Tags down

Home » haskell


Filtering odd length strings from a list of strings
To fix this issue The reason this produces an error is because the filter (…) xs expression will return a list fo strings, not a single string. But your type signature specifies:
TAG :haskell
Date : August 11 2020, 04:00 AM , By : R S
Records with different fields modelling same logical type
I hope this helps you . If Bigshould contain everything that's also contained in Small, it may be viable to make Small a field of Big:
TAG :haskell
Date : August 10 2020, 12:00 PM , By : marina
Avoid impossible states with a data model for a card game in Haskell
seems to work fine There is temptation to have the type checker prove your program is perfect. However, that will become an endless pursuit. There really are not the hours in the day to spend teaching a computer how to be sure what you're sure is sur
TAG :haskell
Date : August 09 2020, 11:00 AM , By : Ajay Shanker
How to write length function for all Monoids
it should still fix some issue A monoid, in the general case, as no notion of length. Take for instance Sum Int, which is Int equipped with addition for its monoidal operation. We have
TAG :haskell
Date : August 08 2020, 08:00 PM , By : mukhtarProgrammer
newtype-like operational semantics for a GADT where the type fully determines the constructor
should help you out This looks impossible to achieve, at least with current GHC. Assume your Payload A had the same representation of Int, and so on.
TAG :haskell
Date : August 08 2020, 03:00 PM , By : akshaya ravikkumar
Make Postgresql.Simple query results available to rest of .hs file
will be helpful for those in need No need to muddy the waters with a database example. How do you pass values from one function to another in Haskell regardless of their source? You pass the value as an argument in a function call. Consider:
TAG :haskell
Date : August 08 2020, 06:26 AM , By : SUSHOBHAN CHAKRABART
How to "rearrange" an Aeson.Object using lenses?
will be helpful for those in need Using lenses from the lens-aeson package, I guess what you want is something like:
TAG :haskell
Date : August 07 2020, 05:00 PM , By : Rony Arifiandy
Pattern matching with Alternative empty or Applicative pure
should help you out I know it is possible, to pattern match against (named) constructors like so: , The best you can do is:
TAG :haskell
Date : August 07 2020, 05:00 AM , By : EswarRaj_ER
Text data in Haskell
around this issue I am really confused with this Text data in Haskell. Can someone explain me what values it has, where can it be used and what actually is the difference between it and a normal String. Thank you in advance. , A String is a list of C
TAG :haskell
Date : August 07 2020, 04:00 AM , By : Welington Orlandi
Type-level induction on KnownNats: Overlapping instances
wish helps you I think the problem is that GHC doesn't know that (1+d) is not 0 for any d.
TAG :haskell
Date : August 06 2020, 06:00 PM , By : Antonio Jiménez Ruiz
Stuck with "Configurable" haskell class
seems to work fine As @luqui points out in the comments, the instance selection process does not work in the way you assume.Because of the signature of gunfold is has a higher-rank forall, the argument to configure is an existential type - and the co
TAG :haskell
Date : August 05 2020, 03:00 PM , By : Davide Valerio
Parsing user input string to UTCTime type
wish helps you I have one general comment, that you are biting off a large chunk of functionality with this approach, and, as you suggested, it is greatly over-engineered. You should not provide the seconds value when it is not present in the source.
TAG :haskell
Date : August 05 2020, 04:00 AM , By : jimbotux
Writing a map for this Monad transformer
this one helps. According to standard rules for determining co/contravariance, "a position is covariant if it is on the left side of an even number of arrows applying to it.". By examining the signature of ChoiceT we see the m parameter occurring in
TAG :haskell
Date : August 05 2020, 12:00 AM , By : Smokin'Joe
How to make a list out of all second elements of a tuple in haskell
wish of those help You can do this by running map snd [(1,"A"),(2,"B"),(3,"C")]. The map function is defined to apply the function given as its second argument to each element of the list given as its third argument; the snd function gets the second
TAG :haskell
Date : August 04 2020, 08:00 PM , By : Renato Gabriel
In GHC.Prim, why can pointer operations fail with an unchecked exception?
I wish this helpful for you Found the answer in the GHC source code: https://github.com/ghc/ghc/blob/master/compiler/prelude/primops.txt.ppL3199-L3233It turns out that it cannot throw an exception but the function is marked as throwing so that GHC wo
TAG :haskell
Date : August 04 2020, 06:00 AM , By : PMooney
How can I express this Constraint?
fixed the issue. Will look into that further I would like to express a Constraint on types of kind k -> k -> Type, which can be stated in English as: , This works:
TAG :haskell
Date : August 04 2020, 05:00 AM , By : Leonid Brish
How to use "BinaryString.uncons()" but with a type distinct from Word8?
Does that help There are many deserialization libraries available. For one that sounds like it is a particularly close match to your mental model, check out binary's Get. It is not really in scope to give a Big List of all the available ones, but a q
TAG :haskell
Date : August 02 2020, 08:00 AM , By : tommyboywonder
Convert Maybe String to (Maybe?) Integer
I think the issue was by ths following , Use Text.Read.readMaybe
TAG :haskell
Date : August 01 2020, 05:00 AM , By : Artem Valiulin
Haskell - Automatic Monad instance
I wish this help you I'm trying to create my own data type, which will be part of Monad class, but , It works fine for other classes (Show for example)
TAG :haskell
Date : July 31 2020, 09:00 AM , By : Fallon Blaser
Implement a self-reference/pointer in a pure/functional language (Elm/Haskell)
hope this fix your issue A binding construct in which the expressions can see the bindings doesn't require any exotic self-reference mechanisms.How it works is that an environment is created for the variables, and then the values are assigned to them
TAG :haskell
Date : July 31 2020, 12:00 AM , By : Nick Gatto
Why don't we write haskell in LISP syntax? (we can!)
like below fixes the issue The syntax of Haskell is historically derived from that of ISWIM, a language which appeared not much later than LISP and which is described in Peter J. Landin's 1966 article The Next 700 Programming Languages. Section 6 is
TAG :haskell
Date : July 30 2020, 12:00 PM , By : Weiheng Lee
Privacy Policy - Terms - Contact Us © voile276.org