Re: [Haskell-cafe] Showing the 1 element tuple
On Fri, Dec 22, 2006 at 11:13:50AM -0800, Dan Weston wrote: > More generally, is there an operator version of dotted pair notation > (gasp, did I just lisp?) that works like: > > data Tuple a b = () | Tuple a b > > ()== () > ( ) 1 == Tuple 1 () > (2,'a',"hello") == Tuple 2 (Tuple 'a' (Tuple "hello" ())) > > And is there anyway in Haskell to restrict the type definition above to > require that b be a type that can be constructed (possibly recursively) > with only () or Tuple, so the user doesn't do something stupid like > Tuple 1 'a', which is not a valid dotted pair? HList seems similar to what you are going for: http://homepages.cwi.nl/~ralf/HList/ John -- John Meacham - ⑆repetae.net⑆john⑈ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
More generally, is there an operator version of dotted pair notation (gasp, did I just lisp?) that works like: data Tuple a b = () | Tuple a b ()== () ( ) 1 == Tuple 1 () (2,'a',"hello") == Tuple 2 (Tuple 'a' (Tuple "hello" ())) And is there anyway in Haskell to restrict the type definition above to require that b be a type that can be constructed (possibly recursively) with only () or Tuple, so the user doesn't do something stupid like Tuple 1 'a', which is not a valid dotted pair? Dan John Meacham wrote: have it be ( ) 1 with a space between the parens to denote that it is a single tuple rather than a nullary one. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
have it be ( ) 1 with a space between the parens to denote that it is a single tuple rather than a nullary one. John -- John Meacham - ⑆repetae.net⑆john⑈ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
On Tue, 19 Dec 2006, Neil Mitchell wrote: > () -- 0 element tuple > (,) a b -- 2 element tuple > (,,) a b c -- 3 element tuple The problem is that the separator approach (comma) doesn't scale well: http://haskell.org/haskellwiki/Terminator_vs._separator ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
> A weird question, what does the 1 element tuple look like? there is one in Control.Monad.Identity: Identity 1 i miss the short version newtype Id x = x writing (1,) is not that well defined; how do you want to use its constructor alone? writing (1;) may be the solution, i think. (;) could be the constructor. does anyone know, how ";" could cause any problems? if i am not mistaken, (do return 1 ; return 2;) should be the same like ((do return 1 ; return 2);). - marc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
Hi Python uses the syntax (foo,) to denote a singleton tuple (that is an extra comma at the end); quoting the python tutorial "Ugly, but effective". Yes, I thought of that, the issue is: (a,b) is considered syntactic sugar for (,) a b (a,) is syntactic sugar for... And the place I'm displaying this is definately after desugaring! Could tuples be implemented as an HList? singleton = (`hCons` hNil) Not in Yhc, no higher rank types :) Also tuples are really really common, every class function has quite a few floating around - HList is just too much overhead (I think). Tuples represent dimensionality therefore a 1-element tuple is just a 1-dimensional value ie the value itself hence a == (a) == ((a)) == (((a))) Tuples are a box you can put things in, in Haskell: data Tuple a = Tuple a Tuple (Tuple 1) /= 1 (either at runtime, at type time, or any other time) Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
On Tue, Dec 19, 2006 at 11:35:49PM -, Brian Hulley wrote: > Tuples represent dimensionality therefore a 1-element tuple is just a > 1-dimensional value ie the value itself hence a == (a) == ((a)) == (((a))) That is true in a strict language, and for unboxed (unlifted) types, but in haskell tuples are lifted types -- (a) contains _|_ and (_|_), while a only contains _|_. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
Neil Mitchell wrote: Hi, A weird question, what does the 1 element tuple look like? () -- 0 element tuple (,) a b -- 2 element tuple (,,) a b c -- 3 element tuple () a - meaningless (a) - a in brackets GHC has the 1 element unboxed tuple, (# a #), and all the other sizes unboxed as well, but how would you visually represent the 1 element boxed tuple? Tuples represent dimensionality therefore a 1-element tuple is just a 1-dimensional value ie the value itself hence a == (a) == ((a)) == (((a))) == ... Brian. -- http://www.metamilk.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
Neil, On Tue, Dec 19, 2006 at 10:41:56PM +, Neil Mitchell wrote: A weird question, what does the 1 element tuple look like? Could tuples be implemented as an HList? singleton = (`hCons` hNil) -Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
On Tue, Dec 19, 2006 at 10:41:56PM +, Neil Mitchell wrote: Hi, A weird question, what does the 1 element tuple look like? () -- 0 element tuple (,) a b -- 2 element tuple (,,) a b c -- 3 element tuple () a - meaningless (a) - a in brackets GHC has the 1 element unboxed tuple, (# a #), and all the other sizes unboxed as well, but how would you visually represent the 1 element boxed tuple? As it happens, Yhc _does_ have the 1 element tuple, you just can't use it from normal programs, its only created by desugarings of class instances. I'd quite like to change this, and I also need to render the 1 element tuple in some way, so wondered if anyone had any good ideas (or if there is even some sort of convention) I currently use ()1, but don't like that as it doesn't follow Haskell rules - the () and 1 would be separate lexemes. My other thought is (?), where ? is something appropriate - but all the appropriate things I can think of would either not be a lexeme (i.e. 1), having an existing meaning (i.e. . | etc) or seem wrong. Thoughts? Python seems to use (1,) which seems reasonably clear. -- Dennis Griffith, [EMAIL PROTECTED] Treasurer ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing the 1 element tuple
On Tue, Dec 19, 2006 at 10:41:56PM +, Neil Mitchell wrote: > A weird question, what does the 1 element tuple look like? > > () -- 0 element tuple > (,) a b -- 2 element tuple > (,,) a b c -- 3 element tuple > > () a - meaningless > (a) - a in brackets ... > Thoughts? Python uses the syntax (foo,) to denote a singleton tuple (that is an extra comma at the end); quoting the python tutorial "Ugly, but effective". ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Showing the 1 element tuple
Hi, A weird question, what does the 1 element tuple look like? () -- 0 element tuple (,) a b -- 2 element tuple (,,) a b c -- 3 element tuple () a - meaningless (a) - a in brackets GHC has the 1 element unboxed tuple, (# a #), and all the other sizes unboxed as well, but how would you visually represent the 1 element boxed tuple? As it happens, Yhc _does_ have the 1 element tuple, you just can't use it from normal programs, its only created by desugarings of class instances. I'd quite like to change this, and I also need to render the 1 element tuple in some way, so wondered if anyone had any good ideas (or if there is even some sort of convention) I currently use ()1, but don't like that as it doesn't follow Haskell rules - the () and 1 would be separate lexemes. My other thought is (?), where ? is something appropriate - but all the appropriate things I can think of would either not be a lexeme (i.e. 1), having an existing meaning (i.e. . | etc) or seem wrong. Thoughts? Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
