Or better numDigits = length . show It's probably even faster. 2009/8/22 Eugene Kirpichov <ekirpic...@gmail.com>: > Use 'round' instead of 'truncate'. > > Prelude> let numDigits = (+1) . round . logBase 10 . fromIntegral > Prelude> map (numDigits . (10^)) [0..9] > [1,2,3,4,5,6,7,8,9,10] > > 2009/8/22 Roberto López <plasterm...@hotmail.com>: >> Ok. I wonder if someone could help me with this problem... >> >> I want to calculate the number of digits of a positive integer. I was >> thinking of ... >> >> numDigits n = truncate (logBase 10 n) + 1 >> >> But (logBase 10 1000) = 2.9999999999999996 so numDigits 1000 = 2. >> >> Maybe adding a small amount >> >> numDigits n = truncate ((logBase 10 n) + 0.0000000000000005) + 1 >> >> Prelude> numDigits 100 >> 3 >> Prelude> numDigits 1000 >> 4 >> Prelude> numDigits 10000 >> 5 >> Prelude> numDigits 10000 >> 5 >> Prelude> numDigits 100000 >> 6 >> Prelude> numDigits 1000000 >> 7 >> Prelude> numDigits 10000000 >> 8 >> Prelude> numDigits 100000000 >> 9 >> Prelude> numDigits 1000000000 >> 9 <---- This is wrong!!!! >> Prelude> numDigits 10000000000 >> 11 >> >> Is there a reliable way to calculate the number of digits by means of >> logBase? >> >> >> Regards! >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe@haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> > > > > -- > Eugene Kirpichov > Web IR developer, market.yandex.ru >
-- Eugene Kirpichov Web IR developer, market.yandex.ru _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
