Mixing
haskell mocking: define func in datatype with class-constraint
2
there is the function
httpLBS :: MonadIO m => Request -> m (Response ByteString)
in the Network.HTTP.Simple module (doc), which i want to pass around (for mocking later in integration-testing) with my Ctx data-object
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: MonadIO m => Request -> m (Response ByteString)
} deriving (Show)
but I'm getting this error:
Prelude> :l Context.hs
[1 of 1] Compiling Context ( Context.hs, interpreted )
Context.hs:19:32: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Context.hs:19:48: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Failed, no modules loaded.
how is it possible to define this method in my Ctx data-type correctly??
haskell
asked Nov 19 '18 at 12:51
stefa ng
7416
add a comment |
2
there is the function
httpLBS :: MonadIO m => Request -> m (Response ByteString)
in the Network.HTTP.Simple module (doc), which i want to pass around (for mocking later in integration-testing) with my Ctx data-object
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: MonadIO m => Request -> m (Response ByteString)
} deriving (Show)
but I'm getting this error:
Prelude> :l Context.hs
[1 of 1] Compiling Context ( Context.hs, interpreted )
Context.hs:19:32: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Context.hs:19:48: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Failed, no modules loaded.
how is it possible to define this method in my Ctx data-type correctly??
haskell
asked Nov 19 '18 at 12:51
stefa ng
7416
4
Ctx need parameter like: data Ctx m = Ctx {...}
– assembly.jc
Nov 19 '18 at 13:32
ok, so you mean: data Ctx m = Ctx { token :: String, httpLBSFunc :: m } ? but then i have to specify the Ctx type everywhere with "Ctx MonadIO (Response ByteString)" ... right? i wouldn't like that. can't i put that "MonadIO (Response ByteString)" constraint somewhere inside the type?
– stefa ng
Nov 19 '18 at 15:35
1
If you want put the constraint in Constructor, considers to use GADTs instead. Or, put constraint on data type like: data MonadIO m => Ctx m = {...} with enable -XDatatypeContexts language extension,it has been deprecated, but you can still use it.
– assembly.jc
Nov 19 '18 at 16:01
add a comment |
2
2
2
there is the function
httpLBS :: MonadIO m => Request -> m (Response ByteString)
in the Network.HTTP.Simple module (doc), which i want to pass around (for mocking later in integration-testing) with my Ctx data-object
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: MonadIO m => Request -> m (Response ByteString)
} deriving (Show)
but I'm getting this error:
Prelude> :l Context.hs
[1 of 1] Compiling Context ( Context.hs, interpreted )
Context.hs:19:32: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Context.hs:19:48: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Failed, no modules loaded.
how is it possible to define this method in my Ctx data-type correctly??
haskell
asked Nov 19 '18 at 12:51
stefa ng
7416
there is the function
httpLBS :: MonadIO m => Request -> m (Response ByteString)
in the Network.HTTP.Simple module (doc), which i want to pass around (for mocking later in integration-testing) with my Ctx data-object
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: MonadIO m => Request -> m (Response ByteString)
} deriving (Show)
but I'm getting this error:
Prelude> :l Context.hs
[1 of 1] Compiling Context ( Context.hs, interpreted )
Context.hs:19:32: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Context.hs:19:48: error: Not in scope: type variable ‘m’
|
19 | httpLBSFunc :: MonadIO m => Request -> m (Response B.ByteString)
| ^
Failed, no modules loaded.
how is it possible to define this method in my Ctx data-type correctly??
haskell
haskell
asked Nov 19 '18 at 12:51
stefa ng
7416
asked Nov 19 '18 at 12:51
stefa ng
7416
asked Nov 19 '18 at 12:51
stefa ng
7416
asked Nov 19 '18 at 12:51
stefa ng
7416
asked Nov 19 '18 at 12:51
stefa ng
7416
7416
4
Ctx need parameter like: data Ctx m = Ctx {...}
– assembly.jc
Nov 19 '18 at 13:32
ok, so you mean: data Ctx m = Ctx { token :: String, httpLBSFunc :: m } ? but then i have to specify the Ctx type everywhere with "Ctx MonadIO (Response ByteString)" ... right? i wouldn't like that. can't i put that "MonadIO (Response ByteString)" constraint somewhere inside the type?
– stefa ng
Nov 19 '18 at 15:35
1
If you want put the constraint in Constructor, considers to use GADTs instead. Or, put constraint on data type like: data MonadIO m => Ctx m = {...} with enable -XDatatypeContexts language extension,it has been deprecated, but you can still use it.
– assembly.jc
Nov 19 '18 at 16:01
add a comment |
4
Ctx need parameter like: data Ctx m = Ctx {...}
– assembly.jc
Nov 19 '18 at 13:32
ok, so you mean: data Ctx m = Ctx { token :: String, httpLBSFunc :: m } ? but then i have to specify the Ctx type everywhere with "Ctx MonadIO (Response ByteString)" ... right? i wouldn't like that. can't i put that "MonadIO (Response ByteString)" constraint somewhere inside the type?
– stefa ng
Nov 19 '18 at 15:35
1
If you want put the constraint in Constructor, considers to use GADTs instead. Or, put constraint on data type like: data MonadIO m => Ctx m = {...} with enable -XDatatypeContexts language extension,it has been deprecated, but you can still use it.
– assembly.jc
Nov 19 '18 at 16:01
4
4
Ctx need parameter like: data Ctx m = Ctx {...}
– assembly.jc
Nov 19 '18 at 13:32
Ctx need parameter like: data Ctx m = Ctx {...}
– assembly.jc
Nov 19 '18 at 13:32
ok, so you mean: data Ctx m = Ctx { token :: String, httpLBSFunc :: m } ? but then i have to specify the Ctx type everywhere with "Ctx MonadIO (Response ByteString)" ... right? i wouldn't like that. can't i put that "MonadIO (Response ByteString)" constraint somewhere inside the type?
– stefa ng
Nov 19 '18 at 15:35
ok, so you mean: data Ctx m = Ctx { token :: String, httpLBSFunc :: m } ? but then i have to specify the Ctx type everywhere with "Ctx MonadIO (Response ByteString)" ... right? i wouldn't like that. can't i put that "MonadIO (Response ByteString)" constraint somewhere inside the type?
– stefa ng
Nov 19 '18 at 15:35
1
1
If you want put the constraint in Constructor, considers to use GADTs instead. Or, put constraint on data type like: data MonadIO m => Ctx m = {...} with enable -XDatatypeContexts language extension,it has been deprecated, but you can still use it.
– assembly.jc
Nov 19 '18 at 16:01
If you want put the constraint in Constructor, considers to use GADTs instead. Or, put constraint on data type like: data MonadIO m => Ctx m = {...} with enable -XDatatypeContexts language extension,it has been deprecated, but you can still use it.
– assembly.jc
Nov 19 '18 at 16:01
add a comment |
1 Answer
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i don't what the drawbacks are by replacing the constraint MonadIO with the actual Monad IO but for me it was sufficient to get it running:
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: Request -> IO (Response ByteString)
} deriving (Show)
i dont even get the exact difference between them
answered Nov 19 '18 at 17:34
stefa ng
7416
add a comment |
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0
i don't what the drawbacks are by replacing the constraint MonadIO with the actual Monad IO but for me it was sufficient to get it running:
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: Request -> IO (Response ByteString)
} deriving (Show)
i dont even get the exact difference between them
answered Nov 19 '18 at 17:34
stefa ng
7416
add a comment |
0
i don't what the drawbacks are by replacing the constraint MonadIO with the actual Monad IO but for me it was sufficient to get it running:
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: Request -> IO (Response ByteString)
} deriving (Show)
i dont even get the exact difference between them
answered Nov 19 '18 at 17:34
stefa ng
7416
add a comment |
0
0
0
i don't what the drawbacks are by replacing the constraint MonadIO with the actual Monad IO but for me it was sufficient to get it running:
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: Request -> IO (Response ByteString)
} deriving (Show)
i dont even get the exact difference between them
answered Nov 19 '18 at 17:34
stefa ng
7416
i don't what the drawbacks are by replacing the constraint MonadIO with the actual Monad IO but for me it was sufficient to get it running:
data Ctx =
Ctx {
token :: String,
httpLBSFunc :: Request -> IO (Response ByteString)
} deriving (Show)
i dont even get the exact difference between them
answered Nov 19 '18 at 17:34
stefa ng
7416
answered Nov 19 '18 at 17:34
stefa ng
7416
answered Nov 19 '18 at 17:34
stefa ng
7416
answered Nov 19 '18 at 17:34
stefa ng
7416
7416
add a comment |
add a comment |
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4
Ctx need parameter like: data Ctx m = Ctx {...}
– assembly.jc
Nov 19 '18 at 13:32
ok, so you mean: data Ctx m = Ctx { token :: String, httpLBSFunc :: m } ? but then i have to specify the Ctx type everywhere with "Ctx MonadIO (Response ByteString)" ... right? i wouldn't like that. can't i put that "MonadIO (Response ByteString)" constraint somewhere inside the type?
– stefa ng
Nov 19 '18 at 15:35
1
If you want put the constraint in Constructor, considers to use GADTs instead. Or, put constraint on data type like: data MonadIO m => Ctx m = {...} with enable -XDatatypeContexts language extension,it has been deprecated, but you can still use it.
– assembly.jc
Nov 19 '18 at 16:01