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mesbah095

Guest Post Online - 0 views

guestpostonline.com

haskell del.icio.us imported Tutorial functional programming reference intro monads howto

shared by mesbah095 on 03 Apr 14 - No Cached
  • mesbah095 on 03 Apr 14
     
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J.A. Alonso

The Risks and Benefits of Teaching Purely Functional Programming in First Year - 0 views

www.cse.unsw.edu.au/...CK02a.html

artículo enseñanza programación haskell

shared by J.A. Alonso on 26 Nov 11 - Cached
  • J.A. Alonso on 26 Nov 11
     
    "We argue that teaching purely functional programming as such in freshman courses is detrimental to both the curriculum as well as to promoting the paradigm. Instead, we need to focus on the more general aims of teaching elementary techniques of programming and essential concepts of computing. We support this viewpoint with experience gained during several semesters of teaching large first-year classes (up to 600 students) in Haskell. These classes consisted of computer science students as well as students from other disciplines. We have systematically gathered student feedback by conducting surveys after each semester. This article contributes an approach to the use of modern functional languages in first year courses and, based on this, advocates the use of functional languages in this setting. "
J.A. Alonso

Safe: De­bug­ging, Doc­u­ment­ing and Test­ing Haskell Pro­grams - 0 views

liamoc.net/safe.html

haskell artículo quickcheck

shared by J.A. Alonso on 26 Nov 11 - Cached
  • J.A. Alonso on 26 Nov 11
     
    This ar­ti­cle is a short piece ad­vo­cat­ing the use of Haskell based on the strength of its test­ing, de­bug­ging and doc­u­men­ta­tion tools.
Javier Neira

Understanding Haskell Monads - 0 views

ertes.de/monads.html

haskell monads tutorial learning

shared by Javier Neira on 16 Dec 09 - Cached
  • The opposite of referentially transparent is referentially opaque. A referentially opaque function is a function that may mean different things and return different results each time, even if all arguments are the same.
  • a function that just prints a fixed text to the screen and always returns 0, is referentially opaque, because you cannot replace the function call with 0 without changing the meaning of the program.
  • n fact, a function, which doesn't take any arguments, isn't even a function in Haskell. It's simply a value. A number of simple solutions to this problem exist. One is to expect a state value as an argument and produce a new state value together with a pseudorandom number: random :: RandomState -> (Int, RandomState)
  • ...12 more annotations...
  • A general purpose language is almost useless, if you can't develop user interfaces or read files. We would like to read keyboard input or print things to the terminal.
  • We have seen that we can solve this problem by expecting a state argument. But what's our state? The state of the terminal?
  • We seem to have found a useful solution to our problem. Just pass the state value around. But there is a problem with this approach.
  • A very special feature of Haskell is the concept of generalization. That means, instead of implementing an idea directly, you rather try to find a more general idea, which implies your idea as a special case.
  • However, the traditional programmer never had to face generalization. At most they faced abstraction,
  • they are a very abstract structure, which allows implementing functionality at an incredibly general level.
  • Haskell [1] is a purely functional programming language. Functions written in it are referentially transparent. Intuitively that means that a function called with the same arguments always gives the same result.
  • askell takes another approach. Instead of passing the world state explicitly, it employs a structure from category theory called a monad.
  • They are an abstract structure, and at first it can be difficult to understand where they are useful. The two main interpretations of monads are as containers and as computations.
  • The ⊥ value is a theoretical construct. It's the result of a function, which never returns, so you can't observe that value directly. Examples are functions, which recurse forever or which throw an exception. In both cases, there is no ordinary returning of a value.
  • Now that Nothing is a valid result, our function handles all cases.
  • You have some computation with a certain type of result and a certain structure in its result (like allowing no result, or allowing arbitrarily many results), and you want to pass that computation's result to another computation.
Javier Neira

Monads in 15 minutes: Backtracking and Maybe - 0 views

www.randomhacks.net/...monads-in-15-minutes

monads haskell backtracking howto

shared by Javier Neira on 09 Nov 09 - Cached
  • 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:
  • ...5 more annotations...
  • 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.
  • Backtracking: The lazy way to code
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