Trying to install persistent with etlas.
$ etlas install persistent
I get the following error:
src/Language/Haskell/TH/Instances.hs:360:29: error:
Could not deduce (transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
t58)
arising from a use of ‘MTL.lift’
from the context (Applicative (ReaderT r m),
Monad (ReaderT r m),
Quasi m)
bound by the instance declaration
at src/Language/Haskell/TH/Instances.hs:358:1039
The type variable ‘t58’ is ambiguous
Note: there are several potential instances:
instance [safe] transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
(transformers0.5.5.0:Control.Monad.Trans.Error.ErrorT e)
 Defined in ‘transformers0.5.5.0:Control.Monad.Trans.Error’
instance [safe] Monoid w =>
transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
(RWST r w s)
 Defined in ‘transformers0.5.5.0:Control.Monad.Trans.RWS.Lazy’
instance [safe] transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
(ReaderT r)
 Defined in ‘transformers0.5.5.0:Control.Monad.Trans.Reader’
...plus two others
In the expression: MTL.lift
In the expression: MTL.lift $ qReport a b
In an equation for ‘qReport’: qReport a b = MTL.lift $ qReport a b

360  qReport a b = MTL.lift $ qReport a b
 ^^^^^^^^
Anybody know what this is about?
$ etlas install persistent
I get the following error:
src/Language/Haskell/TH/Instances.hs:360:29: error:
Could not deduce (transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
t58)
arising from a use of ‘MTL.lift’
from the context (Applicative (ReaderT r m),
Monad (ReaderT r m),
Quasi m)
bound by the instance declaration
at src/Language/Haskell/TH/Instances.hs:358:1039
The type variable ‘t58’ is ambiguous
Note: there are several potential instances:
instance [safe] transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
(transformers0.5.5.0:Control.Monad.Trans.Error.ErrorT e)
 Defined in ‘transformers0.5.5.0:Control.Monad.Trans.Error’
instance [safe] Monoid w =>
transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
(RWST r w s)
 Defined in ‘transformers0.5.5.0:Control.Monad.Trans.RWS.Lazy’
instance [safe] transformers0.5.5.0:Control.Monad.Trans.Class.MonadTrans
(ReaderT r)
 Defined in ‘transformers0.5.5.0:Control.Monad.Trans.Reader’
...plus two others
In the expression: MTL.lift
In the expression: MTL.lift $ qReport a b
In an equation for ‘qReport’: qReport a b = MTL.lift $ qReport a b

360  qReport a b = MTL.lift $ qReport a b
 ^^^^^^^^
Anybody know what this is about?
Post has attachment
For beginners: How do functional languages work?
Very nice talk, highly recommended to get the building blocks of "functional" right.
Very nice talk, highly recommended to get the building blocks of "functional" right.
Post has shared content
Yay, Haskell!
SPJ signing my friends notebook.
And the blue knees on the right: that's me.
SPJ signing my friends notebook.
And the blue knees on the right: that's me.
What is the exact relationship between Haskell monads and monads in the sense of Category Theory ?
Let C be a concrete category and T a monad on X. Then for any two objects A and B of X we can define a map:
bind_AB: T(A) X Hom(A, TB)> T(B) (we are Currying)
For let x be in T(A) and f in Hom(A,TB) and m: TT> T the monad "multiplication".
then we can define bind_AB(x) = m_B(T(f)(x))
recall that m_B is a morphism: T(T(B)) > T(B)
let ret_A: A > T(A) be the unit of the monad.
then we can picture the Kleisli category of T and the
composition f o g of
f: A > T(B) and g: B > T(C) as being given by
bind_BC(_,g) o f
ret_A is the identity morphism for this composition.
It remains to show that conversely given a Haskell monad we can define a categorytheory monad.
Let C be a concrete category and T a monad on X. Then for any two objects A and B of X we can define a map:
bind_AB: T(A) X Hom(A, TB)
For let x be in T(A) and f in Hom(A,TB) and m: TT> T the monad "multiplication".
then we can define bind_AB(x) = m_B(T(f)(x))
recall that m_B is a morphism: T(T(B)) > T(B)
let ret_A: A > T(A) be the unit of the monad.
then we can picture the Kleisli category of T and the
composition f o g of
f: A > T(B) and g: B > T(C) as being given by
bind_BC(_,g) o f
ret_A is the identity morphism for this composition.
It remains to show that conversely given a Haskell monad we can define a categorytheory monad.
Post has attachment
Awesome new role with IOHK for a Community Manager
I'm brand new to Haskell and using an archived EDX course (FP101) with the "Programming in Haskell" book. What I can't seem to find is something like a quick reference to the builtin functions. This would help a lot. I seem to regularly get to a point where I'm sure there's a function available already to do something basic, but I can't find it:(
Any suggies?
Thanx  Charlie
Any suggies?
Thanx  Charlie
Post has attachment
Hey All,
I am currently working with an awesome blockchain company based in New York who are on the search for talented and experienced Haskell engineers to join the team. Paying up to $180,000 + Benefits + Coins!
Sound like something that could be of interest? Check it out  https://bit.ly/2K3JVVy
I am currently working with an awesome blockchain company based in New York who are on the search for talented and experienced Haskell engineers to join the team. Paying up to $180,000 + Benefits + Coins!
Sound like something that could be of interest? Check it out  https://bit.ly/2K3JVVy
Post has attachment
I'm happy to announce a new release of the z3 package, version 4.3, the unofficial Haskell bindings to Microsoft's Z3 API.
Changelog here: https://github.com/IagoAbal/haskellz3/blob/master/CHANGES.md.
By the way, after many requests I have moved the repository to GitHub: https://github.com/IagoAbal/haskellz3.
Changelog here: https://github.com/IagoAbal/haskellz3/blob/master/CHANGES.md.
By the way, after many requests I have moved the repository to GitHub: https://github.com/IagoAbal/haskellz3.
how to get haskell code execution time (runtime)?
Sorry for my english, I'm brazilian.
I need to know the Real Time, Sys Time and user time (execution) of some codes haskell.
Sorry for my english, I'm brazilian.
I need to know the Real Time, Sys Time and user time (execution) of some codes haskell.
Post has attachment
New release of bv, a Haskell library for bitvector arithmetic.
Wait while more posts are being loaded