[Haskell-cafe] Number formatting
Hello, is there a function which will format a number with separators, something that will turn 14509.8674 into 14,509.86? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Number formatting
Günther Schmidt wrote: is there a function which will format a number with separators, something that will turn 14509.8674 into 14,509.86? There's a small function to do it here: http://bluebones.net/2007/02/formatting-decimals-in-haskell/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Number formatting
Hello All Alternatively, less dependencies and a bit less golf (but not much testing...): Best wishes Stephen import Data.List import Numeric formatDecimal :: RealFloat a = a - String formatDecimal d = let s = showFFloat (Just 2) d (a,b) = break (=='.') s in (intersperseN 3 ',' a) ++ b intersperseN :: Int - a - [a] - [a] intersperseN n a = snd . para phi (1,[]) where phi x ((_:_), (i,acc)) | i == n = (1, a : x : acc) phi x (_, (i,acc)) = (i+1, x : acc) -- paramorphism (generalizes fold) para :: (a - ([a], b) - b) - b - [a] - b para phi b = step where step [] = b step (x:xs) = phi x (xs, step xs) On 8 February 2010 11:17, Anton van Straaten an...@appsolutions.com wrote: There's a small function to do it here: http://bluebones.net/2007/02/formatting-decimals-in-haskell/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Number formatting
Hi Günther Ahem... *FormatDecimal formatDecimal (888.005) ,888.01 I'll post a revision shortly (that handles negatives as well) ... On 8 February 2010 13:09, Stephen Tetley stephen.tet...@gmail.com wrote: Hello All Alternatively, less dependencies and a bit less golf (but not much testing...): ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Number formatting
Hello I'd overlooked that the left-to-right behaviour of the paramorphism when I needed to go right-to-left, here's a version with a rather horrible right fold (different seeds for the counter, ho-hum, but easily testable): import Data.List import Numeric formatDecimal :: RealFloat a = a - String formatDecimal d | d 0 = '-' : fmt (negate d) | otherwise = fmt d where fmt x = let s = showFFloat (Just 2) x (a,b) = break (=='.') s in (intersperseN_rl 3 ',' a) ++ b intersperseN_rl :: Int - a - [a] - [a] intersperseN_rl n sep xs = snd $ foldr phi (0,[]) xs where phi a (i,acc) | i == n= (1, a : sep : acc) | otherwise = (i+1, a : acc) test01 :: IO () test01 = mapM_ (print . (intersperseN_rl 3 ',')) $ inits abcdefghijklmno *FormatDecimal test01 a ab abc a,bcd ab,cde abc,def a,bcd,efg ab,cde,fgh abc,def,ghi a,bcd,efg,hij ab,cde,fgh,ijk abc,def,ghi,jkl a,bcd,efg,hij,klm ab,cde,fgh,ijk,lmn abc,def,ghi,jkl,mno On 8 February 2010 13:40, Stephen Tetley stephen.tet...@gmail.com wrote: Ahem... *FormatDecimal formatDecimal (888.005) ,888.01 I'll post a revision shortly (that handles negatives as well) ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
