| Copyright | (c) Justin Le 2019 |
|---|---|
| License | BSD3 |
| Maintainer | justin@jle.im |
| Stability | experimental |
| Portability | non-portable |
| Safe Haskell | None |
| Language | Haskell2010 |
GHC.TypeLits.Printf.Internal
Description
Internal workings of the printf mechanisms, exposed for potential debugging purposes.
Please do not use this module for anything besides debugging, as is definitely very unstable and might go away or change dramatically between versions.
Synopsis
- type ParseFmtStr str = EvalParser FmtStrParser str
- type ParseFmtStr_ str = EvalParser_ FmtStrParser str
- type ParseFmt str = EvalParser FFParser str
- type ParseFmt_ str = EvalParser_ FFParser str
- data FormatAdjustment
- type family ShowFormat (x :: k) :: Symbol
- data FormatSign
- data WidthMod
- data Flags = Flags {}
- type EmptyFlags = 'Flags 'Nothing 'Nothing 'False
- data FieldFormat = FF {}
- type SChar = Symbol
- type family Demote k = a | a -> k
- class Reflect (x :: a) where
- class FormatType (t :: SChar) a where
- formatArg :: p t -> a -> FieldFormat -> ShowS
- class Printf (str :: Symbol) fun where
- printf_ :: p str -> fun
- class FormatFun (ffs :: [Either Symbol FieldFormat]) fun where
- newtype PFmt c = PFmt FieldFormat
- pfmt :: forall c a. FormatType c a => PFmt c -> a -> String
- mkPFmt :: forall str lst ff f w q m c. (Listify str lst, ff ~ ParseFmt_ lst, Reflect ff, ff ~ 'FF f w q m c) => PFmt c
- mkPFmt_ :: forall str lst ff f w q m c p. (Listify str lst, ff ~ ParseFmt_ lst, Reflect ff, ff ~ 'FF f w q m c) => p str -> PFmt c
- newtype PHelp = PHelp {}
Documentation
type ParseFmtStr str = EvalParser FmtStrParser str Source #
type ParseFmtStr_ str = EvalParser_ FmtStrParser str Source #
data FormatAdjustment #
Whether to left-adjust or zero-pad a field. These are
mutually exclusive, with LeftAdjust taking precedence.
Since: base-4.7.0.0
Constructors
| LeftAdjust | |
| ZeroPad |
Instances
| Reflect 'ZeroPad Source # | |
| Reflect 'LeftAdjust Source # | |
Defined in GHC.TypeLits.Printf.Parse Methods reflect :: p 'LeftAdjust -> Demote a Source # | |
| type Demote FormatAdjustment Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'ZeroPad Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'LeftAdjust Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
type family ShowFormat (x :: k) :: Symbol Source #
Instances
data FormatSign #
How to handle the sign of a numeric field. These are
mutually exclusive, with SignPlus taking precedence.
Since: base-4.7.0.0
Instances
| Reflect 'SignSpace Source # | |
| Reflect 'SignPlus Source # | |
| type Demote FormatSign Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'SignSpace Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'SignPlus Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
Instances
| Reflect 'WMhh Source # | |
| Reflect 'WMh Source # | |
| Reflect 'WMl Source # | |
| Reflect 'WMll Source # | |
| Reflect 'WML Source # | |
| type Demote WidthMod Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'WMhh Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'WMh Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'WMl Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'WMll Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat 'WML Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
Constructors
| Flags | |
Fields
| |
Instances
| (Reflect d, Reflect i, Reflect l) => Reflect ('Flags d i l :: Flags) Source # | |
| type Demote Flags Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type ShowFormat ('Flags a s 'True :: Flags) Source # | |
Defined in GHC.TypeLits.Printf.Parse type ShowFormat ('Flags a s 'True :: Flags) = AppendSymbol (AppendSymbol (ShowFormat a) (ShowFormat s)) "#" | |
| type ShowFormat ('Flags a s 'False :: Flags) Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
data FieldFormat Source #
Constructors
| FF | |
Instances
type family Demote k = a | a -> k Source #
Instances
| type Demote Bool Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote Nat Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote Symbol Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote FormatAdjustment Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote FormatSign Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote FieldFormat Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote WidthMod Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote Flags Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| type Demote (Maybe a) Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
class Reflect (x :: a) where Source #
Instances
| Reflect 'False Source # | |
| Reflect 'True Source # | |
| KnownNat n => Reflect (n :: Nat) Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| KnownSymbol n => Reflect (n :: Symbol) Source # | |
Defined in GHC.TypeLits.Printf.Parse | |
| Reflect 'ZeroPad Source # | |
| Reflect 'LeftAdjust Source # | |
Defined in GHC.TypeLits.Printf.Parse Methods reflect :: p 'LeftAdjust -> Demote a Source # | |
| Reflect 'SignSpace Source # | |
| Reflect 'SignPlus Source # | |
| Reflect 'WMhh Source # | |
| Reflect 'WMh Source # | |
| Reflect 'WMl Source # | |
| Reflect 'WMll Source # | |
| Reflect 'WML Source # | |
| (Reflect d, Reflect i, Reflect l) => Reflect ('Flags d i l :: Flags) Source # | |
| (Reflect flags, Reflect width, Reflect prec, Reflect mods, Reflect chr) => Reflect ('FF flags width prec mods chr :: FieldFormat) Source # | |
| Reflect ('Nothing :: Maybe a) Source # | |
| Reflect x => Reflect ('Just x :: Maybe a) Source # | |
class FormatType (t :: SChar) a where Source #
Typeclass associating format types (d, f, etc.) with the types
that can be formatted by them.
You can extend the printf methods here for your own types by writing your instances here.
Minimal complete definition
Nothing
Methods
formatArg :: p t -> a -> FieldFormat -> ShowS Source #
Instances
class Printf (str :: Symbol) fun where Source #
Methods
printf_ :: p str -> fun Source #
A version of printf taking an explicit
proxy, which allows usage without TypeApplications
>>>putStrLn $ printf_ (Proxy :: Proxy "You have %.2f dollars, %s") 3.62 "Luigi"You have 3.62 dollars, Luigi
Instances
| (Listify str lst, ffs ~ ParseFmtStr_ lst, FormatFun ffs fun) => Printf str fun Source # | |
Defined in GHC.TypeLits.Printf.Internal | |
class FormatFun (ffs :: [Either Symbol FieldFormat]) fun where Source #
The typeclass supporting polyarity used by
printf. It works in mostly the same way as
PrintfType from Text.Printf, and similar the same as
FormatF. Ideally, you will never have to
run into this typeclass or have to deal with it directly.
Every item in the first argument of FormatFun is a chunk of the
formatting string, split between format holes (Right) and string
chunks (Left).
If you want to see some useful error messages for feedback, pHelp can
be useful:
>>>pHelp $ printf @"You have %.2f dollars, %s" 3.62-- ERROR: Call to printf missing argument fulfilling "%s" -- Either provide an argument or rewrite the format string to not expect -- one.
Instances
| (TypeError ('Text "Result type of a call to printf not sufficiently inferred." :$$: 'Text "Please provide an explicit type annotation or other way to help inference.") :: Constraint) => FormatFun ('[] :: [Either Symbol FieldFormat]) () Source # | |
Defined in GHC.TypeLits.Printf.Internal | |
| a ~ String => FormatFun ('[] :: [Either Symbol FieldFormat]) a Source # | |
Defined in GHC.TypeLits.Printf.Internal | |
| a ~ Char => FormatFun ('[] :: [Either Symbol FieldFormat]) Text Source # | |
| a ~ Char => FormatFun ('[] :: [Either Symbol FieldFormat]) Text Source # | |
| a ~ Char => FormatFun ('[] :: [Either Symbol FieldFormat]) PHelp Source # | |
| a ~ () => FormatFun ('[] :: [Either Symbol FieldFormat]) (IO a) Source # | |
| (TypeError ((('Text "An extra argument of type " :<>: 'ShowType a) :<>: 'Text " was given to a call to printf.") :$$: 'Text "Either remove the argument, or rewrite the format string to include the appropriate hole") :: Constraint) => FormatFun ('[] :: [Either Symbol FieldFormat]) (a -> b) Source # | |
Defined in GHC.TypeLits.Printf.Internal | |
| (KnownSymbol str, FormatFun ffs fun) => FormatFun (('Left str :: Either Symbol FieldFormat) ': ffs) fun Source # | |
| (TypeError (MissingError ff) :: Constraint) => FormatFun (('Right ff :: Either Symbol FieldFormat) ': ffs) PHelp Source # | |
| (TypeError (MissingError ff) :: Constraint) => FormatFun (('Right ff :: Either Symbol FieldFormat) ': ffs) Text Source # | |
| (TypeError (MissingError ff) :: Constraint) => FormatFun (('Right ff :: Either Symbol FieldFormat) ': ffs) Text Source # | |
| (TypeError (MissingError ff) :: Constraint) => FormatFun (('Right ff :: Either Symbol FieldFormat) ': ffs) () Source # | |
| (TypeError (MissingError ff) :: Constraint) => FormatFun (('Right ff :: Either Symbol FieldFormat) ': ffs) String Source # | |
| (afun ~ (arg -> fun), Reflect ff, ff ~ 'FF f w p m c, FormatType c arg, FormatFun ffs fun) => FormatFun (('Right ff :: Either Symbol FieldFormat) ': ffs) afun Source # | |
| (TypeError (MissingError ff) :: Constraint) => FormatFun (('Right ff :: Either Symbol FieldFormat) ': ffs) (IO a) Source # | |
Utility type powering pfmt. See documentation for pfmt for more
information on usage.
Using OverloadedLabels, you never need to construct this directly
can just write #f and a PFmt "f"mkPFmt or mkPFmt_, in the situations where
OverloadedLabels doesn't work or is not wanted.
Constructors
| PFmt FieldFormat |
pfmt :: forall c a. FormatType c a => PFmt c -> a -> String Source #
Parse and run a single format hole on a single vale. Can be useful
for formatting individual items or for testing your own custom instances of
FormatType.
Usually meant to be used with OverloadedLabels:
>>>pfmt #f 3.62"3.62"
However, current versions of GHC disallow labels that aren't valid
identifier names, disallowing things like pfmt #.2f 3.62mkPFmt:
>>>pfmt (mkPFmt @".2f") 3.6234124"3.62"
Ideally we'd want to be able to write
>>>pfmt #.2f 3.6234124"3.62"
(which should be possible in GHC 8.10+)
Note that the format string should not include the leading %.
mkPFmt :: forall str lst ff f w q m c. (Listify str lst, ff ~ ParseFmt_ lst, Reflect ff, ff ~ 'FF f w q m c) => PFmt c Source #
Useful for using pfmt without OverloadedLabels, or also when
passing format specifiers that aren't currently allowed with
OverloadedLabels until GHC 8.10+ (like #.2f).
>>>pfmt (mkPFmt @".2f") 3.6234124"3.62"
mkPFmt_ :: forall str lst ff f w q m c p. (Listify str lst, ff ~ ParseFmt_ lst, Reflect ff, ff ~ 'FF f w q m c) => p str -> PFmt c Source #
A version of mkPFmt that takes an explicit proxy input.
>>>pfmt (mkPFmt_ (Proxy :: Proxy ".2f")) 3.6234124"3.62"
A useful tool for helping the type system give useful errors for
printf:
>>>printf @"You have ".2f" dollars, %s" 3.26 :: PHelp-- ERROR: Call to printf missing argument fulfilling "%s" -- Either provide an argument or rewrite the format string to not expect -- one.
Mostly useful if you want to force a useful type error to help see what is going on.
See also pHelp
Constructors
| PHelp | |
Fields
| |