semigroup Questions
3
Solved
I am a Haskell newbie and I wonder why there is no alternative instance for Either but a semigroup, which behaves as I would expect it from alternative:
instance Semigroup (Either a b) where
Left ...
Maidstone asked 10/6, 2017 at 10:1
2
What's the simplest yet most elegant way to NOT short-circuit and instead collect errors until their values are used?
What's so hard in accumulating errors? Short circuit only if a function call re...
Polytrophic asked 11/3 at 11:55
1
Solved
Is there any newtype in base that would basically achieve the following?
newtype SemigroupFlip a = SemigroupFlip a
instance Semigroup a => Semigroup (SemigroupFlip a) where
(SemigroupFlip a) &...
3
Solved
The base library in Haskell has the following type synonyms in Data.Semigroup:
type ArgMin a b = Min (Arg a b)
type ArgMax a b = Max (Arg a b)
Here are links to the haddocks: ArgMin and ArgMax
W...
Nutritionist asked 20/11, 2020 at 12:54
2
Given an operation (??) such that
(a ?? b) ?? c = a ?? (b ?? c)
(that is to say (??) is associative)
must it be the case that
liftA2 (??) (liftA2 (??) a b) c = liftA2 (??) a (liftA2 (??) b c)
...
Ceaseless asked 27/5, 2020 at 6:44
1
Solved
Using cats.Semigroup one can write this:
import cats.Semigroup
import cats.implicits._
val l1: String Either Int = Left("error")
val r1: String Either Int = Right(1)
val r2: String Either Int = R...
Coelacanth asked 14/3, 2019 at 14:11
2
Maybe expresses computations that might not produce a result due to an error. Therefore such computations must be short circuited.
Now Maybe's Semigroup/Monoid instances seem to break with this se...
Waldgrave asked 4/5, 2018 at 8:36
2
Solved
I may have been under the false impression that Haskell is lazier than it is, but I wonder if there's a way to get the best of both worlds...
Data.Monoid and Data.Semigroup define two variations o...
Pless asked 5/11, 2017 at 10:13
0
Trying to learn Haskell and stumbled upon this:
Prelude> import Data.Semigroup
Prelude Data.Semigroup> let x = Sum 0.1 <> Sum 0.2 <> Sum 0.3
Prelude Data.Semigroup> let y = (S...
2
Solved
I'm trying to make a Semigroup and VerifiedSemigroup instance on my custom Bool datatype both on operator && and operator ||:
%case data Lógico = Cierto | Falso
(&&) : Lógico ->...
Astolat asked 1/2, 2015 at 20:42
2
Solved
This is the pseudocode for the radix sort:
Pseudocode for Radix Sort:
Radix-Sort(A, d)
// Each key in A[1..n] is a d-digit integer. (Digits are
// numbered 1 to d from right to left.)
1. for i = 1...
1
Solved
Number of binary operation on a set of 2 elements is 2^(2*2)=16.
Number of associative binary operation on that set is only 8.
Number of binary operation on a set of 3 elements is 3^(3*3)=19683....
Combination asked 9/7, 2014 at 16:25
1
Solved
Given the following pseudocode for the bubble-sort
procedure bubbleSort( A : list of sortable items )
repeat
swapped = false
for i = 1 to length(A) - 1 inclusive do:
/* if this pair is out of...
1
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