Wednesday, October 21, 2020

October 2020 Haskell 1-Liners

  • 2020-10-21: Curry `key` from
    secondPassFilter :: Ord a => a -> Set a -> Maybe b
    secondPassFilter key = spf key . Set.lookupGE key

    Given spf :: a -> Maybe a -> Maybe b
  • 2020-10-21: given: updater :: b -> Maybe b
    and firstPass :: Ord a => Map a b -> Map a b
    firstPass m = foldr (Map.update updater) m (Map.keys m)
    #Curry away `m` from the firstPass-function
    • Social Justice Cleric @noaheasterly
      firstPass = foldr (Map.update updater) <*> Map.keys
  • 2020-10-20: all (\c -> any (`isPrefixOf` c) setb) notinb
    #Curry away the `c` lambda argument.

Friday, October 9, 2020

October 2020 1HaskellADay Problems and Solutions

  • 2020-10-27: Military alliances from a @wikidata query.
  • 2020-10-26: Today's #haskell problem captures the Cypher of countries, continents, and airbases.
  • 2020-10-23: Today's #haskell problem: "Unicode? What, even, is that?" ... sez Haskell, smh.  Also, if you know how to get Text not to escape unicode points on output (to, say, a REST endpoint), much obliged if you told me this dark magic. Today's #haskell solution shows airbases (with their associated countries) added to the graph database

  • 2020-10-20: Next evolutionary step. We have Continents and countries as data structures. For today's #haskell problem let's find out how we can (can't?) merge in airbases with countriesHoo, doggies! "Upload airbases to the graph database!" he said. "It'll be easy!" he said. Today's #haskell solution, if not in book-form, then in book-length! 
  • 2020-10-16: Map of a -> b or b -> a? ... If you're asking that question, why not Graph? Today's #haskell exercise. A mapping of continents to countries. Surprisingly, wikidata.org does not have this as data amenable to extraction. 

  • 2020-10-15: From continent->country mapping to country->continent mapping for today's #haskell problem. `sequence` is the secret-sauce for today's #haskell solution. 
  • 2020-10-14: Today's #haskell problem is to get countries by continent from a ... 'markdown' file? That is not markdown. Deal with it. Countries: meet your Continents. 
  • 2020-10-13: Okay. #StringsAreWrong. Everybody knows this. Wikidata: "Let's encode LongLats as strings ... IN JSON!" Please let's not. Today's #haskell exercise. The solution that produces airbases with lat/longs. REAL lat/longs, smh. 
  • 2020-10-12: Today's #haskell problem is airbases of the world from wikidata.org ... with some duplicates. Today's #haskell solution reads in JSON, even ... 'JSON' that encodes 'LongLat's (not lat/longs) as ... strings? Really? Yes, even points-as-strings. Remember: #StringsAreWrong ~ Richard A. O'Keefe, 26 April 1994 
  • 2020-10-09: Today's #haskell problem is this: Production data: "Let's see if we can make the simple act of parsing a 'JSON file' [that isn't a JSON file] impossible for the ol' el geophf!" Nice try, production data. Nice try. 

Wednesday, September 2, 2020

September 2020 Haskell Problems and Solutions

Tuesday, September 1, 2020

February 2019 Haskell 1-liners

 

  • February 18th, 2019:
    Define ext :: (Maybe a, b) -> Maybe (a,b)
    e.g.: ext (Just 5, "Hi") = Just (5, "Hi")
    • Al͜l ̸͑ha͂͟il̶! @TechnoEmpress \o/ 
    • cλementd @clementd `fmap swap. sequenceA . swap` :-)
    • Raveline @Raveline bisequence . second pure
    • Alexey Radkov @sheshanaag uncurry (flip $ fmap . flip (,))
    • a fool @fresheyeball ext = \case (Just x, y) -> Just (x, y); _ -> Nothing

September 2020 Haskell 1-liners

  • 2020-09-08: given

    removeInfreqs :: Set String -> Ontology -> Ontology
    removeInfreqs infrequentWords ont = 
       Map.map (\wordcounts -> foldl (flip ri') wordcounts infrequentWords) ont

    where Ontology is a map-of-maps.

    1. remove flip to get the same functional result.
    2. curry away ont from the function removeInfreqs
    3. curry away wordcounts from the map-lambda function.
    4. curry away infrequentWords from the function removeInfreqs

      n.b.: This curry may not be as straightforward as the other curries.

  • 2020-09-01: Given all of the above, and now that you've curried the above lambda to [SPOILER]:

    \key -> const (not (Set.member key stoppers))

    Curry away key from this new lambda.

Wednesday, August 26, 2020

August 2020 1HaskellADay 1Liners

  • 2020-08-31:

    #Haskell #BetterWithCurry #1Liner For:
    >>> :t Map.filterWithKey 
    Map.filterWithKey :: (k -> a -> Bool) -> Map k a -> Map k a

    we have this filtering function: \key _val -> not (Set.member key stoppers)

    _val is unused. Curry it away.

  • 2020-08-28: 
    rmFront :: Set Char -> String -> String
    rmFront weirds str = dropWhile (flip Set.member weirds) str
    Simple currying questions: can this function-implementation be simplified with currying? Can it be simplified ... MORE? Answers: yes, and yes. Show your implementation.

  • 2020-08-26: We have this: \info -> importBook info >>= return . (info,) There are way too many info-references. What's a better way to write this expression?
    • Five solutions from @noaheasterly:
      • runKleisli (id &&& Kleisli importBook)
      • liftA2 (liftA2 (,)) return importBook
      • liftA2 (fmap . (,)) id importBook
      • traverse importBook . join (,)
      • traverse importBook . (id &&& id)

Monday, August 3, 2020

August 2020 1HaskellADay Problems and Solutions