Re: [Haskell-cafe] One-element tuple
adam vogt vogt.adam at gmail.com writes: This preprocessor I just threw together doesn't seem to suffers from those issues http://lpaste.net/91967. This kind of approach probably might let you steal T(..) while still allowing `T (..)' to refer to whatever is the original, though I think that would require working with the messier Annotated syntax tree. wow! Adam, thank you. Even copes with multiple nested parens nested parens instance C ((a, b)) c ... == instance C ((a, b)) (OneT.OneTuple (OneT.OneTuple c)) ... AntC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
Brent Yorgey byorgey at seas.upenn.edu writes: data Oneple a = Oneple a -- (or newtype) (Oneple $ CustId 47) -- too verbose This is what the OneTuple package is for: Thank you Brent, and Ivan made the same suggestion. Apart from being more verbose (2 extra chars) than the approach I disliked as being too verbose, does OneTuple have any merit? Dan Burton danburton.email at gmail.com Fri Aug 16 03:04:14 UTC 2013 claims that T(CustId 47) is just one character off from what you actually want ... (Bare T is very likely to be used already.) But not only do I want to construct Oneples, I also want to pattern match and discriminate on their type in instances: f (T(CustId x)) = ... instance C (Oneple (CustId Int)) ... I'm sensing there must be a need (since OneTuple is claimed to be a solution for it). Would double-parens be too wild an idea?: ... ((CustId 47)) `extend` (CustName Fred, Gender Male) f ((CustId x)) = ... instance C ((CustId Int)) ... We'd have to avoid the double parens as in: ((meth obj) (double x)) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
Can you please elaborate why this inconsistency is annoying and what's the use of OneTuple? Genuine question, thanks. On Fri, Aug 16, 2013 at 5:35 AM, AntC anthony_clay...@clear.net.nz wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred)-- twople -- (CustId 47)-- oneple not! () -- nople (That is, it's annoying if you're trying to make typeclass instances for extensible/contractable tuples. Yes, I know I could use HLists.) I'm not happy with either approach I've tried: data Oneple a = Oneple a -- (or newtype) (Oneple $ CustId 47) -- too verbose type Oneple a = [a] [CustId 47] -- at least looks bracket-y What do you do? AntC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Sincerely yours, -- Daniil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
On Mon, Aug 19, 2013 at 5:40 AM, AntC anthony_clay...@clear.net.nz wrote: ... Would double-parens be too wild an idea?: ... ((CustId 47)) `extend` (CustName Fred, Gender Male) f ((CustId x)) = ... instance C ((CustId Int)) ... We'd have to avoid the double parens as in: ((meth obj) (double x)) Hi Anthony, This preprocessor I just threw together doesn't seem to suffers from those issues http://lpaste.net/91967. This kind of approach probably might let you steal T(..) while still allowing `T (..)' to refer to whatever is the original, though I think that would require working with the messier Annotated syntax tree. Regards, Adam ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
Daniel F difrumin at gmail.com writes: Can you please elaborate why this inconsistency is annoying and what's the use of OneTuple? Genuine question, Hi Daniel, the main annoyance is the verbosity (of using a data type and constructor), and that it no longer looks like a tuple. The inconsistency is because a one-element tuple is just as cromulent as a n-element, or a zero-element. (And that a one-element tuple is a distinct type from the element on its own/un-tupled.) So if I have instances (as I do) like: instance C (a, b) ... instance C () ... I can't usefully put either of these next two, because they're equiv to the third: instance C (( a )) ... instance C ( a ) ... instance C a ... -- overlaps every instance Similarly for patterns and expressions, the so-called superfluous parens are just stripped away, so equivalent to the bare term. The use of OneTuple is that it comes with all Prelude instances pre- declared (just like all other tuple constructors). I don't see that it has an advantage over declaring your own data type(?) I'd also be interested to know who is using it, and why. What I'm doing is building Type-Indexed Tuples [1] mentioned in HList [2], as an approach to extensible records [3], on the model of Trex [4] -- all of which acknowledge one-element records/rows/tuples. And then I'm using the tuples as a platform for relational algebra [5] with natural Join (and ideas from Tropashko's 'Relational Lattice' [6]). Is there anybody using OneTuple 'in anger'? AntC [1] M. Shields and E.Meijer. Type-indexed rows. In Proceedings of the 28th ACM SIGPLAN-SIGACT symposium on Principles of Programming Languages, pages 261–275. ACMPress, 2001. [2] http://hackage.haskell.org/package/HList [3] http://www.haskell.org/haskellwiki/Extensible_record [4] http://web.cecs.pdx.edu/~mpj/pubs/polyrec.html [5] http://en.wikipedia.org/wiki/Relational_algebra#Natural_join_ [6] http://vadimtropashko.wordpress.com/relational-lattice/ On Fri, Aug 16, 2013 at 5:35 AM, AntC anthony_clayden at clear.net.nz wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred) -- twople -- (CustId 47)-- oneple not! () -- nople ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
On 20 August 2013 11:07, AntC anthony_clay...@clear.net.nz wrote: Daniel F difrumin at gmail.com writes: Can you please elaborate why this inconsistency is annoying and what's the use of OneTuple? Genuine question, Hi Daniel, the main annoyance is the verbosity (of using a data type and constructor), and that it no longer looks like a tuple. The inconsistency is because a one-element tuple is just as cromulent as a n-element, or a zero-element. (And that a one-element tuple is a distinct type from the element on its own/un-tupled.) Why is it as cromulent (especially as I'm not so sure we could really consider () to be merely a zero-element tuple)? I can see what you're trying to do here, but for general usage isn't a single element tuple isomorphic to just that element (which is what newtypes are for if you need that distinction)? So if I have instances (as I do) like: instance C (a, b) ... instance C () ... I can't usefully put either of these next two, because they're equiv to the third: instance C (( a )) ... instance C ( a ) ... instance C a ... -- overlaps every instance Similarly for patterns and expressions, the so-called superfluous parens are just stripped away, so equivalent to the bare term. The use of OneTuple is that it comes with all Prelude instances pre- declared (just like all other tuple constructors). I don't see that it has an advantage over declaring your own data type(?) I'd also be interested to know who is using it, and why. As far as I'm aware, it's just a joke package, but two packages dealing with tuples seem to use it: http://packdeps.haskellers.com/reverse/OneTuple What I'm doing is building Type-Indexed Tuples [1] mentioned in HList [2], as an approach to extensible records [3], on the model of Trex [4] -- all of which acknowledge one-element records/rows/tuples. And then I'm using the tuples as a platform for relational algebra [5] with natural Join (and ideas from Tropashko's 'Relational Lattice' [6]). Is there anybody using OneTuple 'in anger'? AntC [1] M. Shields and E.Meijer. Type-indexed rows. In Proceedings of the 28th ACM SIGPLAN-SIGACT symposium on Principles of Programming Languages, pages 261–275. ACMPress, 2001. [2] http://hackage.haskell.org/package/HList [3] http://www.haskell.org/haskellwiki/Extensible_record [4] http://web.cecs.pdx.edu/~mpj/pubs/polyrec.html [5] http://en.wikipedia.org/wiki/Relational_algebra#Natural_join_ [6] http://vadimtropashko.wordpress.com/relational-lattice/ On Fri, Aug 16, 2013 at 5:35 AM, AntC anthony_clayden at clear.net.nz wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred)-- twople -- (CustId 47)-- oneple not! () -- nople ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
It seems to me that this is Identity given a different name. A bonus of using Identity is that it won't introduce any new packages to the majority of installations. On 20/08/2013 1:17 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 20 August 2013 11:07, AntC anthony_clay...@clear.net.nz wrote: Daniel F difrumin at gmail.com writes: Can you please elaborate why this inconsistency is annoying and what's the use of OneTuple? Genuine question, Hi Daniel, the main annoyance is the verbosity (of using a data type and constructor), and that it no longer looks like a tuple. The inconsistency is because a one-element tuple is just as cromulent as a n-element, or a zero-element. (And that a one-element tuple is a distinct type from the element on its own/un-tupled.) Why is it as cromulent (especially as I'm not so sure we could really consider () to be merely a zero-element tuple)? I can see what you're trying to do here, but for general usage isn't a single element tuple isomorphic to just that element (which is what newtypes are for if you need that distinction)? So if I have instances (as I do) like: instance C (a, b) ... instance C () ... I can't usefully put either of these next two, because they're equiv to the third: instance C (( a )) ... instance C ( a ) ... instance C a ... -- overlaps every instance Similarly for patterns and expressions, the so-called superfluous parens are just stripped away, so equivalent to the bare term. The use of OneTuple is that it comes with all Prelude instances pre- declared (just like all other tuple constructors). I don't see that it has an advantage over declaring your own data type(?) I'd also be interested to know who is using it, and why. As far as I'm aware, it's just a joke package, but two packages dealing with tuples seem to use it: http://packdeps.haskellers.com/reverse/OneTuple What I'm doing is building Type-Indexed Tuples [1] mentioned in HList [2], as an approach to extensible records [3], on the model of Trex [4] -- all of which acknowledge one-element records/rows/tuples. And then I'm using the tuples as a platform for relational algebra [5] with natural Join (and ideas from Tropashko's 'Relational Lattice' [6]). Is there anybody using OneTuple 'in anger'? AntC [1] M. Shields and E.Meijer. Type-indexed rows. In Proceedings of the 28th ACM SIGPLAN-SIGACT symposium on Principles of Programming Languages, pages 261–275. ACMPress, 2001. [2] http://hackage.haskell.org/package/HList [3] http://www.haskell.org/haskellwiki/Extensible_record [4] http://web.cecs.pdx.edu/~mpj/pubs/polyrec.html [5] http://en.wikipedia.org/wiki/Relational_algebra#Natural_join_ [6] http://vadimtropashko.wordpress.com/relational-lattice/ On Fri, Aug 16, 2013 at 5:35 AM, AntC anthony_clayden at clear.net.nz wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred)-- twople -- (CustId 47)-- oneple not! () -- nople ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ 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] One-element tuple
Mike Ledger eleventynine at gmail.com writes: It seems to me that this is Identity given a different name. A bonus of using Identity is that it won't introduce any new packages to the majority of installations. On 20/08/2013 1:17 PM, Ivan Lazar Miljenovic wrote: ... isn't a single element tuple isomorphic to just that element ...? Hi Mike, and Ivan, I'm not sure you're 'getting' it. A one-element tuple distinguishes at type level between a container vs contents. It's not identity/not isomorphic. Try those instances I gave. (What's worse, `Identity` is no fewer chars than `OneTuple` ;-) If your application is not working with tuples/for general usage, then no need to introduce any new packages. You won't want OneTuple's (or whatever they're called). Since I am working with tuples, I want the code to be clear where it's dealing with tuples vs the Haskell type infrastructure. Thanks Ivan for the dependencies list. No surprise that Hlist is using OneTuple == HCons a HNil. That need is exactly what I'm talking about, not a joke. Lennart's `tuple` package likewise (but no use to me because it's using positional access, not Type-Indexed). AntC So if I have instances (as I do) like: instance C (a, b) ... instance C () ... I can't usefully put either of these next two, because they're equiv to the third: instance C (( a )) ... instance C ( a ) ... instance C a ... -- overlaps every instance Similarly for patterns and expressions, the so-called superfluous parens are just stripped away, so equivalent to the bare term. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
It seems to me that this is Identity given a different name. Close. But Identity is declared using newtype (just like monad transformers), whereas OneTuple is declared with data (like the other tuples). This may or may not matter, depending on your use case. On 20/08/2013 1:17 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 20 August 2013 11:07, AntC anthony_clay...@clear.net.nz wrote: Daniel F difrumin at gmail.com writes: Can you please elaborate why this inconsistency is annoying and what's the use of OneTuple? Genuine question, Hi Daniel, the main annoyance is the verbosity (of using a data type and constructor), and that it no longer looks like a tuple. The inconsistency is because a one-element tuple is just as cromulent as a n-element, or a zero-element. (And that a one-element tuple is a distinct type from the element on its own/un-tupled.) Why is it as cromulent (especially as I'm not so sure we could really consider () to be merely a zero-element tuple)? I can see what you're trying to do here, but for general usage isn't a single element tuple isomorphic to just that element (which is what newtypes are for if you need that distinction)? So if I have instances (as I do) like: instance C (a, b) ... instance C () ... I can't usefully put either of these next two, because they're equiv to the third: instance C (( a )) ... instance C ( a ) ... instance C a ... -- overlaps every instance Similarly for patterns and expressions, the so-called superfluous parens are just stripped away, so equivalent to the bare term. The use of OneTuple is that it comes with all Prelude instances pre- declared (just like all other tuple constructors). I don't see that it has an advantage over declaring your own data type(?) I'd also be interested to know who is using it, and why. As far as I'm aware, it's just a joke package, but two packages dealing with tuples seem to use it: http://packdeps.haskellers.com/reverse/OneTuple What I'm doing is building Type-Indexed Tuples [1] mentioned in HList [2], as an approach to extensible records [3], on the model of Trex [4] -- all of which acknowledge one-element records/rows/tuples. And then I'm using the tuples as a platform for relational algebra [5] with natural Join (and ideas from Tropashko's 'Relational Lattice' [6]). Is there anybody using OneTuple 'in anger'? AntC [1] M. Shields and E.Meijer. Type-indexed rows. In Proceedings of the 28th ACM SIGPLAN-SIGACT symposium on Principles of Programming Languages, pages 261–275. ACMPress, 2001. [2] http://hackage.haskell.org/package/HList [3] http://www.haskell.org/haskellwiki/Extensible_record [4] http://web.cecs.pdx.edu/~mpj/pubs/polyrec.html [5] http://en.wikipedia.org/wiki/Relational_algebra#Natural_join_ [6] http://vadimtropashko.wordpress.com/relational-lattice/ On Fri, Aug 16, 2013 at 5:35 AM, AntC anthony_clayden at clear.net.nz wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred)-- twople -- (CustId 47)-- oneple not! () -- nople ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ 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 -- Chris Wong, fixpoint conjurer e: lambda.fa...@gmail.com w: http://lfairy.github.io/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
On Fri, Aug 16, 2013 at 01:35:22AM +, AntC wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred)-- twople -- (CustId 47)-- oneple not! () -- nople (That is, it's annoying if you're trying to make typeclass instances for extensible/contractable tuples. Yes, I know I could use HLists.) I'm not happy with either approach I've tried: data Oneple a = Oneple a -- (or newtype) (Oneple $ CustId 47) -- too verbose type Oneple a = [a] [CustId 47] -- at least looks bracket-y What do you do? This is what the OneTuple package is for: http://hackage.haskell.org/package/OneTuple -Brent ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
On 16 August 2013 11:35, AntC anthony_clay...@clear.net.nz wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred)-- twople -- (CustId 47)-- oneple not! () -- nople (That is, it's annoying if you're trying to make typeclass instances for extensible/contractable tuples. Yes, I know I could use HLists.) I'm not happy with either approach I've tried: data Oneple a = Oneple a -- (or newtype) (Oneple $ CustId 47) -- too verbose type Oneple a = [a] [CustId 47] -- at least looks bracket-y What do you do? http://hackage.haskell.org/package/OneTuple :p If you really wanted some form of parentheses you could possibly use quasiquoting for it... AntC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-element tuple
For the consistency you want, `data Oneple a = T a` is the best you can do in Haskell. T(CustId 47) is just one character off from what you actually want to write: (Cust 47). And I presume you want the extra bottom that comes with this, as opposed to just treating values as their own one-tuples. I imagine you could write some fancy hack that uses the type system to automatically promote values to Oneples of the given value when an expected: Oneple Foo, actual: Foo error occurs. But this would not be very useful in general. An uglier option: type Oneple a = (a, ()) -- Dan Burton On Thu, Aug 15, 2013 at 7:05 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 16 August 2013 11:35, AntC anthony_clay...@clear.net.nz wrote: There's an annoying inconsistency: (CustId 47, CustName Fred, Gender Male) -- threeple (CustId 47, CustName Fred)-- twople -- (CustId 47)-- oneple not! () -- nople (That is, it's annoying if you're trying to make typeclass instances for extensible/contractable tuples. Yes, I know I could use HLists.) I'm not happy with either approach I've tried: data Oneple a = Oneple a -- (or newtype) (Oneple $ CustId 47) -- too verbose type Oneple a = [a] [CustId 47] -- at least looks bracket-y What do you do? http://hackage.haskell.org/package/OneTuple :p If you really wanted some form of parentheses you could possibly use quasiquoting for it... AntC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ 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
