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HASKELL QUESTIONS

Haskell use main load a file , how to write address
Haskell use main load a file , how to write address
like below fixes the issue Here I have text file, I want to load it in Haskell, and read it in a List. , Under :help, you can see documentation for the :main command:
TAG : haskell
Date : November 24 2020, 11:01 PM , By : rajiv shrestha
remove the element from list
remove the element from list
I hope this helps you . makeList is a regular function, not a data constructor, so you can't pattern match on it. You need to pattern match on Cons and Nil; the fact that the list was returned by makeList isn't relevant.
TAG : haskell
Date : November 20 2020, 11:01 PM , By : Mr Babu
Type Specification in a Where Clause
Type Specification in a Where Clause
wish helps you Your last example is correct, but the type you wrote doesn't make sense. Num is a class constraint not a type. You probably wanted to write:
TAG : haskell
Date : November 19 2020, 11:01 PM , By : tfwynne
Is there a standard abstraction for this request-response type?
Is there a standard abstraction for this request-response type?
fixed the issue. Will look into that further It's Free Monad. The idea is that you have a description of instructions for which you can have multiple interpreters like your eval function. Free Monad abstracts over the pattern that this task has. For
TAG : haskell
Date : November 17 2020, 11:01 PM , By : Santa Ynez Valley
Modifying monad state
Modifying monad state
With these it helps For a programming exercise, I am supposed to take a Tree of data type , The problem is in
TAG : haskell
Date : November 16 2020, 11:00 PM , By : Guerilla Martinez
Write Quick Sort in Haskell and need help to resolve the issue
Write Quick Sort in Haskell and need help to resolve the issue
hope this fix your issue I try to write a quick sort in Haskell and I knew there are many versions out there. , I assume you use a file foo.hs and in it
TAG : haskell
Date : November 14 2020, 11:01 PM , By : Y. Raut
How to encode possible state transitions in type?
How to encode possible state transitions in type?
I wish this helpful for you What you're looking for is indeed Atkey's parameterised monad, now more commonly known as the indexed monad.
TAG : haskell
Date : November 13 2020, 11:01 PM , By : Aleksandr Balashov
Fail with basic usage of haskell stack
Fail with basic usage of haskell stack
around this issue It's not generally recommended to use a ghc version as a resolver, for the reason you've discovered: you need to manually specify lots of package versions. Instead, I'd recommend switching to lts-6.23, or something else similar.
TAG : haskell
Date : November 12 2020, 11:01 PM , By : Cheesy Monk
Haskell Gloss: time variable stays constant
Haskell Gloss: time variable stays constant
this will help Naturally it doesn't work, timeHandler receives a number which, in practice, is close to the time delta since the previous frame - the docs say: "A function to step the world one iteration. It is passed the period of time (in seconds)
TAG : haskell
Date : November 11 2020, 11:01 PM , By : Shako Kalatozishvili
How do I create a list of lists of pairs ordered and grouped by the second elements?
How do I create a list of lists of pairs ordered and grouped by the second elements?
will be helpful for those in need You can think of list comprehensions as [[(a, b) | b
TAG : haskell
Date : November 07 2020, 11:01 PM , By : naveena
How lambda function in unfoldr can be used with two arguments in Haskell?
How lambda function in unfoldr can be used with two arguments in Haskell?
I wish did fix the issue. When reading this article I found example of generating Fibonacci sequence with unfoldr function: , This is your function:
TAG : haskell
Date : November 05 2020, 11:01 PM , By : Ali Sajid
Are Haskell Pointers Pass by Value?
Are Haskell Pointers Pass by Value?
it should still fix some issue You don't free pointers, you free memory, specifically malloc (and co.)-allocated memory. If you free a pointer to something other than malloc-allocated memory, it fails. If you free a pointer to malloc-allocated memory
TAG : haskell
Date : November 04 2020, 04:05 PM , By : ching
validate field from database Yesod
validate field from database Yesod
Does that help Hi i want create a file that only accept values that exist in a table (with more that 20000 rows) so i have the following code , thanks @Michael Snoyman you are rigth I just have to use checkM
TAG : haskell
Date : November 02 2020, 11:01 PM , By : Y.Zhou
Simple Haskell Fibonacci function gets stuck
Simple Haskell Fibonacci function gets stuck
I wish this help you At the console, you haven't defined a single function fib with 3 different cases; you first defined fib 0 = 0, then overwrite that with a new function fib 1 = 1, then finally with a third function fib n = fib (n-1) + fib (n-2) th
TAG : haskell
Date : November 02 2020, 11:01 PM , By : chokwoo
what does the A stand for in sequenceA?
what does the A stand for in sequenceA?
Hope that helps The "A" stands for Applicative, as in the constraint in sequenceA's type:
TAG : haskell
Date : November 01 2020, 11:01 PM , By : yhadz
Create a recursive function that takes a list and uses it to create a List
Create a recursive function that takes a list and uses it to create a List
it fixes the issue I am very new in haskell and functional programming.I am trying to creat a recursive function that takes a list and uses it to create a List in the following way: , Do the following:
TAG : haskell
Date : October 31 2020, 05:38 PM , By : Brodricks Franklyn
Differences between Storable and Unboxed Vectors
Differences between Storable and Unboxed Vectors
around this issue Cribbed from https://haskell-lang.org/library/vectorStorable and unboxed vectors both store their data in a byte array, avoiding pointer indirection. This is more memory efficient and allows better usage of caches. The distinction b
TAG : haskell
Date : October 31 2020, 05:38 PM , By : TheJo0k3r
Recursively report the sum of the list if it contains exactly 3 odd numbers
Recursively report the sum of the list if it contains exactly 3 odd numbers
help you fix your problem I am new to haskell.I am trying to create a function that recursively report the sum of the list.Can sb help me? , List comprehension has another syntax:
TAG : haskell
Date : October 31 2020, 05:38 PM , By : Gudbrandr
Separating custom type values using functors?
Separating custom type values using functors?
may help you . The type of fmap for your data type would be (a -> b) -> Animals a -> Animals b. This very tightly constrains the possible implementations of fmap, so much that there is only one possible implementation that obeys the functor laws (fma
TAG : haskell
Date : October 31 2020, 09:54 AM , By : Couponsho Inc
Using functors/applicatives on custom data types with multiple type classes?
Using functors/applicatives on custom data types with multiple type classes?
I wish this help you Have a look at Data.Bifunctor for a type class for ADTs which are functorial in both arguments. User is then just a fancy name for tuple, and this already supports such an instance. Deriving a bifunctor instance is possible in Ha
TAG : haskell
Date : October 31 2020, 05:55 AM , By : Kavita Daswani
Redirections in Servant
Redirections in Servant
With these it helps There is one simple (but slightly hacky) answer, and a lead for making the first option obsolete (EDIT: and a third, better option, actually).The current typical solution for this is to simply use the fact that the Handler monad h
TAG : haskell
Date : October 25 2020, 04:08 PM , By : Otieno
Unit testing IO Int and similar in Haskell
Unit testing IO Int and similar in Haskell
around this issue There's a couple of things you can do. If you're using QuickCheck, you could write the following properties: The length of the returned list should be equal to the input length. All elements in the returned list should be elements o
TAG : haskell
Date : October 24 2020, 01:08 AM , By : Sam Maister
why does Haskell require numbers to be disambiguated for printf but not for show?
why does Haskell require numbers to be disambiguated for printf but not for show?
Hope this helps This is a quirk of the defaulting rules, which explicitly say that you may default a typeclass-polymorphic value to something monomorphic only when there are a fixed set of classes in the context:
TAG : haskell
Date : October 22 2020, 01:08 AM , By : Surya Prakash
Using Haskell Turtle's FilePath with readFile
Using Haskell Turtle's FilePath with readFile
I hope this helps you . The conversion can also be performed without directly using system-filepath:
TAG : haskell
Date : October 22 2020, 01:08 AM , By : user7446236
fetch environment variables in a cgi with haskell/hugs without a package
fetch environment variables in a cgi with haskell/hugs without a package
fixed the issue. Will look into that further I am writing a cgi-script in Haskell. I am restricted to use only hugs/runhugs. , Try import System.Environment (getEnv).
TAG : haskell
Date : October 20 2020, 03:08 PM , By : Pops00
Couldn't match expected type `[Char]' with actual type `a'
Couldn't match expected type `[Char]' with actual type `a'
With these it helps GHC is telling you an awful lot here. It seems to be saying something about y, right? And about (++)? So, what are the types of those things?
TAG : haskell
Date : October 20 2020, 03:08 PM , By : Yulia Lutlin
Cabal error `Unknown fields: build-tool-depends` trying to follow the servant tutorial
Cabal error `Unknown fields: build-tool-depends` trying to follow the servant tutorial
I wish this help you build-tool-depends is a new field of cabal 2.0. See What's new in Cabal/cabal-install 2.0
TAG : haskell
Date : October 20 2020, 01:08 AM , By : Chetan Dhanvij
Parse Error (Possibly Incorrect Indentation...)
Parse Error (Possibly Incorrect Indentation...)
This might help you Your if needs an else (what do you want the value to be when x isn't 1?).Furthermore do notation is used when working with monads and doesn't make sense in this function.
TAG : haskell
Date : October 19 2020, 03:08 PM , By : Sansa In Space
Summation in Haskell - functional programing
Summation in Haskell - functional programing
Hope that helps In your source file clase4.hs, the character you think is a standard ASCII minus sign in the expression n-1 isn't. Instead, you've probably used some other unicode character, like an "en dash" or something that only looks like a minus
TAG : haskell
Date : October 18 2020, 03:08 PM , By : twang
MonadRandom, State and monad transformers
MonadRandom, State and monad transformers
it helps some times Well how about an example to help you out. Since you didn't post a full working code snippet I'll just replace a lot of your operations and show how the monads can be evaluated:
TAG : haskell
Date : October 14 2020, 09:39 AM , By : Георгий Седометов
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