July 2016 1HaskellADay Problems and Solutions

July 2016

• July 28th, 2016: Lao Tzu says what is crooked cannot be made straight... but what does that guy know? Today's #haskell exercise
• July 27th, 2016: For today's #haskell exercise we look at the shortest distance between any two points in a graph. Today's #haskell solution uses brute-force to find shortest distance paths, which works for small graphs 
• July 26th, 2016: Today's #haskell exercise looks at (one aspect of) shortest pathing through graphs. Today's #haskell solution is the shortest path through a graph, NOT using continuations. *WHEW* 
• July 25th, 2016: For today's #haskell problem we look at pathing through graphs with cycles. We avoid 'teh Sadeness' with today's #haskell solution of pathing graphs with cycles 
• July 22nd, 2016: For today's #haskell exercise we tear apart #graph-construction or -pathing ... or both. Today's #haskell solution works PERFECTLY if your graph doesn't have cycles like this one! 
  
• July 21st, 2016: Today's #haskell problem looks at simplifying the representation of pathing through #graph data The #haskell solution paths through a graph, but ... hm: not perfectly. We'll look at complete pathing today.
• July 20th, 2016: Yesterday, I didn't give complete information for the figure. Today's #haskell exercise rectifies that #graph Today's #haskell solution is a #graph of complete information of the figure, and a partial look into pathing 
• July 19th, 2016: For today's #haskell exercise we count crows. I mean triangles ... I mean (properly) trigons 
  
• July 15th, 2016: I posted this problem on github this morning but did not announce:  #Haskell exercise: extract date from twitter JSON So, BANG! right on the heels of the exercise announcement: Data.Aeson and a little Day-parsing for the solution.
• July 14th, 2016: Today's #haskell exercise ... get this! ... helps you find Haskell exercises, both problems and solutions! #graph For today's #haskell solution I went the graph DaaS-route to extract @1HaskellADay problems and solutions 
• July 12th, 2016: Today's #haskell excercise compiles the RID into a Haskell module and analyzes Pride and Prejudice 
• July 11th, 2016: Today's #haskell exercise decodes the RID/Regressive Imagery Dictionary from JSON
• July 8th, 2016: Today's #haskell exercise brings together replacing one set of symbols with another and qualified names in XML  The #haskell solution today WEARYs me, but it, surprisingly, has COFFEE, so I'm good! Encoding strings-as-symbols.  
• July 7th, 2016: Today's #Haskell problem is to write Bram Stoker's Dracula as Jane Austen would have ... erhm, sort of. Not literature: a rehash of Bram Stoker's Dracula using Jane Austen's words .. but then: have you read the original? 
• July 6th, 2016: So, loading up an encoding table is on the plate for today's #haskell exercise. We encode Pride and Prejudice as symbols then save it as a #haskell module 
• July 5th, 2016: We look at encoding names and qualified names for today's #haskell exercise. For today's #haskell solution we encoded (qualified) names as symbols using SymbolTable 
• July 4th, 2016: (summary) Report generation is the name of the game for today's #haskell exercise. And so in today's #haskell solution we generate a report! BOOP! 
• July 1st, 2016: *WHEW* It took two days to marshall the data set for today's #haskell exercise: convert junit test result-XML to CSV And the #haskell solution involves TagSoup parsing at applicative functors 

1HaskellADay 1Liners June 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]

June 2016 1HaskellADay Problems and Solutions

• 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 
  
• June 23rd, 2016: Today we look at using #haskell to chart moving averages of a stock's prices https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D23/Exercise.hs https://twitter.com/logicalgraphs/status/743409829843243008 
  
• June 21th, 2016: I pushed today's #haskell problem last night on git but did I announce it? sigh Complex roots of quadratic equations https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D21/Exercise.hs The #haskell solution gives us the Complex roots to any (Real) quadratic equation https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D21/Solution.hs
• June 20th, 2016: Solving quadratic equations is on the plate for today's #haskell exercise https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D20/Exercise.hs 
  
  It's not every day I code
  [formula] <*> [(-),(+)] <*> [q]
  Thank you, #haskell, for today's solution to do so
  https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D20/Solution.hs
• June 17th, 2016: My, my! Where has the day flown? Today's #haskell problem is to reinvent charting API! ... or not. https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D17/Exercise.hs
• June 16th, 2016: Today's #haskell exercise looks at representing $TWTR data as candlesticks https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D16/Exercise.hs 
  
• June 15th, 2016: For today's #haskell problem, we round out the Data.Matrix module with the definition of the identity matrix https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D15/Exercise.hs There are many ways to define the identity matrix. Today's #haskell solution does so with Cellular Automata Rule 16 https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D15/Solution.hs
• June 14th, 2016: Yesterday we computed the matrix determinant, today we'll invert a matrix and use it to solve systems of equations https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D14/Exercise.hs Today's #haskell solution inverts a matrix BECAUSE WE FEEL LIKE IT! Yeah https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D14/Solution.hs
• June 13th, 2016: For today's #haskell problem we *ahem* DETERMINE (eventually) to solve systems of equations https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D13/Exercise.hs The determinant is the sum of the products of the first row with the sub-matrix determinants, right? RIGHT! https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D13/Solution.hs
• June 10th, 2016: Today's #haskell problem looks at box-and-whiskers charting of data https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D10/Exercise.hs Boxes for realz, yo: https://en.wikipedia.org/wiki/Box_plot The #haskell solution has @geophf writing 'uncurry uncurry' and sincerely meaning it! 😱 https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D10/Solution.hs and box: 
  
• June 9th, 2016: Triangles are on my mind for today's #haskell problem: https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D09/Exercise.hs … bisecting them, then trisecting them.
• June 8th, 2016: For today's #haskell problem, just what you've always wanted: MATH HOMEWORK! We find the intersection of two lines https://github.com/geophf/1HaskellADay/blob/master/exercises/HAD/Y2016/M06/D08/Exercise.hs
• ANNOUNCEMENT: lpaste.net is acting up; cloning original @1HaskellADay github repository and putting the exercise there. FYI
• June 6th, 2016: Today's #haskell problem explores superstring theory http://lpaste.net/6891096377267322880 No, it doesn't, but saying that has a certain ring to it!
• June 3rd, 2016: We saw a solution to perfect matching yesterday. For today's #haskell problem, let's efficient-ize it! http://lpaste.net/1128504074363207680
• June 1st, 2016: Today's #haskell problem is pretty much counting complements ... pretty much. http://lpaste.net/9130195410017583104 These apparently simple problems are actually rather hard. Today we have a #P-complete #haskell solution http://lpaste.net/670419007353913344