Re: [Haskell-cafe] Probably type checker error.
Not just a proposal any more. :-) GHC 7.0 does not generalize local let bindings in some situations. See here for information: http://hackage.haskell.org/trac/ghc/blog/LetGeneralisationInGhc7 There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Probably type checker error.
Yeah, seems to work too. Отправлено с iPhone Jun 20, 2011, в 10:55, Corey O'Connor coreyocon...@gmail.com написал(а): Not just a proposal any more. :-) GHC 7.0 does not generalize local let bindings in some situations. See here for information: http://hackage.haskell.org/trac/ghc/blog/LetGeneralisationInGhc7 There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Probably type checker error.
The fact is that (Num a) context works and (ToWires a, Num a) context doesn't. At least in 6.12.1. This still looks to me like a bug. 2011/6/19 Miguel Mitrofanov miguelim...@yandex.ru: Seems like let-generalization is at work here. Types of all values in the where section are inferred basically as if they are declared at the top level. Therefore, inheritance fails without NoMonomorphismRestriction. There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Probably type checker error.
GHC 6.12 introduces MonoLocalBinds, which disables polymorphic values in let statements. Your original code works for me if I use -XNoMonoLocalBinds -XNoMonomorphismRestriction. On Mon, Jun 20, 2011 at 9:02 AM, Serguey Zefirov sergu...@gmail.com wrote: The fact is that (Num a) context works and (ToWires a, Num a) context doesn't. At least in 6.12.1. This still looks to me like a bug. 2011/6/19 Miguel Mitrofanov miguelim...@yandex.ru: Seems like let-generalization is at work here. Types of all values in the where section are inferred basically as if they are declared at the top level. Therefore, inheritance fails without NoMonomorphismRestriction. There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Dave Menendez d...@zednenem.com http://www.eyrie.org/~zednenem/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Probably type checker error.
Thank you very much. I'll try that too. 2011/6/20 David Menendez d...@zednenem.com: GHC 6.12 introduces MonoLocalBinds, which disables polymorphic values in let statements. Your original code works for me if I use -XNoMonoLocalBinds -XNoMonomorphismRestriction. On Mon, Jun 20, 2011 at 9:02 AM, Serguey Zefirov sergu...@gmail.com wrote: The fact is that (Num a) context works and (ToWires a, Num a) context doesn't. At least in 6.12.1. This still looks to me like a bug. 2011/6/19 Miguel Mitrofanov miguelim...@yandex.ru: Seems like let-generalization is at work here. Types of all values in the where section are inferred basically as if they are declared at the top level. Therefore, inheritance fails without NoMonomorphismRestriction. There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Dave Menendez d...@zednenem.com http://www.eyrie.org/~zednenem/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Probably type checker error.
Defaulting. Inferred type of r is still polymorphic – r :: E ins outs – but type of x, nextSum and currentSum is defaulted to Integer. Try adding default () to your program, and you'll see the same error again. Or, if you enable NoMonomorphismRestriction (or MonoLocalBinds – I didn't know it works in 6.12 also), you'll see that the type of nextSum etc. is derived as Num a = a. On 20 Jun 2011, at 17:02, Serguey Zefirov wrote: The fact is that (Num a) context works and (ToWires a, Num a) context doesn't. At least in 6.12.1. This still looks to me like a bug. 2011/6/19 Miguel Mitrofanov miguelim...@yandex.ru: Seems like let-generalization is at work here. Types of all values in the where section are inferred basically as if they are declared at the top level. Therefore, inheritance fails without NoMonomorphismRestriction. There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Probably type checker error.
Cool. It works. Thank you very much! 2011/6/19 Miguel Mitrofanov miguelim...@yandex.ru: Seems like let-generalization is at work here. Types of all values in the where section are inferred basically as if they are declared at the top level. Therefore, inheritance fails without NoMonomorphismRestriction. There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Probably type checker error.
Seems like let-generalization is at work here. Types of all values in the where section are inferred basically as if they are declared at the top level. Therefore, inheritance fails without NoMonomorphismRestriction. There is a proposal (from Big Simon) to remove let-generalization: http://research.microsoft.com/en-us/um/people/simonpj/papers/constraints/let-gen.pdf On 19 Jun 2011, at 18:26, Serguey Zefirov wrote: Right now I write a quite heavy transformation of Haskell source code and found some strange behaviour of typechecker. Some prerequisites: -- dummy class. My own class is much bigger, but I -- could reproduce that behaviour with that class. class ToWires a -- a type with phantom type arguments. data E ins outs = E -- a function that relates E and its inputs. projectInsType :: E ins outs - ins projectInsType = error projectInsType gets evaluated. -- register function. register :: a - a - a register def a = def -- a simple addition. add2 :: (ToWires a, Num a) = (a,a) - a add2 (a,b) = a+b First I have a function: func :: (ToWires a, Num a) = Maybe a - a func mbA = currentSum where x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum It typechecks and works just fine after some transformation. The transformation I work on transform code into something like that: func_E :: (ToWires a, Num a) = E (Maybe a) a func_E = r where r = E -- here we relate mbA and r. mbA = projectInsType r x = case mbA of Just a - a Nothing - 0 nextSum = add2 (x,currentSum) currentSum = register 0 nextSum Note the absence of input of func in transformed func_E. I relate mbA with it's proper type using binding mbA = projectInsType r. Then suddently ghc loses all of the context associated with mbA. And find type error at the calling of add2. If I drop ToWires from contexts of func_E and add2 types, all works fine. If I change add2 to simple addition (x + currentSum), all works fine. Full source code is in attachment. I found it using ghc 6.12.1. I asked colleagues, they told me that the same error manifests itself in ghc 7.0.3. Should I fill a bug report or maybe I misunderstood something? a.hs___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
