Daniel, There are included as gists on the link provided. After your remark, I looked at the generated html code in my blog. The gists are actually displayed by running a javascript. Maybe your browser settings don't allow to display them. If so, you can also look directly at the gists: pb 01: https://gist.github.com/1161280 pb 02: https://gist.github.com/1161302 pb 03: https://gist.github.com/1161406 pb 04: https://gist.github.com/1161435 pb 05: https://gist.github.com/1161450 pb 06: https://gist.github.com/1163746 pb 07: https://gist.github.com/1163835 pb 08: https://gist.github.com/1163872 pb 09: https://gist.github.com/1166852 pb 010: https://gist.github.com/1172509 pb 011: https://gist.github.com/1172521 On Sat, Aug 27, 2011 at 4:47 AM, Daniel Fischer wrote:

On Saturday 27 August 2011, 02:34:24, Oscar Picasso wrote:

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Hi,

I order to improve my Haskell skills I started (again) to solve the project euler problems with this language. I am now at problem 11 and would really appreciate any comment about my code in order to make it more elegant or efficient.

I don't see any code, where would I have to look?

...

My solutions can be found here: http://fp.opicasso.com/tag/projecteuler

Oscar Picasso

Daniel, Thank you very much for your comments, there are very useful, indeed. As a side note, my domain name is not oscarpicasso.com. It was already taken by someone else so I decided to use opicasso.com Oscar On Sat, Aug 27, 2011 at 11:05 AM, Daniel Fischer wrote:

On Saturday 27 August 2011, 16:03:46, Oscar Picasso wrote:

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Daniel,

There are included as gists on the link provided. After your remark, I looked at the generated html code in my blog. The gists are actually displayed by running a javascript. Maybe your browser settings don't allow to display them.

NoScript :) I allowed oscarpicasso.com, but didn't look far enough to allow github.com.

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On Sat, Aug 27, 2011 at 4:47 AM, Daniel Fischer

wrote:

...

On Saturday 27 August 2011, 02:34:24, Oscar Picasso wrote:

...

Hi,

I order to improve my Haskell skills I started (again) to solve the project euler problems with this language. I am now at problem 11 and would really appreciate any comment about my code in order to make it more elegant or efficient.

In problem 11, by regarding all 4x4 subgrids separately, you recompute most of the horizontal and vertical products up to four times. Also you repeatedly use length and (!!). For a problem with such small parameters, it doesn't matter much, but consider a 1000x1000 grid with 100x100 subgrids, it would really hurt then. You could get much better performance (and no worse code) by using an array for the grid.

horizontalProd size grid row col    = product [grid!(row, col+i) | i <- [0 .. size-1]]

verticalProd size grid row col    = product [grid!(row+i, col) | i <- [0 .. size-1]]

seProd size grid row col    = product [grid!(row+i, col+i) | i <- [0 .. size-1]]

neProd size grid row col    = product [grid!(row-i, col+i) | i <- [0 .. size-1]]

maxProd size grid rows cols    = maximum $         [horizontalProd size grid row col             | row <- [0 .. rows-1], col <- [0 .. cols-size]]      ++ [verticalProd size grid row col             | col <- [0 .. cols-1], row <- [0 .. rows-size]]      ++ [seProd size grid row col             | row <- [0 .. rows-size], col <- [0 .. cols-size]]      ++ [neProd size grid row col             | row <- [size-1 .. rows-1], col <- [0 .. cols-size]]

Another thing,

slice n = takeWhile ((n ==) . length) . map (take n) . tails

if you also import tails from Data.List.

Concerning the newly posted problem 12: Yes, it would be much faster to count the divisors using the prime factorisation (plus, there's another speedup available if you go that route).

...

...

I don't see any code, where would I have to look?

...

My solutions can be found here: http://fp.opicasso.com/tag/projecteuler

Oscar Picasso