Relude.Debug

Functions for debugging. If you left these functions in your code then a warning is generated to remind you about left usages. Also some functions (and data types) are convenient for prototyping.

Use these functions only for debugging purposes. They break referential trasparency, they are only useful when you want to observe intermediate values of your pure functions.

Tracing

trace :: String -> a -> a

Warning: trace remains in code

Version of trace that leaves warning.

>>> increment l = map (+1) l
>>> increment [2, 3, 4]
[3,4,5]

>>> increment l = trace ("incrementing each value of: " ++ show l) (map (+1) l)
>>> increment [2, 3, 4]
incrementing each value of: [2,3,4]
[3,4,5]

traceM :: Applicative f => String -> f ()

Warning: traceM remains in code

Version of traceM that leaves warning.

>>> :{
let action :: Maybe Int
    action = do
        x <- Just 3
        traceM ("x: " ++ show x)
        y <- pure 12
        traceM ("y: " ++ show y)
        pure (x*2 + y)
in action
:}
x: 3
y: 12
Just 18

traceId :: String -> String

Warning: traceId remains in code

Version of traceId that leaves warning.

>>> traceId "hello"
"hello
hello"

traceShow :: Show a => a -> b -> b

Warning: traceShow remains in code

Version of traceShow that leaves warning.

>>> increment l = map (+1) l
>>> increment [2, 3, 4]
[3,4,5]

>>> increment l = traceShow l (map (+1) l)
>>> increment [2, 3, 4]
[2,3,4]
[3,4,5]

traceShowId :: Show a => a -> a

Warning: traceShowId remains in code

Version of traceShowId that leaves warning.

>>> traceShowId (1+2+3, "hello" ++ "world")
(6,"helloworld")
(6,"helloworld")

traceShowM :: (Show a, Applicative f) => a -> f ()

Warning: traceShowM remains in code

Like traceM, but uses show on the argument to convert it to a String.

>>> :{
let action :: Maybe Int
    action = do
        x <- Just 3
        traceShowM x
        y <- pure 12
        traceShowM y
        pure (x*2 + y)
in action
:}
3
12
Just 18

Imprecise error

error :: forall (r :: RuntimeRep) (a :: TYPE r) (t :: Type). (HasCallStack, IsText t) => t -> a

Throw pure errors. Use this function only to when you are sure that this branch of code execution is not possible. DO NOT USE error as a normal error handling mechanism.

>>> error "oops"
*** Exception: oops
CallStack (from HasCallStack):
  error, called at src/Relude/Debug.hs:204:11 in ...
...

⚠️CAUTION⚠️ Unlike Prelude version, error takes Text as an argument. In case it used by mistake, the user will see the following:

>>> error ("oops" :: String)
...
... 'error' expects 'Text' but was given 'String'.
      Possible fixes:
          * Make sure OverloadedStrings extension is enabled
          * Use 'error (toText msg)' instead of 'error msg'
...
>>> error False
...
... 'error' works with 'Text'
      But given: Bool
...

data Undefined

Warning: Undefined type remains in code

Similar to undefined but data type.

Constructors

Undefined

Warning: Undefined type remains in code

Instances

Bounded Undefined

Defined in Relude.Debug

Methods

minBound :: Undefined

maxBound :: Undefined

Enum Undefined

Defined in Relude.Debug

Methods

succ :: Undefined -> Undefined

pred :: Undefined -> Undefined

toEnum :: Int -> Undefined

fromEnum :: Undefined -> Int

enumFrom :: Undefined -> [Undefined]

enumFromThen :: Undefined -> Undefined -> [Undefined]

enumFromTo :: Undefined -> Undefined -> [Undefined]

enumFromThenTo :: Undefined -> Undefined -> Undefined -> [Undefined]

Eq Undefined

Defined in Relude.Debug

Methods

(==) :: Undefined -> Undefined -> Bool

(/=) :: Undefined -> Undefined -> Bool

Data Undefined

Defined in Relude.Debug

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Undefined -> c Undefined

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Undefined

toConstr :: Undefined -> Constr

dataTypeOf :: Undefined -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Undefined)

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Undefined)

gmapT :: (forall b. Data b => b -> b) -> Undefined -> Undefined

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Undefined -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Undefined -> r

gmapQ :: (forall d. Data d => d -> u) -> Undefined -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> Undefined -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Undefined -> m Undefined

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Undefined -> m Undefined

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Undefined -> m Undefined

Ord Undefined

Defined in Relude.Debug

Methods

compare :: Undefined -> Undefined -> Ordering

(<) :: Undefined -> Undefined -> Bool

(<=) :: Undefined -> Undefined -> Bool

(>) :: Undefined -> Undefined -> Bool

(>=) :: Undefined -> Undefined -> Bool

max :: Undefined -> Undefined -> Undefined

min :: Undefined -> Undefined -> Undefined

Read Undefined

Defined in Relude.Debug

Methods

readsPrec :: Int -> ReadS Undefined

readList :: ReadS [Undefined]

readPrec :: ReadPrec Undefined

readListPrec :: ReadPrec [Undefined]

Show Undefined

Defined in Relude.Debug

Methods

showsPrec :: Int -> Undefined -> ShowS

show :: Undefined -> String

showList :: [Undefined] -> ShowS

Generic Undefined

Defined in Relude.Debug

Associated Types

type Rep Undefined :: Type -> Type

Methods

from :: Undefined -> Rep Undefined x

to :: Rep Undefined x -> Undefined

type Rep Undefined

Defined in Relude.Debug

type Rep Undefined = D1 ('MetaData "Undefined" "Relude.Debug" "relude-0.6.0.0-inplace" 'False) (C1 ('MetaCons "Undefined" 'PrefixI 'False) (U1 :: Type -> Type))

undefined :: forall (r :: RuntimeRep). forall (a :: TYPE r). HasCallStack => a

Warning: undefined function remains in code

undefined that leaves warning in code on every usage.