Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Although this isn't a very "general approach", I just submitted a patch to GHC (not yet merged) with a gmp binding to mpz_sizeinbase, which would allow for very quick computation of number of digits in any base. On Sat, Aug 29, 2009 at 9:12 PM, Edward Kmett wrote: > I have a version of this inside

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

I have a version of this inside of the monoid library buried in the Data.Ring.Semi.BitSet module: http://comonad.com/haskell/monoids/dist/doc/html/monoids/src/Data-Ring-Semi-BitSet.html#hwm To do any bette

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Uwe Hollerbach wrote: > Here's my version... maybe not as elegant as some, but it seems to > work. For base 2 (or 2^k), it's probably possible to make this even > more efficient by just walking along the integer as stored in memory, > but that difference probably won't show up until at least tens o

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Here's my version... maybe not as elegant as some, but it seems to work. For base 2 (or 2^k), it's probably possible to make this even more efficient by just walking along the integer as stored in memory, but that difference probably won't show up until at least tens of thousands of digits. Uwe i

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

2009/8/26 Lennart Augustsson : > Try 10^1000 Cheat :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Am Mittwoch 26 August 2009 06:29:47 schrieb George Pollard: > You could also fudge the input: > > {-# LANGUAGE NoMonomorphismRestriction #-} > > log10 = floor . logBase 10 . (0.5+) . fromIntegral > > numDigits n | n < 0 = 1 + numDigits (-n) > numDigits 0 = 1 > numDigits n = 1 + log1

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

You could also fudge the input: {-# LANGUAGE NoMonomorphismRestriction #-} log10 = floor . logBase 10 . (0.5+) . fromIntegral numDigits n | n < 0 = 1 + numDigits (-n) numDigits 0 = 1 numDigits n = 1 + log10 n -- checked [0..10^8], finding a counter-example is left as an exercise

Re[2]: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Hello Henning, Tuesday, August 25, 2009, 6:11:00 PM, you wrote: >> digits = iterate (`div` 10) >>> takeWhile (>0) >>> length > This needs quadratic time with respect to the number of digits, doesn't > it? why? i think that `show` uses pretty the same way to build list of digits, so we just omi

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

On Sat, 22 Aug 2009, Bulat Ziganshin wrote: Hello Roberto, Saturday, August 22, 2009, 9:19:26 PM, you wrote: I want to calculate the number of digits of a positive integer. I was fastest way digits = iterate (`div` 10) >>> takeWhile (>0) >>> length This needs quadratic time with respect

Re[2]: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Hello José, Saturday, August 22, 2009, 10:36:33 PM, you wrote: ghci doesn't optimize > It looks like length . show is faster -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-C

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

It looks like length . show is faster Prelude Control.Arrow> let numDigits n = length $ show n Prelude Control.Arrow> let digits = iterate (`div` 10) >>> takeWhile (>0) >>> length Prelude Control.Arrow> let n=2^100 Prelude Control.Arrow> :set +s Prelude Control.Arrow> numDigits n 301030 (0.39

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Hello Roberto, Saturday, August 22, 2009, 9:19:26 PM, you wrote: > I want to calculate the number of digits of a positive integer. I was fastest way digits = iterate (`div` 10) >>> takeWhile (>0) >>> length -- Best regards, Bulatmailto:bulat.zigans...@gmail.com

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Ouch, my bad. length.show is better :) 2009/8/22 Derek Elkins : > 2009/8/22 Eugene Kirpichov : >> 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] >> > > round won't work

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

On Sat, Aug 22, 2009 at 12:31 PM, Derek Elkins wrote: > 2009/8/22 Eugene Kirpichov : >> 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] >> > > round won't work because 999

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

2009/8/22 Eugene Kirpichov : > 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] > round won't work because 999 is close to 1000. You simply need to use logBase 10 as a guess

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

Or better numDigits = length . show It's probably even faster. 2009/8/22 Eugene Kirpichov : > 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 : >>

Re: [Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

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 : > Ok. I wonder if someone could help me with this problem... > > I want to calculate the number of digits o

[Haskell-cafe] How to calculate de number of digits of an integer? (was: Is logBase right?)

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) = 2.9996 so numDigits 1000 = 2. Maybe adding a small amount