Snipplr

(Haskell) Linked List in C - rtperson

Sun, 02 Dec 2012 12:32:20 UTC

I bit of overkill for USACO's "Milk2" algorithm training problem. This problem would be better suited to an interval tree, but here it is.

(Haskell) Binary Search in Haskell - rtperson

Fri, 30 Nov 2012 14:16:50 UTC

Improved version, using lenses instead of the dangerous (!!) operator for list access.

(Haskell) Haskell 99 Problems - Problem 23 - rtperson

Sat, 10 Sep 2011 07:27:49 UTC

problem 23, Extract a given number of randomly selected elements from a list. Example: Prelude System.Random>rnd_select "abcdefgh" 3 >>= putStrLn "eda" Two problems: 1) How to return a list, and 2) how to sample without duplication

(Haskell) Haskell 99 Problems, numbers 1 through 9 - rtperson

Thu, 08 Sep 2011 00:23:54 UTC

I had originally started these problems from #10 (Run-length encoding). I went back and did 1-8 for completeness.

(Haskell) Haskell 99 Problems - Number 20, Arrowed! - rtperson

Thu, 25 Aug 2011 01:54:30 UTC

problem 20, (*) Remove the K'th element from a list *Main> removeAt 1 "abcd" "acd" Trivial using a pure function. A bit more challenging if you use this problem to work up your Arrow-fu.

(Haskell) Haskell 99 Problems - Number 17 - rtperson

Thu, 18 Aug 2011 06:50:09 UTC

problem 17, Split a list into two parts; the length of the first part is given. Do not use any predefined predicates. (Meaning no splitAt or take or drop) *Main> split "abcdefghik" 3 ("abc", "defghik")

(Haskell) Haskell 99 Problems - Numbers 15 and 16 - rtperson

Thu, 18 Aug 2011 03:59:30 UTC

problem 15, Replicate the elements of a list a given number of times. > repli "abc" 3 "aaabbbccc" problem 16, Drop every N'th element from a list. *Main> dropEvery "abcdefghik" 3 "abdeghk"

(Haskell) Haskell 99 Problems - Number 14 - rtperson

Thu, 18 Aug 2011 01:04:04 UTC

problem 14, Duplicate the elements of a list > dupli [1, 2, 3] [1,1,2,2,3,3]

(Haskell) Haskell 99 Problems - Solutions to 11 and 12 - rtperson

Fri, 29 Jul 2011 08:03:55 UTC

problem 11, modified run-length encoding ======================================== If an element has no duplicates, mark it as such. Example: encodeModified "aaaabccaadeeee" [Multiple 4 'a',Single 'b',Multiple 2 'c', Multiple 2 'a',Single 'd',Multiple 4 'e'] problem 12, Decode a run-length encoded list. ============================================= Given a run-length code list generated as specified in problem 11. Construct its uncompressed version. Example: decodeModified [Multiple 4 'a',Single 'b',Multiple 2 'c', Multiple 2 'a',Single 'd',Multiple 4 'e'] "aaaabccaadeeee"

(Haskell) Run-Length Encoding in Haskell - rtperson

Fri, 29 Jul 2011 06:08:49 UTC

Problem 10 of the famous 99 Problems. I got 99 problems, but a Lisp ain't one.

(Haskell) Towers of Hanoi by Bit Twiddling - rtperson

Thu, 07 Jul 2011 01:45:07 UTC

Credit where it's due: I got this from udpn over at codereview.stackexchange.com. I'm just putting it here for further study.

(Haskell) Towers of Hanoi in Haskell - rtperson

Thu, 07 Jul 2011 01:05:06 UTC

(Haskell) Real World Haskell Exercise - Ch 4 - rtperson

Wed, 01 Jun 2011 01:00:47 UTC

The first fold exercise from RWH, Chapter 4

(Haskell) Real World Haskell Exercise - Ch 4, Ex 2-4 - rtperson

Wed, 01 Jun 2011 00:59:27 UTC

I'm posting the rest of these, mostly because I'm still patting myself on the back for my point-free implementation of exercise 3, and because I give myself about two months before I entirely forget how I did it...

(Haskell) Fibonacci List One-Liner in Haskell - rtperson

Wed, 01 Jun 2011 00:44:37 UTC

I didn't invent this, but it's too cool a snippet not to capture. Here's a one-liner that will generate a list of Fibonacci numbers in linear time. EXPLANATION: the colon operator is used to add elements to a list, so it starts out adding on the two base cases, zero and one. After you have these two, you can mathematically generate the rest of the list. The zipWith function takes two lists and combines them using a function (in this case, addition). The two lists in question are fiblist (that is, the list you're currently generating) and "tail fiblist" (that is, every element of the list after the first element). The only reason this works is because Haskell's laziness gives it the ability to define infinite lists. Haskell will never even attempt to calculate the nth Fibonacci number until it is asked to do so.

(Haskell) Haskell Radix Conversion using ByteStrings - rtperson

Wed, 01 Jun 2011 00:30:19 UTC

Another radix conversion, when you need to zippy greatness of Haskell's ByteString.(Haskell strings are slooooow!) TODO: rewrite this using overloaded strings.

(Haskell) Haskell Radix Conversion - rtperson

Wed, 01 Jun 2011 00:26:01 UTC

Converts an integer from base 10 to a string of base x (where 0 > x >= 20). The only thing I'd improve is getting rid of all the calls to error. Perhaps hand back a Maybe String that simply hands back Nothing if unable to convert the number.

(Haskell) FizzBuzz in Haskell - rtperson

Wed, 01 Jun 2011 00:14:43 UTC

The dread FizzBuzz question -- really, a test if your average programmer knows his or her FOR loops. The spec is that you're counting from 1 to 100. Your program should print out "fizz" if the index is divisible by three, and "buzz" if it's divisible by five, and "fizzbuzz" if it's divisible by both. I have a couple different versions in this code: first, a few functions just fizzing or buzzing. Second, a generalization which allows any standard message against any divisor. Third, a purely functional version that zips two lists together (giving us free concatenation for "fizzbuzz"). Fourth, a list comprehension and lastly, a monadic version that calls a pure function that uses guards.