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    Is there a way to compare two functions for equality? For example, (λx.2*x) == (λx.x+x) should ... true, because those are obviously equivalent. See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I have long been wondering why lazy evaluation is useful. I have yet to have anyone explain to me in a way ... Note: I do not mean memoization. See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I have twice recently refactored code in order to change the order of parameters because there was too much code ... the best use of currying? See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Consider a single-linked list. It looks something like data List x = Node x (List x) | End It is ... most commonly-used example of folding. See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    split :: [a] -> Int -> ([a], [a]) split [xs] n = (take n [xs], drop n [xs]) The same code works if ... under the hood. Test input: [1,2,3] 2. See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Here is a way to solve Euler problem 43 (please let me know if this doesn't give the correct answer). Is ... 9] main = do print $ pandigitals See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    (.) takes two functions that take one value and return a value: (.) :: (b -> c) -> (a -> b) -> a - ... say it is that the types don't match up. See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Is there a built-in function with signature :: (Monad m) => m a -> a ? Hoogle tells that there is no such function. Can you explain why? See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I am trying to learn Scala now, with a little bit of experience in Haskell. One thing that stood out as odd ... type that defines a + operator? See Question&Answers more detail:os...
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    I was just doing some Haskell development and I recompiled some old code on a new version of GHC: The ... the same or similar functionality? See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I was a bit confused by the documentation for fix (although I think I understand what it's supposed to do now), ... ). What am I doing wrong? See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    What is indexed monad and the motivation for this monad? I have read that it helps to keep track of the side ... (or any other valid example)? See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I started my Grand Haskell Crusade (GHC :) ) and I am a bit confused with monads and IO functions. Could anyone explain ... f2 [[1,2],[2,3]] See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'm a Haskell beginner, I'm just beginning to wrap my head around Monads, but I don't really get it ... the interpreter and fails when compiled. See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    In many articles about Haskell they say it allows to make some checks during compile time instead of run time. So, I ... zero. How can I do it? See Question&Answers more detail:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I've been going through the Typeclassopedia to learn the type classes. I'm stuck understanding Alternative (and ... or means something different -- from Monoid. Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Reading through this classic paper, I'm stuck on paramorphisms. Unfortunately the section is quite thin, and ... as references, but not as learning materials. Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I want to make a function that displays the last element of a list. This is my code: ghci> let myLast ... I have included all the possibilities. Any ideas? Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    How do I explicitly import typeclass instances? Also, how do I do this with a qualified import? ... because the Monad instance is implicitly imported. Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    At different questions I've found hints in comments concerning using the (->) instance of Monads e.g. for ... Haskell somewhere involves (->) or "Monad". Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    It is well-known that applicative functors are closed under composition but monads are not. However, I have been ... a proof of the above example in particular. Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    In Real World Haskell, Chapter 4. on Functional Programming: Write foldl with foldr: -- file: ch04/Fold.hs ... uses 3 parameters, I'm complelely confused! Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    The code for the myAny function in this question uses foldr. It stops processing an infinite list when the ... the function behaves. How is this wrong? Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Who first said the following? A monad is just a monoid in the category of endofunctors, what's the problem ... who doesn't have much Haskell experience)? Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I typed the following into ghci, thinking that one of two things would happen: 1) The interpreter would hang ... a finite comprehension out of an infinite list? Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I am not really proficient in Haskell, so this might be a very easy question. What language ... functions in Haskell already support polymorphic arguments? Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I am having problem in entering multi-line commands in ghci. The following 2-line code works from a file: addTwo :: ... I am using WinGHCi, version 2011.2.0.1 Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I've generally heard that production code should avoid using Lazy I/O. My question is, why? Is it ever OK ... makes the alternatives (e.g. enumerators) better? Question&Answers:os...
asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)
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