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HASKELL QUESTIONS

Can Haskell's Opaleye DSL generate any given SQL?
Can Haskell's Opaleye DSL generate any given SQL?
wish helps you According to the Opaleye tutorial, creating tables and databases is currently unsupported:
TAG : haskell
Date : November 21 2020, 03:00 PM , By : Douglas N. BK
Threepenny-gui: get file path via 'file' input
Threepenny-gui: get file path via 'file' input
seems to work fine As far as I know, web browsers do not allow you to obtain a filepath via the fields, for reasons of security. You can only obtain the file contents. Of course, you can always ask for a filepath in a plaintext input field, but that
TAG : haskell
Date : November 19 2020, 03:01 PM , By : Alexandra Dra
How can I return a list from list of list Haskell
How can I return a list from list of list Haskell
this will help Your immediate problem is that checkPerm is returning an empty list of type [Char], not [Int], when it gets an empty list as its second argument.However, checkPerm is basically reimplementing Data.List.find.
TAG : haskell
Date : November 17 2020, 03:01 PM , By : Wenqi Ong
Making Monad type showable
Making Monad type showable
I hope this helps . I am making a maze generator and wish to visualize the maze by printing. I have a wall type and a function that generates a random maze of those walls. , You will want your pretty printer to have type:
TAG : haskell
Date : November 17 2020, 03:01 PM , By : Adonis Sampaio
The usage of monad transformers
The usage of monad transformers
it helps some times The author tries to say that the composition of any two monads isn't possible. This isn't because language is bad, but because there are monads whose composition isn't a monad.For instance, IsntMonad isn't a monad:
TAG : haskell
Date : November 15 2020, 03:01 PM , By : Uwe Ritter
How to create a generic Complex type in haskell?
How to create a generic Complex type in haskell?
it should still fix some issue Traditional data in Haskell is just that: data. It doesn't need to know anything about the properties of its fields, it just needs to be able to store them. Hence there's no real need to constrain the fields at that poi
TAG : haskell
Date : November 11 2020, 03:01 PM , By : clgo
EAN13 Barcode Encoding in Haskell: How to test it?
EAN13 Barcode Encoding in Haskell: How to test it?
Hope this helps You have two bugs in your implementation:First, in encodeDigits, you've written splitAt 5 when it should be splitAt 6. This fixes the encoding bug noted by @Brian Anderson.
TAG : haskell
Date : November 11 2020, 03:01 PM , By : Zhaolin Xu
How to implement the Arbitrary instance for data type like this?
How to implement the Arbitrary instance for data type like this?
should help you out I am new to Haskell, I am trying to write a test case to prove the associative law for Semigroup typeclass. , You can exploit the predefined instance for functions.
TAG : haskell
Date : November 10 2020, 03:01 PM , By : Nataly Costa
How to use Parsers from Aeson with IO
How to use Parsers from Aeson with IO
help you fix your problem Well, I don't know if it's a good idea, and juggling the extra IO layer will certainly get frustrating as heck for larger developments, but the following type-checks:
TAG : haskell
Date : November 07 2020, 03:01 PM , By : Chris Peacock
Split a tuple into n parts
Split a tuple into n parts
this one helps. This is similar to @mschmidt's answer, but I think a list comprehension is probably clearest:
TAG : haskell
Date : November 06 2020, 03:01 PM , By : M.Piedmont
Xmonad - How do I move mouse pointer as part of ManageHook?
Xmonad - How do I move mouse pointer as part of ManageHook?
wish of those help You can use liftX to turn an X action into a Query action. You probably want to use XMonad.Actions.Warp instead of X.A.UpdatePointer instead, though; the latter looks like it might do a bit too much magic to sensibly fire during a
TAG : haskell
Date : November 04 2020, 03:01 PM , By : sumit kumar
Idiomatic way to have many of the same generators in a list comprehension
Idiomatic way to have many of the same generators in a list comprehension
hop of those help? If your concern is the [1..6] repetition (the ability for the range to vary independently), you could use:
TAG : haskell
Date : November 02 2020, 03:01 PM , By : Alexey Apukhtin
Tree construction from a node string (Can't understand this Haskell code)
Tree construction from a node string (Can't understand this Haskell code)
wish help you to fix your issue First, I agree with the comments: don't try to understand this "solution" until you've been using Haskell for a few years. For the sake of completeness, though, here's how to use it...This solution is implemented as a
TAG : haskell
Date : October 31 2020, 04:00 PM , By : Natalie Beckham
Give a default value for fields not available in json using aeson
Give a default value for fields not available in json using aeson
may help you . If you can't load that structure from JSON, then don't define it this way! Make it
TAG : haskell
Date : October 31 2020, 04:00 PM , By : Pang Boon
grouping a list of lists by their first element
grouping a list of lists by their first element
hop of those help? First let's note that instead of writing your explicitly named comp, it's easier to use the on combinator:
TAG : haskell
Date : October 24 2020, 08:10 PM , By : Anubhuti_148
Reading Lines Asynchronously in Haskell
Reading Lines Asynchronously in Haskell
Hope this helps I am trying to read lines without blocking using Async. I have figured out how to read one line, but I don't know the correct approach to make this continuous. Ideally I would like to have a generator that I could read the next line w
TAG : haskell
Date : October 19 2020, 08:10 PM , By : user2173887
How do I enforce run-time conditions on data in Haskell?
How do I enforce run-time conditions on data in Haskell?
I wish did fix the issue. If you want to be formal about it it might be a good opportunity to use a smart constructor.
TAG : haskell
Date : October 18 2020, 08:10 PM , By : Michael Rivera
Filtering by length of lines in file giving unexpected result
Filtering by length of lines in file giving unexpected result
it helps some times The default newline mode for stdin is nativeNewline, which chooses its behavior based on what it believes your OS to be. I suspect that it has (wrongly) decided you are on a Unix system and it therefore should not do CRLF conversi
TAG : haskell
Date : October 18 2020, 08:10 PM , By : Devender Antil
Sharing vs. non-sharing fixed-point combinator
Sharing vs. non-sharing fixed-point combinator
will be helpful for those in need "Sharing" means f x re-uses the x that it creates; but with _Y g = g . g . g . g . ..., each g calculates its output anew (cf. this and this).In that context, the sharing version has much worse memory usage, leads to
TAG : haskell
Date : October 18 2020, 08:10 AM , By : Amy Gracy
What does "ignoring (possibly broken) abi-depends field for packages" mean?
What does "ignoring (possibly broken) abi-depends field for packages" mean?
With these it helps According to this issue https://github.com/haskell/cabal/issues/5465 message appears "whenever a package registration (IPI) includes a abi-depends: field", thought to be redundant and removed in future releases.
TAG : haskell
Date : October 15 2020, 08:10 PM , By : NostalgiaEngineer
What is "proxy a" in printtype function?
What is "proxy a" in printtype function?
it should still fix some issue In general a proxy for a type a is some data type Proxy a whose values carries no information. So the value is passed around to as a witness for its type (for type inference / type checking purposes). In that case proxy
TAG : haskell
Date : October 14 2020, 02:21 PM , By : Lovely Oda
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