Is generic information dumpable?

Magicloud Magiclouds

3 Nov 2011 3 Nov '11

12:26 p.m.

Hi, I am learning the new generic feature of ghc. I'd have to say, it is harder than template to enter. When I started to learn template, ghc -ddump-slices really helped. So I wonder if I could get the representation generated when deriving Generic. I think that would be a great help. -- 竹密岂妨流水过山高哪阻野云飞

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José Pedro Magalhães

3 Nov 3 Nov

12:30 p.m.

"-ddump-deriv" will print (most of) it. Cheers, Pedro On Thu, Nov 3, 2011 at 16:26, Magicloud Magiclouds < magicloud.magiclouds@gmail.com> wrote:

...

Hi, I am learning the new generic feature of ghc. I'd have to say, it is harder than template to enter. When I started to learn template, ghc -ddump-slices really helped. So I wonder if I could get the representation generated when deriving Generic. I think that would be a great help. -- 竹密岂妨流水过山高哪阻野云飞

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Bas van Dijk

7:26 p.m.

2011/11/3 José Pedro Magalhães :

...

"-ddump-deriv" will print (most of) it.

But it doesn't print the most useful piece of information: the definition of Rep. It would be great if this could be added. Currently when I have a type that I want to know the Rep of, say: data Foo = Bar Int | Boo {hello :: String} deriving Generic I just convert it to a Rep and show it: err = show $ from $ Boo "World" However Reps don't have Show instances so GHC complains: No instance for (Show (D1 D1Foo ( C1 C1_0Foo (S1 NoSelector (Rec0 Int)) :+: C1 C1_1Foo (S1 S1_1_0Foo (Rec0 String)) ) x0 ) ) arising from a use of `show' And there you go. This is the only time when I'm happy to see an error message :-) Bas

José Pedro Magalhães

7:33 p.m.

Hi, 2011/11/3 Bas van Dijk

...

2011/11/3 José Pedro Magalhães :

...
"-ddump-deriv" will print (most of) it.

But it doesn't print the most useful piece of information: the definition of Rep.

Yes... I am aware of this.

...

It would be great if this could be added.

I'll do it. Cheers, Pedro

Bas van Dijk

8:01 p.m.

2011/11/4 José Pedro Magalhães :

...

Hi,

2011/11/3 Bas van Dijk

...
2011/11/3 José Pedro Magalhães :

...
"-ddump-deriv" will print (most of) it.

But it doesn't print the most useful piece of information: the definition of Rep.

Yes... I am aware of this.

...
It would be great if this could be added.

I'll do it.

Cheers, Pedro

Great, thanks!

José Pedro Magalhães

4 Nov 4 Nov

6:25 a.m.

Hi, Now, for the following datatype: data X a = X { myX :: a } deriving Generic You get the following -ddump-deriv output: ==================== Derived instances ==================== Derived instances: instance GHC.Generics.Generic (Temp.X a_adY) where GHC.Generics.from (Temp.X g1_aeG) = GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1_aeG))) GHC.Generics.to (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1_aeH)))) = Temp.X g1_aeH instance GHC.Generics.Datatype Temp.D1X where GHC.Generics.datatypeName _ = "X" GHC.Generics.moduleName _ = "Temp" instance GHC.Generics.Constructor Temp.C1_0X where GHC.Generics.conName _ = "X" GHC.Generics.conIsRecord _ = GHC.Types.True instance GHC.Generics.Selector Temp.S1_0_0X where GHC.Generics.selName _ = "myX" Generic representation: Generated datatypes for meta-information: Temp.D1X Temp.C1_0X Temp.S1_0_0X Representation types: Temp.Rep_X = GHC.Generics.D1 Temp.D1X (GHC.Generics.C1 Temp.C1_0X (GHC.Generics.S1 Temp.S1_0_0X (GHC.Generics.Par0 a_adY))) Still not perfect, in that the representation type should really appear as a type instance inside the Generic instance, but at least all the important information is printed. Cheers, Pedro 2011/11/3 Bas van Dijk

...

2011/11/3 José Pedro Magalhães :

...
"-ddump-deriv" will print (most of) it.

But it doesn't print the most useful piece of information: the definition of Rep.

It would be great if this could be added.

Currently when I have a type that I want to know the Rep of, say:

data Foo = Bar Int | Boo {hello :: String} deriving Generic

I just convert it to a Rep and show it:

err = show $ from $ Boo "World"

However Reps don't have Show instances so GHC complains:

No instance for (Show (D1 D1Foo ( C1 C1_0Foo (S1 NoSelector (Rec0 Int)) :+: C1 C1_1Foo (S1 S1_1_0Foo (Rec0 String)) ) x0 ) ) arising from a use of `show'

And there you go. This is the only time when I'm happy to see an error message :-)

Bas

Bas van Dijk

6:31 a.m.

Thanks José! Will this make it into ghc-7.4? Bas 2011/11/4 José Pedro Magalhães :

...

Hi, Now, for the following datatype: data X a = X { myX :: a } deriving Generic You get the following -ddump-deriv output: ==================== Derived instances ==================== Derived instances: instance GHC.Generics.Generic (Temp.X a_adY) where GHC.Generics.from (Temp.X g1_aeG) = GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1_aeG))) GHC.Generics.to (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1_aeH)))) = Temp.X g1_aeH

instance GHC.Generics.Datatype Temp.D1X where GHC.Generics.datatypeName _ = "X" GHC.Generics.moduleName _ = "Temp"

instance GHC.Generics.Constructor Temp.C1_0X where GHC.Generics.conName _ = "X" GHC.Generics.conIsRecord _ = GHC.Types.True

instance GHC.Generics.Selector Temp.S1_0_0X where GHC.Generics.selName _ = "myX"

Generic representation:

Generated datatypes for meta-information: Temp.D1X Temp.C1_0X Temp.S1_0_0X

Representation types: Temp.Rep_X = GHC.Generics.D1 Temp.D1X (GHC.Generics.C1 Temp.C1_0X (GHC.Generics.S1 Temp.S1_0_0X (GHC.Generics.Par0 a_adY))) Still not perfect, in that the representation type should really appear as a type instance inside the Generic instance, but at least all the important information is printed.

Cheers, Pedro

2011/11/3 Bas van Dijk

...
2011/11/3 José Pedro Magalhães :

...
"-ddump-deriv" will print (most of) it.

But it doesn't print the most useful piece of information: the definition of Rep.

It would be great if this could be added.

Currently when I have a type that I want to know the Rep of, say:

data Foo = Bar Int | Boo {hello :: String} deriving Generic

I just convert it to a Rep and show it:

err = show $ from $ Boo "World"

However Reps don't have Show instances so GHC complains:

No instance for (Show (D1 D1Foo ( C1 C1_0Foo (S1 NoSelector (Rec0 Int)) :+: C1 C1_1Foo (S1 S1_1_0Foo (Rec0 String)) ) x0 ) ) arising from a use of `show'

And there you go. This is the only time when I'm happy to see an error message :-)

Bas

José Pedro Magalhães

6:36 a.m.

2011/11/4 Bas van Dijk

...

Thanks José!

Will this make it into ghc-7.4?

Yes, I think so. Cheers, Pedro

...

Bas

2011/11/4 José Pedro Magalhães :

...
Hi, Now, for the following datatype: data X a = X { myX :: a } deriving Generic You get the following -ddump-deriv output: ==================== Derived instances ==================== Derived instances: instance GHC.Generics.Generic (Temp.X a_adY) where GHC.Generics.from (Temp.X g1_aeG) = GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1_aeG))) GHC.Generics.to (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1_aeH)))) = Temp.X g1_aeH

instance GHC.Generics.Datatype Temp.D1X where GHC.Generics.datatypeName _ = "X" GHC.Generics.moduleName _ = "Temp"

instance GHC.Generics.Constructor Temp.C1_0X where GHC.Generics.conName _ = "X" GHC.Generics.conIsRecord _ = GHC.Types.True

instance GHC.Generics.Selector Temp.S1_0_0X where GHC.Generics.selName _ = "myX"

Generic representation:

Generated datatypes for meta-information: Temp.D1X Temp.C1_0X Temp.S1_0_0X

Representation types: Temp.Rep_X = GHC.Generics.D1 Temp.D1X (GHC.Generics.C1 Temp.C1_0X (GHC.Generics.S1 Temp.S1_0_0X (GHC.Generics.Par0 a_adY))) Still not perfect, in that the representation type should really appear as a type instance inside the Generic instance, but at least all the important information is printed.

Cheers, Pedro

2011/11/3 Bas van Dijk

...
2011/11/3 José Pedro Magalhães :

...
"-ddump-deriv" will print (most of) it.

But it doesn't print the most useful piece of information: the definition of Rep.

It would be great if this could be added.

Currently when I have a type that I want to know the Rep of, say:

data Foo = Bar Int | Boo {hello :: String} deriving Generic

I just convert it to a Rep and show it:

err = show $ from $ Boo "World"

However Reps don't have Show instances so GHC complains:

No instance for (Show (D1 D1Foo ( C1 C1_0Foo (S1 NoSelector (Rec0 Int)) :+: C1 C1_1Foo (S1 S1_1_0Foo (Rec0 String)) ) x0 ) ) arising from a use of `show'

And there you go. This is the only time when I'm happy to see an error message :-)

Bas

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Bas van Dijk
José Pedro Magalhães
Magicloud Magiclouds

Is generic information dumpable?

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