runAccessor :: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal’
Weird, it doesn’t show up, so what are the instances of `Applicative`?
Prelude Control.Applicative Control.Lens :i Applicative
class Functor f = Applicative f where
pure :: a - f a
(*) :: f (a - b) - f a - f b
(*) :: f a - f b - f b
(*) :: f a - f b - f a
-- Defined in `Control.Applicative'
instance Applicative [] -- Defined in `Control.Applicative'
instance Applicative ZipList -- Defined in `Control.Applicative'
instance Monad m = Applicative (WrappedMonad m)
-- Defined in `Control.Applicative'
instance Applicative Maybe -- Defined in `Control.Applicative'
instance Applicative IO -- Defined in `Control.Applicative'
instance Applicative (Either e) -- Defined in `Control.Applicative'
instance Applicative ((-) a) -- Defined in `Control.Applicative'
instance Applicative Mutator -- Defined in `Control.Lens.Internal'
instance Applicative (Bazaar a b)
-- Defined in `Control.Lens.Internal’
It does not show up, but I'm sure that there is an instance as the
operations seem to work! It turns out that the only way to find the
instance is to not only already know that there is one and import the
appropriate module, but to also import the modules used in the context.
But if I already knew all of this I wouldn't have asked GHCi.
Prelude Control.Applicative Control.Lens import Data.Monoid
Prelude Control.Applicative Control.Lens Data.Monoid :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor {Control.Lens.Internal.runAccessor :: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
*instance Monoid r = Applicative (Accessor r)*
-- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal'
In contrast, with :info! we get everything that GHCi knows about, so
it is quite easy to figure out what's going on.
-Iavor
On Fri, Nov 30, 2012 at 3:42 AM, Simon Marlow marlo...@gmail.com
mailto:marlo...@gmail.com wrote:
On 30/11/12 02:03, Iavor Diatchki wrote:
Repository : ssh://darcs.haskell.org//srv/__darcs/ghc
http://darcs.haskell.org//srv/darcs/ghc
On branch : master
http://hackage.haskell.org/__trac/ghc/changeset/__2ec32a8e1cb323b230b0c228dbee31__3647892bf4
http://hackage.haskell.org/trac/ghc/changeset/2ec32a8e1cb323b230b0c228dbee313647892bf4
--__--__---
commit 2ec32a8e1cb323b230b0c228dbee31__3647892bf4
Author: Iavor S. Diatchki diatc...@galois.com
mailto:diatc...@galois.com
Date: Thu Nov 29 17:14:48 2012 -0800
Add :info! to GHCi. This shows all instances without
filtering first.
The default behavior of :info is to show only those
instances of
for a type, where all relevant type constructor names are
in scope.
This keeps down the number of instances shown to the user.
In some cases, it is nice to be able to see all instances
for a type.
This patch implements this with the :info! command.
Was there some discussion about this? The last I remember was this:
http://hackage.haskell.org/__trac/ghc/ticket/5998
http://hackage.haskell.org/trac/ghc/ticket/5998
where we decided
Re: [commit: ghc] master: Add :info! to GHCi. This shows all instances without filtering first. (2ec32a8)
Hello,
On Mon, Dec 3, 2012 at 8:44 AM, Simon Marlow marlo...@gmail.com wrote:
OI know that Accessor has an Applicative instace because the operations
work. I'd like to find the instance, so I can see how it works, so I try:
Ok, so this is a bug: you shouldn't be able to use the instance because it
isn't in scope. If this was a source file, then GHC would complain that
the instance was not in scope.
The bug is (sort of) documented in the Known Bugs section of the user
guide, although the documentation incorrectly says that it also affects
--make, which it doesn't (I'll fix it).
I don't think that this is the bug to blame: the instance is in scope, it
is just that it is being filtered by :info.
Here is an example:
module Test where
import Control.Applicative (pure)
import Control.Lens
example :: Accessor () ()
example = pure ()
This works just fine. I think the issue is as follows. The `Applicative`
instance for `Accessor` is like this:
instance Monoid r = Applicative (Accessor r)
Now, on the GHCi command line `Accessor` and `Applicative` are in scope but
`Monoid` is not. However, there are instances of `Monoid` for various
datatypes (e.g., ()) that are also in scope, so that instance is actually
usable.
As far as I understand, the current plausiblity check filters out any
instances that contain tycons that are not in-scope, which is why this
particular instance does not show up. It looks like in some cases this is
too aggressive.
So I don't really object to having this feature, as long as we say
clearly in the documentation that it doesn't have a well-specified
behaviour, and the instances it shows may or may not actually be available.
(if we fix the bug, many of them won't be available, but it might be useful
to find out where to get them from).
Would you mind updating the docs, and close #5998?
Yeah, I'd be happy to do that. Which documentation should I update?
-Iavor
Cheers,
Simon
Prelude Control.Applicative Control.Lens :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor {Control.Lens.Internal.**runAccessor
:: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal’
Weird, it doesn’t show up, so what are the instances of `Applicative`?
Prelude Control.Applicative Control.Lens :i Applicative
class Functor f = Applicative f where
pure :: a - f a
(*) :: f (a - b) - f a - f b
(*) :: f a - f b - f b
(*) :: f a - f b - f a
-- Defined in `Control.Applicative'
instance Applicative [] -- Defined in `Control.Applicative'
instance Applicative ZipList -- Defined in `Control.Applicative'
instance Monad m = Applicative (WrappedMonad m)
-- Defined in `Control.Applicative'
instance Applicative Maybe -- Defined in `Control.Applicative'
instance Applicative IO -- Defined in `Control.Applicative'
instance Applicative (Either e) -- Defined in `Control.Applicative'
instance Applicative ((-) a) -- Defined in `Control.Applicative'
instance Applicative Mutator -- Defined in `Control.Lens.Internal'
instance Applicative (Bazaar a b)
-- Defined in `Control.Lens.Internal’
It does not show up, but I'm sure that there is an instance as the
operations seem to work! It turns out that the only way to find the
instance is to not only already know that there is one and import the
appropriate module, but to also import the modules used in the context.
But if I already knew all of this I wouldn't have asked GHCi.
Prelude Control.Applicative Control.Lens import Data.Monoid
Prelude Control.Applicative Control.Lens Data.Monoid :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor {Control.Lens.Internal.**runAccessor
:: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
*instance Monoid r = Applicative (Accessor r)*
-- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal'
In contrast, with :info! we get everything that GHCi knows about, so
it is quite easy to figure out what's going on.
-Iavor
On Fri, Nov 30, 2012 at 3:42 AM, Simon Marlow marlo...@gmail.com
mailto:marlo...@gmail.com wrote:
On 30/11/12 02:03, Iavor Diatchki wrote:
Repository :
ssh://darcs.haskell.org//srv/_**_darcs/ghchttp://darcs.haskell.org//srv/__darcs/ghc
http://darcs.haskell.org//**srv/darcs/ghchttp://darcs.haskell.org//srv/darcs/ghc
On branch : master
http://hackage.haskell.org/__**trac/ghc/changeset/__**
2ec32a8e1cb323b230b0c228dbee31**__3647892bf4http://hackage.haskell.org/__trac/ghc/changeset/__2ec32a8e1cb323b230b0c228dbee31__3647892bf4
http://hackage.haskell.org/**trac/ghc/changeset/**
Re: [commit: ghc] master: Add :info! to GHCi. This shows all instances without filtering first. (2ec32a8)
On 30/11/12 02:03, Iavor Diatchki wrote: Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : master http://hackage.haskell.org/trac/ghc/changeset/2ec32a8e1cb323b230b0c228dbee313647892bf4 --- commit 2ec32a8e1cb323b230b0c228dbee313647892bf4 Author: Iavor S. Diatchki diatc...@galois.com Date: Thu Nov 29 17:14:48 2012 -0800 Add :info! to GHCi. This shows all instances without filtering first. The default behavior of :info is to show only those instances of for a type, where all relevant type constructor names are in scope. This keeps down the number of instances shown to the user. In some cases, it is nice to be able to see all instances for a type. This patch implements this with the :info! command. Was there some discussion about this? The last I remember was this: http://hackage.haskell.org/trac/ghc/ticket/5998 where we decided not to implement this because it is essentially a random UI: the behaviour can't be described sensibly because it depends on which interface files GHC happens to have seen so far. There's also this: http://hackage.haskell.org/trac/ghc/ticket/3080 which looks like a duplicate (I just closed it). Cheers, Simon ___ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
Re: [commit: ghc] master: Add :info! to GHCi. This shows all instances without filtering first. (2ec32a8)
Hello Simon,
there was no discussion because I thought that this would be completely
uncontroversial since: (i) it does not change the current behavior, and
(ii) it adds new functionality which is quite useful.
Here is the use case that motivated me to implement this (described by Eric
Mertens, cc-ed on this e-mail). The example uses the `lens` package.
I know that Accessor has an Applicative instace because the operations
work. I'd like to find the instance, so I can see how it works, so I try:
Prelude Control.Applicative Control.Lens :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor {Control.Lens.Internal.runAccessor :: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal’
Weird, it doesn’t show up, so what are the instances of `Applicative`?
Prelude Control.Applicative Control.Lens :i Applicative
class Functor f = Applicative f where
pure :: a - f a
(*) :: f (a - b) - f a - f b
(*) :: f a - f b - f b
(*) :: f a - f b - f a
-- Defined in `Control.Applicative'
instance Applicative [] -- Defined in `Control.Applicative'
instance Applicative ZipList -- Defined in `Control.Applicative'
instance Monad m = Applicative (WrappedMonad m)
-- Defined in `Control.Applicative'
instance Applicative Maybe -- Defined in `Control.Applicative'
instance Applicative IO -- Defined in `Control.Applicative'
instance Applicative (Either e) -- Defined in `Control.Applicative'
instance Applicative ((-) a) -- Defined in `Control.Applicative'
instance Applicative Mutator -- Defined in `Control.Lens.Internal'
instance Applicative (Bazaar a b)
-- Defined in `Control.Lens.Internal’
It does not show up, but I'm sure that there is an instance as the
operations seem to work! It turns out that the only way to find the
instance is to not only already know that there is one and import the
appropriate module, but to also import the modules used in the context. But
if I already knew all of this I wouldn't have asked GHCi.
Prelude Control.Applicative Control.Lens import Data.Monoid
Prelude Control.Applicative Control.Lens Data.Monoid :i Accessor
newtype Accessor r a
= Control.Lens.Internal.Accessor {Control.Lens.Internal.runAccessor :: r}
-- Defined in `Control.Lens.Internal'
instance Functor (Accessor r) -- Defined in `Control.Lens.Internal'
*instance Monoid r = Applicative (Accessor r)*
-- Defined in `Control.Lens.Internal'
instance Gettable (Accessor r)
-- Defined in `Control.Lens.Internal'
In contrast, with :info! we get everything that GHCi knows about, so it
is quite easy to figure out what's going on.
-Iavor
On Fri, Nov 30, 2012 at 3:42 AM, Simon Marlow marlo...@gmail.com wrote:
On 30/11/12 02:03, Iavor Diatchki wrote:
Repository :
ssh://darcs.haskell.org//srv/**darcs/ghchttp://darcs.haskell.org//srv/darcs/ghc
On branch : master
http://hackage.haskell.org/**trac/ghc/changeset/**
2ec32a8e1cb323b230b0c228dbee31**3647892bf4http://hackage.haskell.org/trac/ghc/changeset/2ec32a8e1cb323b230b0c228dbee313647892bf4
--**--**---
commit 2ec32a8e1cb323b230b0c228dbee31**3647892bf4
Author: Iavor S. Diatchki diatc...@galois.com
Date: Thu Nov 29 17:14:48 2012 -0800
Add :info! to GHCi. This shows all instances without filtering
first.
The default behavior of :info is to show only those instances of
for a type, where all relevant type constructor names are in scope.
This keeps down the number of instances shown to the user.
In some cases, it is nice to be able to see all instances for a type.
This patch implements this with the :info! command.
Was there some discussion about this? The last I remember was this:
http://hackage.haskell.org/**trac/ghc/ticket/5998http://hackage.haskell.org/trac/ghc/ticket/5998
where we decided not to implement this because it is essentially a random
UI: the behaviour can't be described sensibly because it depends on which
interface files GHC happens to have seen so far.
There's also this:
http://hackage.haskell.org/**trac/ghc/ticket/3080http://hackage.haskell.org/trac/ghc/ticket/3080
which looks like a duplicate (I just closed it).
Cheers,
Simon
__**_
Cvs-ghc mailing list
Cvs-ghc@haskell.org
http://www.haskell.org/**mailman/listinfo/cvs-ghchttp://www.haskell.org/mailman/listinfo/cvs-ghc
___
Cvs-ghc mailing list
Cvs-ghc@haskell.org
http://www.haskell.org/mailman/listinfo/cvs-ghc
[commit: ghc] master: Add :info! to GHCi. This shows all instances without filtering first. (2ec32a8)
Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : master http://hackage.haskell.org/trac/ghc/changeset/2ec32a8e1cb323b230b0c228dbee313647892bf4 --- commit 2ec32a8e1cb323b230b0c228dbee313647892bf4 Author: Iavor S. Diatchki diatc...@galois.com Date: Thu Nov 29 17:14:48 2012 -0800 Add :info! to GHCi. This shows all instances without filtering first. The default behavior of :info is to show only those instances of for a type, where all relevant type constructor names are in scope. This keeps down the number of instances shown to the user. In some cases, it is nice to be able to see all instances for a type. This patch implements this with the :info! command. --- compiler/main/InteractiveEval.hs | 10 ++ ghc/InteractiveUI.hs | 22 -- 2 files changed, 18 insertions(+), 14 deletions(-) diff --git a/compiler/main/InteractiveEval.hs b/compiler/main/InteractiveEval.hs index 5f7d0c7..c5f35e5 100644 --- a/compiler/main/InteractiveEval.hs +++ b/compiler/main/InteractiveEval.hs @@ -890,8 +890,8 @@ moduleIsInterpreted modl = withSession $ \h - -- are in scope (qualified or otherwise). Otherwise we list a whole lot too many! -- The exact choice of which ones to show, and which to hide, is a judgement call. -- (see Trac #1581) -getInfo :: GhcMonad m = Name - m (Maybe (TyThing,Fixity,[ClsInst])) -getInfo name +getInfo :: GhcMonad m = Bool - Name - m (Maybe (TyThing,Fixity,[ClsInst])) +getInfo allInfo name = withSession $ \hsc_env - do mb_stuff - liftIO $ hscTcRnGetInfo hsc_env name case mb_stuff of @@ -900,8 +900,10 @@ getInfo name let rdr_env = ic_rn_gbl_env (hsc_IC hsc_env) return (Just (thing, fixity, filter (plausible rdr_env) ispecs)) where -plausible rdr_env ispec -- Dfun involving only names that are in ic_rn_glb_env -= all ok $ nameSetToList $ orphNamesOfType $ idType $ instanceDFunId ispec +plausible rdr_env ispec + -- Dfun involving only names that are in ic_rn_glb_env += allInfo + || all ok (nameSetToList $ orphNamesOfType $ idType $ instanceDFunId ispec) where -- A name is ok if it's in the rdr_env, -- whether qualified or not ok n | n == name = True -- The one we looked for in the first place! diff --git a/ghc/InteractiveUI.hs b/ghc/InteractiveUI.hs index 9c4a492..c0d5f19 100644 --- a/ghc/InteractiveUI.hs +++ b/ghc/InteractiveUI.hs @@ -155,7 +155,8 @@ ghciCommands = [ (forward, keepGoing forwardCmd, noCompletion), (help, keepGoing help, noCompletion), (history, keepGoing historyCmd, noCompletion), - (info, keepGoing' info,completeIdentifier), + (info, keepGoing' (info False),completeIdentifier), + (info!, keepGoing' (info True), completeIdentifier), (issafe,keepGoing' isSafeCmd, completeModule), (kind, keepGoing' (kindOfType False), completeIdentifier), (kind!, keepGoing' (kindOfType True), completeIdentifier), @@ -237,7 +238,8 @@ defFullHelpText = :edit edit last module\n ++ :etags [file] create tags file for Emacs (default: \TAGS\)\n ++ :help, :? display this list of commands\n ++ - :info [name ...] display information about the given names\n ++ + :info[!] [name ...] display information about the given names\n ++ + (!: do not filter instances)\n ++ :issafe [mod] display safe haskell information of module mod\n ++ :kind typeshow the kind of type\n ++ :load [*]module ... load module(s) and their dependents\n ++ @@ -1006,20 +1008,20 @@ help _ = do - -- :info -info :: String - InputT GHCi () -info = throwGhcException (CmdLineError syntax: ':i thing-you-want-info-about') -info s = handleSourceError GHC.printException $ do +info :: Bool - String - InputT GHCi () +info _ = throwGhcException (CmdLineError syntax: ':i thing-you-want-info-about') +info allInfo s = handleSourceError GHC.printException $ do unqual - GHC.getPrintUnqual dflags - getDynFlags -sdocs - mapM infoThing (words s) +sdocs - mapM (infoThing allInfo) (words s) mapM_ (liftIO . putStrLn . showSDocForUser dflags unqual) sdocs -infoThing :: GHC.GhcMonad m = String - m SDoc -infoThing str = do +infoThing :: GHC.GhcMonad m = Bool - String - m SDoc +infoThing allInfo str = do dflags- getDynFlags let pefas = gopt Opt_PrintExplicitForalls dflags names - GHC.parseName str -mb_stuffs - mapM GHC.getInfo names +mb_stuffs - mapM
