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Javier Neira's List: uned_declarative_programming

Monads in 15 minutes: Backtracking and Maybe

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monads haskell backtracking howto on 2009-11-23 and saved by 5 people
- Add Sticky Note
- Backtracking: The lazy way to code
- 7 more annotations...
- - type Choice a = [a]
    
    choose :: [a] -> Choice a
    choose xs = xs
  - Because Haskell doesn’t compute answers until we ask for them, we get the
    actual backtracking for free!
  - The missing function is almost too trivial to mention: Given a single value of
    type a, we need a convenient way to construct a value of type
    Choice a:
  - More math trivia: return is also known as unit
    and η. That’s a lot of names for a very simple idea.)
  - makePairs =
    choose [1,2,3] >>= (\x ->
    choose [4,5,6] >>= (\y ->
    return (x,y)))
  - makePairs' = do
    x <- choose [1,2,3]
    y <- choose [4,5,6]
    return (x,y)
  - Every monad has three pieces: return, map and
    join.
Fatvat: Building Basic Types in Haskell

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haskell types basic building howto on 2009-11-09
Fatvat: Generating Text in Haskell

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haskell text generating fatvat basic string on 2009-11-09
Learn You a Haskell for Great Good! - Introduction

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haskell tutorial good on 2009-04-14 and saved by 3 people
A Gentle Introduction to Haskell: Arrays

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haskell introduction array type on 2009-11-09
The Haskell 98 Language Report

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haskell libraries reference on 2009-12-07
The Haskell 98 Library Report: Arrays

-- A rectangular subarray
subArray :: (Ix a) => (a,a) -> Array a b -> Array a b
subArray bnds = ixmap bnds (\i->i)

-- A row of a matrix
row :: (Ix a, Ix b) => a -> Array (a,b) c -> Array b c
row i x = ixmap (l',u') (\j->(i,j)) x where ((_,l'),(_,u')) = bounds x

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haskell library Array reference on 2009-12-02
- 16.2 Incremental Array Updates
  
  The operator (//) takes an array and a list of pairs and returns
  an array identical to the left argument except that it has
  been updated by the associations in the right argument. (As with
  the array function, the indices in the association list must
  be unique for the updated elements to be defined.) For example,
  if m is a 1-origin, n by n matrix, then
  m//[((i,i), 0) | i <- [1..n]] is the same matrix, except with
  the diagonal zeroed.
- -- A rectangular subarray
  
  subArray :: (Ix a) => (a,a) -> Array a b -> Array a b
  
  subArray bnds = ixmap bnds (\i->i)
  
  -- A row of a matrix
  
  row :: (Ix a, Ix b) => a -> Array (a,b) c -> Array b c
  
  row i x = ixmap (l',u') (\j->(i,j)) x where ((_,l'),(_,u')) = bounds x
  
  -- Diagonal of a matrix (assumed to be square)
  
  diag :: (Ix a) => Array (a,a) b -> Array a b
  
  diag x = ixmap (l,u) (\i->(i,i)) x
  
  where
  
  ((l,_),(u,_)) = bounds x
  
  -- Projection of first components of an array of pairs
  
  firstArray :: (Ix a) => Array a (b,c) -> Array a b
  
  firstArray = fmap (\(x,y)->x)
Arrays - HaskellWiki

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haskell library Array reference examples on 2009-11-10
Haskell - Wikibooks, collection of open-content textbooks

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haskell programming wiki book tutorial on 2009-09-27 and saved by 23 people
99 questions/1 to 10 - HaskellWiki

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haskell questions howto 99 on 2009-11-11
- data NestedList a = Elem a | List [NestedList a]
  
  flatten :: NestedList a -> [a]
  flatten (Elem x) = [x]
  flatten (List x) = concatMap flatten x
- compress :: Eq a => [a] -> [a]
  compress = map head . group
  
  We simply group equal values together (group), then take the head of each.
  Note that (with GHC) we must give an explicit type to compress otherwise we get:
P-99: Ninety-Nine Prolog Problems

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prolog exercises programming examples on 2009-11-10 and saved by 11 people
List comprehension - HaskellWiki

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haskell list comprehension reference on 2009-11-10
Hashiowakero.hs

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haskell puzzle example exercise on 2009-11-12
Haskell-mode for Emacs

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haskell emacs mode reference on 2009-11-13
Haskell: The Confusing Parts

If you’re used to the C family of languages, or the closely related family of “scripting languages,” Haskell’s syntax (mainly) is a bit baffling at first. For some people, it can even seem like it’s sneaking out from under you every time you think you understand it. This is sort of a FAQ for people who are new to Haskell, or scared away by its syntax.

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haskell intro good syntax on 2009-11-15 and saved by 7 people
- I will point out that return is, in fact, not a return
  statement. It’s a function, and an inappropriately named function, at that.
  Writing return () in your do block will
  not cause the function to return.
- The curry and uncurry functions stand in for \f x y -> f (x, y)
- 7 more annotations...
- - putStrLn (take 12 (map foo (bar ++ "ack")))
    
    -- ...can be rewritten as...
    putStrLn $ take 12 $ map foo $ bar ++ "ack"
    
    (putStrLn . take 12 . map foo) (bar ++ "ack")
    
    putStrLn . take 12 . map foo $ bar ++ "ack"
  - putStrLn (take 12 (map foo (bar ++ "ack")))
  - anywhere you might write \x -> foo x [1..10], you should instead
    write flip foo [1..10], where flip is a standard
    Prelude function that flips the first two arguments of whatever
    function you give it
  - The curry and uncurry functions stand in for \f x y -> f (x, y) and \f (x, y) -> f x y, respectively.
  - anywhere you might write \x -> foo x [1..10], you should instead
    write flip foo [1..10], where flip is a standard
    Prelude function that flips the first
  - -- Actual definitions: f $ x = f x (f . g) x = f (g x) -- Some quick examples of using these. The following line... putStrLn (take 12 (map foo (bar ++ "ack"))) -- ...can be rewritten as... putStrLn $ take 12 $ map foo $ bar ++ "ack" (putStrLn . take 12 . map foo) (bar ++ "ack") putStrLn . take 12 . map foo $ bar ++ "ack"
  - two arguments of whatever
Haskell Hierarchical Libraries

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haskell libraries reference ghc on 2009-11-15 and saved by 5 people
How do you combine filter conditions - Stack Overflow

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haskell combine filter condition on 2009-11-16
Haskell 98 Prelude Index

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haskell prelude 98 reference on 2009-11-16
Type - HaskellWiki

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type haskell wiki data on 2009-11-17
- data Suit = Club | Diamond | Heart | Spade
  deriving (Read, Show, Enum, Eq, Ord)
  
  data CardValue = Two | Three | Four
  | Five | Six | Seven | Eight | Nine | Ten
  | Jack | Queen | King | Ace
  deriving (Read, Show, Enum, Eq, Ord)
- data Card = Card {value::CardValue,
  suit::Suit}
  deriving (Read, Show, Eq)
- 1 more annotations...
- - type Deck = [Card]
    
    deck::Deck
    deck = [Card val su | val <- [Two .. Ace], su <- [Club .. Spade]]
Data.Map

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data map haskell reference on 2009-11-17

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Javier Neira

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Updated on 2009-12-30
Created on 2009-11-09

Category: Computers & Internet

functional programming declarative uned haskell prolog

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Javier Neira's List: uned_declarative_programming

Monads in 15 minutes: Backtracking and Maybe

Fatvat: Building Basic Types in Haskell

Fatvat: Generating Text in Haskell

Learn You a Haskell for Great Good! - Introduction

A Gentle Introduction to Haskell: Arrays

The Haskell 98 Language Report

The Haskell 98 Library Report: Arrays

16.2 Incremental Array Updates

Arrays - HaskellWiki

Haskell - Wikibooks, collection of open-content textbooks

99 questions/1 to 10 - HaskellWiki

P-99: Ninety-Nine Prolog Problems

List comprehension - HaskellWiki

Hashiowakero.hs

Haskell-mode for Emacs

Haskell: The Confusing Parts

Haskell Hierarchical Libraries

How do you combine filter conditions - Stack Overflow

Haskell 98 Prelude Index

Type - HaskellWiki

Data.Map

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