Posts tagged Haskell
Project Euler Problem 22
0Whilst trying Project Euler problems, I often write a prototype in Python before trying out an implementation in Haskell.
This problem however was screaming for “Functional Programming”.
In fact this time around, I started with a Haskell implementation and went on to translate to Python just for kicks. 🙂
Suffice to say, I am very pleased with myself. 😀
import Char
import List
names = [<List of names from problem specification>]
{- For each string s in list, Calculate sum of the characters’ alpha positions -}
sumChars :: [String] -> [Int]
sumChars [] = []
sumChars (x:xs) =
(foldl (\acc ltr -> acc + (ord(ltr)-ord(‘A’) + 1)) 0 x) : sumChars xs
main = do
let sortedNames = sort(names)
let zippedSumAndIndex = zip [1 .. length(sortedNames)] (sumChars sortedNames)
let total = foldl (\x y -> x + fst(y) * snd(y)) 0 zippedSumAndIndex
print total
More Haskell…
0So today, I was pondering How difficult it’d be to implement the Sieve of Eratosthenes in Haskell.
Turns out, very easy after all.. and more elegant.
sieve [] = []
sieve (x:xs) = x : sieve [p | p <- xs, p `mod` x /= 0]
So With that figured out, A new challenge was to solve this for any n. O’course, my earlier much simpler solution would have sufficed –
foldl (lcm) 1 [1..20]
But that doesn’t quite use my own implementation of the Sieve of Eratosthenes algorithm, does it?
So that needed to be corrected 😉
So here’s my solution –
For the love of Haskell…
0Haskell never fails to impress even the mediocre programmer in me.
Here’s something I have attempted solving using Haskell.
Problem –
Find the sum of all the even-valued terms in the Fibonacci sequence which do not exceed four million.
(Source: Project Euler problem 2)
(more…)
Look mom.. My first Haskell code
0These days I am trying my hardest to learn Haskell.
Found these 2 great online resources Real World Haskell and Learn You a Haskell.
An attempt to solve a rather simple problem from codechef took me close to 2 days.
Not due to the lack of looping constructs..
Nor because I cannot think recursively.
But primarily due to the fact that Haskell doesn’t make it easy to mix pure and impure code.
It took me quite a while to understand that a little monadic constructs such as mapM, forM exists. And the let bindings for sprinkling pure code in between impure code.