Re: [Haskell-cafe] Infix tuple comma query (,)
On Mon, Apr 6, 2009 at 8:53 AM, Paul Keir wrote: > module Main where > > > > data (:%^&) a b = a :%^& b deriving (Show) > > > > main = do > > print $ 18 :%^& (Just 99) > > print $ (,) 9 10 > > print $ 9 , 10 > > > > The last line in the code above causes a compile error. > > Why does infix use of the comma (tuple constructor?) function fail without > brackets? > > > > Thanks, > > Paul > When I want a lighter syntax for pairs (when doing a long list of them, e.g.), I often define (&) :: a -> b -> (a,b) a & b = (a,b) and then you can indeed write print $ 1 & 2 (assuming you get precedence right). Alex ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Infix tuple comma query (,)
The prefix notation for > \a b c -> (a,b,c) is (,,) Without the parentheses, it's not immediately clear whether > foo $ a,b means > foo (a,b) or > foo (\c -> (a,b,c)) or some other, bigger tuple size. Anyways, it's just syntax :) -- ryan On Mon, Apr 6, 2009 at 9:08 AM, Daniel Fischer wrote: > Am Montag 06 April 2009 17:53:24 schrieb Paul Keir: >> module Main where >> >> >> >> data (:%^&) a b = a :%^& b deriving (Show) >> >> >> >> main = do >> >> print $ 18 :%^& (Just 99) >> >> print $ (,) 9 10 >> >> print $ 9 , 10 >> >> >> >> The last line in the code above causes a compile error. >> >> Why does infix use of the comma (tuple constructor?) function fail >> without brackets? >> > > Tuples are special baked-in syntax. The parentheses are part of the tuple > constructor(s). > It may be confusing you that you can use it prefix as well as "aroundfix". > >> >> >> Thanks, >> >> Paul > > ___ > 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] Infix tuple comma query (,)
Am Montag 06 April 2009 17:53:24 schrieb Paul Keir: > module Main where > > > > data (:%^&) a b = a :%^& bderiving (Show) > > > > main = do > > print $ 18 :%^& (Just 99) > > print $ (,) 9 10 > > print $ 9 , 10 > > > > The last line in the code above causes a compile error. > > Why does infix use of the comma (tuple constructor?) function fail > without brackets? > Tuples are special baked-in syntax. The parentheses are part of the tuple constructor(s). It may be confusing you that you can use it prefix as well as "aroundfix". > > > Thanks, > > Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Infix tuple comma query (,)
module Main where data (:%^&) a b = a :%^& bderiving (Show) main = do print $ 18 :%^& (Just 99) print $ (,) 9 10 print $ 9 , 10 The last line in the code above causes a compile error. Why does infix use of the comma (tuple constructor?) function fail without brackets? Thanks, Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
