i´am getting error when i am uploading the file:
contains illegal pragma: {-# OPTIONS_GHC -Wno-incomplete-patterns #-}
why is it wrong?
I am programing an Tree in haskell:
{-# OPTIONS_GHC -Wno-incomplete-patterns #-}
module Tree where
import Test.HUnit
import Data.Char
Related
Quite surprisingly, I'm trying to fix a compilation warning missing-export-lists by adding explicitly the elements imported one by one for a specific module, but somehow there is something magical that this module is implicitly exporting that I can't find....
is it possible to retrieve what is exported implicitly with ghc ?
Here is an example of my issue, Yesod is generating some code with TH and quasiquotes :
{-# LANGUAGE EmptyDataDecls #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
import Control.Monad.IO.Class (liftIO)
import Database.Persist
import Database.Persist.Sqlite
import Database.Persist.TH
share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistLowerCase|
Person
name String
age Int Maybe
deriving Show
|]
Then let's say we use that generated code that way :
people <- selectList
( [PersonAge >. 25, PersonAge <=. 30]
||. [PersonName /<-. ["Adam", "Bonny"]]
||. ([PersonAge ==. 50] ||. [PersonAge ==. 60])
)
[]
liftIO $ print people
Now I want to put share in a specific module and control precisely what I'm exporting from that code generated.
I don't know how it generates PersonName and PersonAge ! I don't how to specifically import these 2 types for example...
I have the following at the top of my Haskell file:
{-# LANGUAGE DeriveGeneric, OverloadedStrings, DefaultSignatures, TypeOperators, FlexibleContexts, RecordWildCards, FlexibleInstances, ExtendedDefaultRules #-}
module Main where
import qualified Data.Map as Map
import qualified Data.Set as Set
import Data.Text (Text)
import Data.DateTime
import Data.Aeson
newtype Price = Price Float deriving Generic
However, when I run:
$ stack ghci
...
Prelude> :l myfile.hs
[1 of 1] Compiling Main ( myfile.hs, interpreted )
myfile.hs:13:38: error:
Not in scope: type constructor or class ‘Generic’
|
13 | newtype Price = Price Float deriving Generic
| ^^^^^^^
Failed, no modules loaded.
It seems to not accept my pragma for generics. What am I doing wrong? Looking at similar questions, this seems like it should work.
You also need to import GHC.Generics:
-- other imports
import GHC.Generics
-- more imports
Is there any way to have as single TH function, define a type, and use the type, as well? Relevant code below. PersonPoly2 is being defined by makeRecordSplice and then being passed to makeAdaptorAndInstance (from Opalaye), which is also a TH function.
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
module Lib where
import Data.Profunctor.Product.TH (makeAdaptorAndInstance)
import Language.Haskell.TH
makeRecordSplice :: Q [Dec]
makeRecordSplice = [d|
data PersonPoly2 a b = Person2
{ id :: a
, name :: b
}
|]
makeRecordAndAdapter :: Q [Dec]
makeRecordAndAdapter = do
record <- makeRecordSplice
adapter <- makeAdaptorAndInstance "pPerson2" (mkName "PersonPoly2")
return $ record ++ adapter
-------------
/home/Projects/scratch/app/Main.hs:26:1: error:
‘PersonPoly2’ is not in scope at a reify
Failed, modules loaded: Lib.
The problem you are having is that makeRecordSplice needs to be in a different module than the one it is instantiated in. This Template-Haskell limitation ensures non-circular dependencies at compile time. It is an annoying limitation but not too difficult to go around. Here is one way you could do it:
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
module Main where
import Data.Profunctor.Product.TH (makeAdaptorAndInstance)
import Language.Haskell.TH
import Lib (makeRecordSplice)
$(makeRecordSplice)
$(makeAdaptorAndInstance "pPerson2" (mkName "PersonPoly2"))
main :: IO ()
main = undefined
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
module Lib where
import Data.Profunctor.Product.TH (makeAdaptorAndInstance)
import Language.Haskell.TH
makeRecordSplice :: Q [Dec]
makeRecordSplice = [d|
data PersonPoly2 a b = Person2
{ id :: a
, name :: b
}
|]
You can obviously create an alias for makeAdaptorAndInstance "pPerson2" (mkName "PersonPoly2") and hide it in Lib, you just can't have a splice dependent on another one in the same module.
Hope this helps! :-)
I'm not sure why I cant get this working....
I have QuasiQuotes and OverloadedStrings at the top of my hs file, at the top of main.hs, maindevel.hs and also declared in my foo.cabal file.
The ERROR:
Couldn't match type ‘[Char]’ with ‘Text’
Expected type: Text
Actual type: String
In the second argument of ‘($)’, namely
‘renderHtml (GHC.Base.id (toHtml y))’
In the expression:
putStrLn $ renderHtml (GHC.Base.id (toHtml y))
Code:
module Widgets.MainWidgets where
{-# LANGUAGE GADTs #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings, TypeSynonymInstances, FlexibleInstances #-}
import Import
import Text.Hamlet (shamlet)
import Text.Blaze.Html.Renderer.String (renderHtml)
import Data.Char (toLower)
import Data.List (sort)
import qualified Data.Text as T
import qualified Data.Text.IO as T
import ClassyPrelude
import Yesod
import Data.Time.Clock
import Data.Time.Calendar
import Data.Time.LocalTime
import Data.Time.Format
getCurrYear :: String
getCurrYear = formatTime defaultTimeLocale "%y" getCurrentTime
getYear :: IO ()
getYear = putStrLn $ renderHtml
[shamlet|#{y}|]
where y = getCurrYear
I also have this in my foo.cabal file:
extensions: TemplateHaskell
QuasiQuotes
OverloadedStrings
NoImplicitPrelude
CPP
MultiParamTypeClasses
TypeFamilies
GADTs
GeneralizedNewtypeDeriving
FlexibleContexts
EmptyDataDecls
NoMonomorphismRestriction
DeriveDataTypeable
ViewPatterns
TupleSections
RecordWildCards
TypeSynonymInstances
FlexibleInstances
DeriveGeneric
Any idea why I get the String/Text conversion error?
Thanks in advance!
Adrian
The putStrLn from ClassyPrelude takes a Text, not a String. The simplest solution would be to change the Renderer import to the Text version of the module.
How do you build a unique key with two or more fields using the persistLowerCase quasiquoter?
When using Database.Persist to create models for a simple website using guidance from the Yesod book, the following error crops up:
Build FAILED
$PREFIX/App/Models.hs: line 42, column 18:
Not in scope: data constructor `GroupSlug'
$PREFIX/App/Models.hs: line 43, column 19:
Not in scope: data constructor `GroupName'
App/Models.hs
{-# LANGUAGE EmptyDataDecls #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
module App.Models where
import Data.Text (Text)
import Database.Persist.TH
share [ mkPersist sqlSettings
, mkMigrate "migrateAll"] [persistLowerCase|
Post
group GroupId
postName Text
postSlug Text
period Text
content_en Text
content_pt Text
UniquePost postSlug
deriving Show
Group
groupId Int
groupName Text
groupSlug Text
parent GroupId
UniqueGroup groupId groupSlug
deriving Show
|]
App/Handlers.hs
{-# LANGUAGE OverloadedStrings #-}
module App.Handlers where
import Database.Esqueleto
import App.Models
groupQuery x =
select $
from $ \g -> do
where_ (g ^. GroupSlug ==. val x)
return $ g ^. GroupName
Versions:
Haskell Platform 2013.2
Cabal == 1.19.2
persistent == 1.3.0.2
scotty == 0.6.2
esqueleto == 1.3.4.5
Am I missing some extension or overlooking something else?
As far as I'm aware, data constructors that you're trying to use are actually called GroupGroupSlug and GroupGroupName (not just GroupSlug and GroupName). That is because the data type is generated by taking the entity name and joining it with the field name (with proper capitalisation). Try loading your source files with the -ddump-splices command-line parameter, and you should see it in the output somewhere.