## Saturday, December 10, 2016

• October 21st, 2016:
You have l1 :: [(v, [(k, x)])]
You need the transformation l2 :: [(k, [(v, x)])]
Redistribute v and k in one line
Props for elegance
• Francisco T @aiceou redist xs = fromListWith (++) \$ concat \$ (map f xs) where f (a,ys) = map (\(x,y) -> (x,[(a,y)])) ys ... but k has to be 'Ord'

## Saturday, October 22, 2016

• September 15th, 2016:
Given [1..n], create an infinite list of lists [[1.. n], [n+1 ... n+n], [n+n+1 ... 3n], ...]
counting :: [Integer] -> [[Integer]]
• joomy @cattheory
counting = (map . (+) . fromIntegral . length) >>= iterate
• September 30th, 2016: The reverse of August's one-liner:
f :: (Maybe a, b) -> Maybe (a,b)
define f. Snaps for elegance.

## Thursday, September 15, 2016

• August 20th, 2016: maybeify :: (a, Maybe b) -> Maybe (a, b)
Define maybeify. Snaps for elegance.
• Hardy Jones @st58 sequence
• Thomas D @tthomasdd {-# LANGUAGE TupleSections #-}
mabeify (x,mY) = maybe Nothing (return . (x,)) mY
• Андреев Кирилл @nonaem00 import "category-extras" Control.Functor.Strong
maybeify = uncurry strength
• bazzargh @bazzargh I can't beat 'sequence', but: uncurry (fmap.(,))
• Nick @crazy_fizruk distribute (from Data.Distributive)

## Thursday, September 1, 2016

### August 2016

• August 25th, 2016: Today's #haskell exercise looks at historical prices of #bitcoin
Today's #haskell solution is worth \$180k ... five years ago. I wonder what it will be worth 5 years hence?

• August 23rd, 2016: Enough diving into the node's data, let's look at the structure of the related nodes for today's #haskell problem. The structure of tweets and related data for today's #haskell solution
• August 22nd, 2016: Today's #haskell problem is parsing twitter hashtags and a bit of data fingerprinting/exploration of same. BOOM! Today's #haskell solution analyzes hashtags twitter-users ('tweeps') use
• August 19th, 2016: For today's #haskell exercise we look at unique users in a set of twitter graph-JSONToday's #haskell solution gives us a list of users, then their tweets, from twitter graph-JSON data
• August 18th, 2016: For today's #haskell problem we extract and reify URLs from twitter graph-JSON. Today's #haskell solution extract URLs from twitter data as easily as looking up the URLs in a JSON map.
• August 17th, 2016: For today's #haskell problem we explore the relationships from and to tweets and their related data. Today's #haskell solution relates data to tweets extracted from graph-JSON
• August 16th, 2016: For today's #haskell exercise we begin converting nodes in a graph to more specific types (Tweets are up first). We create some JSON Value-extractors and with those find the tweets in graph JSON in today's #Haskell solution
• August 15th, 2016: Today's #haskell exercise looks at twitter data as labeled/typed nodes and relations in JSON

Okay! For today's #haskell solution we discover our node and relation types in twitter data-as-graphs JSON!
• August 10th, 2016: Today's #Haskell problem we look at the big data-problem: getting a grasp of large indices of tweets in graph JSON. Today's #Haskell solution time-stamps and gives 'small-data' indices to tweets from graph JSON
• August 9th, 2016: For today's #haskell problem we extract the tweets from rows of graph data encoded in JSON. Today's #Haskell solution extracts the tweets from graph JSON and does some simple queries
• August 8th, 2016: For today's #haskell problem we look at reading in the graph of a twitter-feed as JSON and just a bit of parsing. We leverage the Cypher library for today's #haskell solution to look at 100 rows of tweets encoded as JSON
• August 5th, 2016: Today's #Haskell problem we go for the Big Kahuna: solving a Kakuro puzzle
Okay, we have a #Haskell solution ... finally ... maybe. The solver took too long, so I solved it myself faster :/
• August 4th, 2016: Today's #Haskell exercise looks at (simple) constraints of unknown values for a sum-solverToday's #Haskell solution also uses QBits to solve constrained unknowns
• August 3rd, 2016: Today's #haskell problem provides the cheatsheet: "What are the unique 4-number sums to 27?" We round-trip the Set category for today's #haskell solution
• August 2nd, 2016: Today's #haskell exercise looks at solving our sums when we know some of the numbers alreadyQBits actually work nicely for today's #Haskell solution
• August 1st, 2016: For today's #Haskell exercise we play the 'Numbers Game.' The #haskell solution is a guarded combine >>= permute in the [Int]-domain. I like the Kleisli category; ICYMI.
• ## Saturday, August 20, 2016

### 1Liners for July 2016

• July 14th, 2016: So you have x :: [a] in the IO monad, and the function f :: a -> b What is the expression that gets you IO [b]?

## Thursday, July 14, 2016

• June 13th, 2016:
You want this list: `[1, -1, 1, -1, ...]`
How would you produce this value in #Haskell ?
• Wai Lee Chin Feman @wchinfeman
https://gist.github.com/skatenerd/08d70c45499e1610206a
(set plop to be identity, and set transformstate to be (*) -1)
• Philipp Maier @AkiiZedd ``iterate negate 1`
• Patrick Mylund @pmylund `concat \$ repeat [1, (-1)]`
• Gary Fixler @gfixler No need for the parens in a list.
• Jeff Foster @fffej and Kevin Meredith @Gentmen
`iterate (* (- 1)) 1`
• Spencer Janssen @spencerjanssen and Андреев Кирилл @nonaem00
`cycle [1, -1]`
• Philipp Maier @AkiiZedd:
I’m curious: Since concat is O(n) wouldn’t it take more and more time depending on how many items you take?
• Patrick Mylund @pmylund Looks like they compile to the same thing https://gist.github.com/patrickmn/9a92ab2a088018b2c0631f3bcfd60ebe
• Philipp Maier @AkiiZedd I’m actually surprised the compiler can optimise this away :o Thanks for showing me `ddump-simpl`!
• Eyal Lotem @EyalL `concat` is `foldr (++)`, not `foldl`. O(1) work is done to produce the next item. `[1,-1]++([1,-1]++(...`
• David Turner @DaveCTurner I'd actually write '`cycle [1,-1]`' but I like the elegant, alliterative obscurity of   '`iterate negate 1`'
• Fatih Karakurt @karakfa `alt=1:[-x|x<-alt]`

## Friday, July 1, 2016

• June 29th, 2016: Today's #Haskell exercise is REALLY HARD! ... for Big Gov't. Can you solve it? A little bit of (well-typed) Prolog-like code gets us our #haskell solution for today
• June 28th, 2016: For today's #haskell problem we do ... NOTHING! But we are introduced to coding software for a huge bureaucracy  ... AAAAANNNDDD three System imports and we've got today's #haskell solution. Groovy!
• June 24th, 2016: #haskell problem today charts Stochastic Oscillators of a security  and includes a 'malus' problem: report generation
It's not every day I code
Thank you, #haskell, for today's solution to do so