| Copyright | (c) Erich Gut |
|---|---|
| License | BSD3 |
| Maintainer | zerich.gut@gmail.com |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
OAlg.Data.Show
Description
showing data with some auxiliary functions.
Show
Conversion of values to readable Strings.
Derived instances of Show have the following properties, which
are compatible with derived instances of Read:
- The result of
showis a syntactically correct Haskell expression containing only constants, given the fixity declarations in force at the point where the type is declared. It contains only the constructor names defined in the data type, parentheses, and spaces. When labelled constructor fields are used, braces, commas, field names, and equal signs are also used. - If the constructor is defined to be an infix operator, then
showsPrecwill produce infix applications of the constructor. - the representation will be enclosed in parentheses if the
precedence of the top-level constructor in
xis less thand(associativity is ignored). Thus, ifdis0then the result is never surrounded in parentheses; ifdis11it is always surrounded in parentheses, unless it is an atomic expression. - If the constructor is defined using record syntax, then
showwill produce the record-syntax form, with the fields given in the same order as the original declaration.
For example, given the declarations
infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of Show is equivalent to
instance (Show a) => Show (Tree a) where
showsPrec d (Leaf m) = showParen (d > app_prec) $
showString "Leaf " . showsPrec (app_prec+1) m
where app_prec = 10
showsPrec d (u :^: v) = showParen (d > up_prec) $
showsPrec (up_prec+1) u .
showString " :^: " .
showsPrec (up_prec+1) v
where up_prec = 5Note that right-associativity of :^: is ignored. For example,
show(Leaf 1 :^: Leaf 2 :^: Leaf 3)"Leaf 1 :^: (Leaf 2 :^: Leaf 3)".
Methods
Arguments
| :: Int | the operator precedence of the enclosing
context (a number from |
| -> a | the value to be converted to a |
| -> ShowS |
Convert a value to a readable String.
showsPrec should satisfy the law
showsPrec d x r ++ s == showsPrec d x (r ++ s)
Derived instances of Read and Show satisfy the following:
That is, readsPrec parses the string produced by
showsPrec, and delivers the value that showsPrec started with.
Instances
tween :: a -> [a] -> [a] Source #
inserting the given value in between the elements of the given list.
Examples
>>>tween ',' "12345""1,2,3,4,5"
>>>tween ',' """"
>>>tween ',' "1""1"
jtween :: [a] -> [[a]] -> [a] Source #
inserting the given list in between the elements of the given list and joining the result.
Example
>>>jtween ";" ["abcd","efg"]"abcd;efg"
class Show1 (p :: Type -> Type) where Source #
showable for one parameterized types.
Minimal complete definition
Nothing
class Show2 (h :: Type -> Type -> Type) where Source #
showable for two parameterized types.
Note We use this class mearly in the context of Path.
Minimal complete definition
Nothing
Instances
| Show2 EntEmpty2 Source # | |
| Show2 GLApp Source # | |
| Show2 TrApp Source # | |
| Show2 (Homomorphous m) Source # | |
Defined in OAlg.Category.Definition Methods show2 :: Homomorphous m a b -> String Source # | |
| Show2 h => Show2 (Op2 h) Source # | |
| Show2 m => Show2 (Path m) Source # | |
| Semiring r => Show2 (HomSymbol r) Source # | |
| Show2 (SliceFactorDrop s) Source # | |
Defined in OAlg.Entity.Slice.Definition Methods show2 :: SliceFactorDrop s a b -> String Source # | |
| Show2 (HomEmpty s) Source # | |
| Show2 (HomId s) Source # | |
| Show2 (Struct2 m) Source # | |
| (Show2 f, Show2 g) => Show2 (Either2 f g) Source # | |
| Show2 (HomCo m s o) Source # | |
| Show2 (MorCo m s o) Source # | |
| Show2 (PathCo m s o) Source # | |
| Show2 (SliceAdjunction i c d) Source # | |
Defined in OAlg.Entity.Slice.Adjunction Methods show2 :: SliceAdjunction i c d a b -> String Source # | |
| Show2 h => Show2 (HomDisj s o h) Source # | |
| Show2 h => Show2 (SHom r s o h) Source # | |
| Show2 h => Show2 (SMorphism r s o h) Source # | |
| Show2 h => Show2 (Variant2 v h) Source # | |
String is an alias for a list of characters.
String constants in Haskell are values of type String.
That means if you write a string literal like "hello world",
it will have the type [Char], which is the same as String.
Note: You can ask the compiler to automatically infer different types
with the -XOverloadedStrings language extension, for example
"hello world" :: Text. See IsString for more information.
Because String is just a list of characters, you can use normal list functions
to do basic string manipulation. See Data.List for operations on lists.
Performance considerations
[Char] is a relatively memory-inefficient type.
It is a linked list of boxed word-size characters, internally it looks something like:
╭─────┬───┬──╮ ╭─────┬───┬──╮ ╭─────┬───┬──╮ ╭────╮
│ (:) │ │ ─┼─>│ (:) │ │ ─┼─>│ (:) │ │ ─┼─>│ [] │
╰─────┴─┼─┴──╯ ╰─────┴─┼─┴──╯ ╰─────┴─┼─┴──╯ ╰────╯
v v v
'a' 'b' 'c'The String "abc" will use 5*3+1 = 16 (in general 5n+1)
words of space in memory.
Furthermore, operations like (++) (string concatenation) are O(n)
(in the left argument).
For historical reasons, the base library uses String in a lot of places
for the conceptual simplicity, but library code dealing with user-data
should use the text
package for Unicode text, or the the
bytestring package
for binary data.
The character type Char represents Unicode codespace
and its elements are code points as in definitions
D9 and D10 of the Unicode Standard.
Character literals in Haskell are single-quoted: 'Q', 'Я' or 'Ω'.
To represent a single quote itself use '\'', and to represent a backslash
use '\\'. The full grammar can be found in the section 2.6 of the
Haskell 2010 Language Report.
To specify a character by its code point one can use decimal, hexadecimal
or octal notation: '\65', '\x41' and '\o101' are all alternative forms
of 'A'. The largest code point is '\x10ffff'.
There is a special escape syntax for ASCII control characters:
| Escape | Alternatives | Meaning |
|---|---|---|
'\NUL' | '\0' | null character |
'\SOH' | '\1' | start of heading |
'\STX' | '\2' | start of text |
'\ETX' | '\3' | end of text |
'\EOT' | '\4' | end of transmission |
'\ENQ' | '\5' | enquiry |
'\ACK' | '\6' | acknowledge |
'\BEL' | '\7', '\a' | bell (alert) |
'\BS' | '\8', '\b' | backspace |
'\HT' | '\9', '\t' | horizontal tab |
'\LF' | '\10', '\n' | line feed (new line) |
'\VT' | '\11', '\v' | vertical tab |
'\FF' | '\12', '\f' | form feed |
'\CR' | '\13', '\r' | carriage return |
'\SO' | '\14' | shift out |
'\SI' | '\15' | shift in |
'\DLE' | '\16' | data link escape |
'\DC1' | '\17' | device control 1 |
'\DC2' | '\18' | device control 2 |
'\DC3' | '\19' | device control 3 |
'\DC4' | '\20' | device control 4 |
'\NAK' | '\21' | negative acknowledge |
'\SYN' | '\22' | synchronous idle |
'\ETB' | '\23' | end of transmission block |
'\CAN' | '\24' | cancel |
'\EM' | '\25' | end of medium |
'\SUB' | '\26' | substitute |
'\ESC' | '\27' | escape |
'\FS' | '\28' | file separator |
'\GS' | '\29' | group separator |
'\RS' | '\30' | record separator |
'\US' | '\31' | unit separator |
'\SP' | '\32', ' ' | space |
'\DEL' | '\127' | delete |
Instances
| Data Char | Since: base-4.0.0.0 | ||||
Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Char -> c Char # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Char # dataTypeOf :: Char -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Char) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Char) # gmapT :: (forall b. Data b => b -> b) -> Char -> Char # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Char -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Char -> r # gmapQ :: (forall d. Data d => d -> u) -> Char -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Char -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Char -> m Char # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Char -> m Char # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Char -> m Char # | |||||
| Storable Char | Since: base-2.1 | ||||
Defined in Foreign.Storable | |||||
| Bounded Char | Since: base-2.1 | ||||
| Enum Char | Since: base-2.1 | ||||
| Ix Char | Since: base-2.1 | ||||
| Read Char | Since: base-2.1 | ||||
| Show Char | Since: base-2.1 | ||||
| IsChar Char | Since: base-2.1 | ||||
| PrintfArg Char | Since: base-2.1 | ||||
Defined in Text.Printf | |||||
| NFData Char | |||||
Defined in Control.DeepSeq | |||||
| Eq Char | |||||
| Ord Char | |||||
| Verbose Char Source # | |||||
| Validable Char Source # | |||||
| Random Char | |||||
| Uniform Char | |||||
Defined in System.Random.Internal Methods uniformM :: StatefulGen g m => g -> m Char # | |||||
| UniformRange Char | |||||
| IArray UArray Char | |||||
Defined in Data.Array.Base Methods bounds :: Ix i => UArray i Char -> (i, i) # numElements :: Ix i => UArray i Char -> Int # unsafeArray :: Ix i => (i, i) -> [(Int, Char)] -> UArray i Char # unsafeAt :: Ix i => UArray i Char -> Int -> Char # unsafeReplace :: Ix i => UArray i Char -> [(Int, Char)] -> UArray i Char # unsafeAccum :: Ix i => (Char -> e' -> Char) -> UArray i Char -> [(Int, e')] -> UArray i Char # unsafeAccumArray :: Ix i => (Char -> e' -> Char) -> Char -> (i, i) -> [(Int, e')] -> UArray i Char # | |||||
| TestCoercion SChar | Since: base-4.18.0.0 | ||||
Defined in GHC.TypeLits | |||||
| TestEquality SChar | Since: base-4.18.0.0 | ||||
Defined in GHC.TypeLits | |||||
| Lift Char | |||||
| MArray IOUArray Char IO | |||||
Defined in Data.Array.IO.Internals Methods getBounds :: Ix i => IOUArray i Char -> IO (i, i) # getNumElements :: Ix i => IOUArray i Char -> IO Int # newArray :: Ix i => (i, i) -> Char -> IO (IOUArray i Char) # newArray_ :: Ix i => (i, i) -> IO (IOUArray i Char) # unsafeNewArray_ :: Ix i => (i, i) -> IO (IOUArray i Char) # unsafeRead :: Ix i => IOUArray i Char -> Int -> IO Char # unsafeWrite :: Ix i => IOUArray i Char -> Int -> Char -> IO () # | |||||
| Generic1 (URec Char :: k -> Type) | |||||
Defined in GHC.Generics Associated Types
| |||||
| Foldable (UChar :: Type -> Type) | Since: base-4.9.0.0 | ||||
Defined in Data.Foldable Methods fold :: Monoid m => UChar m -> m # foldMap :: Monoid m => (a -> m) -> UChar a -> m # foldMap' :: Monoid m => (a -> m) -> UChar a -> m # foldr :: (a -> b -> b) -> b -> UChar a -> b # foldr' :: (a -> b -> b) -> b -> UChar a -> b # foldl :: (b -> a -> b) -> b -> UChar a -> b # foldl' :: (b -> a -> b) -> b -> UChar a -> b # foldr1 :: (a -> a -> a) -> UChar a -> a # foldl1 :: (a -> a -> a) -> UChar a -> a # elem :: Eq a => a -> UChar a -> Bool # maximum :: Ord a => UChar a -> a # minimum :: Ord a => UChar a -> a # | |||||
| Traversable (UChar :: Type -> Type) | Since: base-4.9.0.0 | ||||
| MArray (STUArray s) Char (ST s) | |||||
Defined in Data.Array.Base Methods getBounds :: Ix i => STUArray s i Char -> ST s (i, i) # getNumElements :: Ix i => STUArray s i Char -> ST s Int # newArray :: Ix i => (i, i) -> Char -> ST s (STUArray s i Char) # newArray_ :: Ix i => (i, i) -> ST s (STUArray s i Char) # unsafeNewArray_ :: Ix i => (i, i) -> ST s (STUArray s i Char) # unsafeRead :: Ix i => STUArray s i Char -> Int -> ST s Char # unsafeWrite :: Ix i => STUArray s i Char -> Int -> Char -> ST s () # | |||||
| Functor (URec Char :: Type -> Type) | Since: base-4.9.0.0 | ||||
| Generic (URec Char p) | |||||
Defined in GHC.Generics Associated Types
| |||||
| Show (URec Char p) | Since: base-4.9.0.0 | ||||
| Eq (URec Char p) | Since: base-4.9.0.0 | ||||
| Ord (URec Char p) | Since: base-4.9.0.0 | ||||
Defined in GHC.Generics | |||||
| data URec Char (p :: k) | Used for marking occurrences of Since: base-4.9.0.0 | ||||
| type Compare (a :: Char) (b :: Char) | |||||
Defined in Data.Type.Ord | |||||
| type Rep1 (URec Char :: k -> Type) | Since: base-4.9.0.0 | ||||
Defined in GHC.Generics | |||||
| type Rep (URec Char p) | Since: base-4.9.0.0 | ||||
Defined in GHC.Generics | |||||
Read
Parsing of Strings, producing values.
Derived instances of Read make the following assumptions, which
derived instances of Show obey:
- If the constructor is defined to be an infix operator, then the
derived
Readinstance will parse only infix applications of the constructor (not the prefix form). - Associativity is not used to reduce the occurrence of parentheses, although precedence may be.
- If the constructor is defined using record syntax, the derived
Readwill parse only the record-syntax form, and furthermore, the fields must be given in the same order as the original declaration. - The derived
Readinstance allows arbitrary Haskell whitespace between tokens of the input string. Extra parentheses are also allowed.
For example, given the declarations
infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of Read in Haskell 2010 is equivalent to
instance (Read a) => Read (Tree a) where
readsPrec d r = readParen (d > app_prec)
(\r -> [(Leaf m,t) |
("Leaf",s) <- lex r,
(m,t) <- readsPrec (app_prec+1) s]) r
++ readParen (d > up_prec)
(\r -> [(u:^:v,w) |
(u,s) <- readsPrec (up_prec+1) r,
(":^:",t) <- lex s,
(v,w) <- readsPrec (up_prec+1) t]) r
where app_prec = 10
up_prec = 5Note that right-associativity of :^: is unused.
The derived instance in GHC is equivalent to
instance (Read a) => Read (Tree a) where
readPrec = parens $ (prec app_prec $ do
Ident "Leaf" <- lexP
m <- step readPrec
return (Leaf m))
+++ (prec up_prec $ do
u <- step readPrec
Symbol ":^:" <- lexP
v <- step readPrec
return (u :^: v))
where app_prec = 10
up_prec = 5
readListPrec = readListPrecDefaultWhy do both readsPrec and readPrec exist, and why does GHC opt to
implement readPrec in derived Read instances instead of readsPrec?
The reason is that readsPrec is based on the ReadS type, and although
ReadS is mentioned in the Haskell 2010 Report, it is not a very efficient
parser data structure.
readPrec, on the other hand, is based on a much more efficient ReadPrec
datatype (a.k.a "new-style parsers"), but its definition relies on the use
of the RankNTypes language extension. Therefore, readPrec (and its
cousin, readListPrec) are marked as GHC-only. Nevertheless, it is
recommended to use readPrec instead of readsPrec whenever possible
for the efficiency improvements it brings.
As mentioned above, derived Read instances in GHC will implement
readPrec instead of readsPrec. The default implementations of
readsPrec (and its cousin, readList) will simply use readPrec under
the hood. If you are writing a Read instance by hand, it is recommended
to write it like so:
instanceReadT wherereadPrec= ...readListPrec=readListPrecDefault
Instances
| Read Version | Since: base-2.1 |
| Read CBool | |
| Read CChar | |
| Read CClock | |
| Read CDouble | |
| Read CFloat | |
| Read CInt | |
| Read CIntMax | |
| Read CIntPtr | |
| Read CLLong | |
| Read CLong | |
| Read CPtrdiff | |
| Read CSChar | |
| Read CSUSeconds | |
Defined in Foreign.C.Types Methods readsPrec :: Int -> ReadS CSUSeconds # readList :: ReadS [CSUSeconds] # readPrec :: ReadPrec CSUSeconds # readListPrec :: ReadPrec [CSUSeconds] # | |
| Read CShort | |
| Read CSigAtomic | |
Defined in Foreign.C.Types Methods readsPrec :: Int -> ReadS CSigAtomic # readList :: ReadS [CSigAtomic] # readPrec :: ReadPrec CSigAtomic # readListPrec :: ReadPrec [CSigAtomic] # | |
| Read CSize | |
| Read CTime | |
| Read CUChar | |
| Read CUInt | |
| Read CUIntMax | |
| Read CUIntPtr | |
| Read CULLong | |
| Read CULong | |
| Read CUSeconds | |
| Read CUShort | |
| Read CWchar | |
| Read IntPtr | |
| Read WordPtr | |
| Read Void | Reading a Since: base-4.8.0.0 |
| Read ByteOrder | Since: base-4.11.0.0 |
| Read Associativity | Since: base-4.6.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS Associativity # readList :: ReadS [Associativity] # | |
| Read DecidedStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS DecidedStrictness # readList :: ReadS [DecidedStrictness] # | |
| Read Fixity | Since: base-4.6.0.0 |
| Read SourceStrictness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS SourceStrictness # readList :: ReadS [SourceStrictness] # | |
| Read SourceUnpackedness | Since: base-4.9.0.0 |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS SourceUnpackedness # readList :: ReadS [SourceUnpackedness] # | |
| Read SeekMode | Since: base-4.2.0.0 |
| Read ExitCode | |
| Read BufferMode | Since: base-4.2.0.0 |
Defined in GHC.IO.Handle.Types Methods readsPrec :: Int -> ReadS BufferMode # readList :: ReadS [BufferMode] # readPrec :: ReadPrec BufferMode # readListPrec :: ReadPrec [BufferMode] # | |
| Read Newline | Since: base-4.3.0.0 |
| Read NewlineMode | Since: base-4.3.0.0 |
Defined in GHC.IO.Handle.Types Methods readsPrec :: Int -> ReadS NewlineMode # readList :: ReadS [NewlineMode] # readPrec :: ReadPrec NewlineMode # readListPrec :: ReadPrec [NewlineMode] # | |
| Read IOMode | Since: base-4.2.0.0 |
| Read Int16 | Since: base-2.1 |
| Read Int32 | Since: base-2.1 |
| Read Int64 | Since: base-2.1 |
| Read Int8 | Since: base-2.1 |
| Read GCDetails | Since: base-4.10.0.0 |
| Read RTSStats | Since: base-4.10.0.0 |
| Read SomeChar | |
| Read SomeSymbol | Since: base-4.7.0.0 |
Defined in GHC.TypeLits Methods readsPrec :: Int -> ReadS SomeSymbol # readList :: ReadS [SomeSymbol] # readPrec :: ReadPrec SomeSymbol # readListPrec :: ReadPrec [SomeSymbol] # | |
| Read SomeNat | Since: base-4.7.0.0 |
| Read GeneralCategory | Since: base-2.1 |
Defined in GHC.Read Methods readsPrec :: Int -> ReadS GeneralCategory # readList :: ReadS [GeneralCategory] # | |
| Read Word16 | Since: base-2.1 |
| Read Word32 | Since: base-2.1 |
| Read Word64 | Since: base-2.1 |
| Read Word8 | Since: base-2.1 |
| Read CBlkCnt | |
| Read CBlkSize | |
| Read CCc | |
| Read CClockId | |
| Read CDev | |
| Read CFsBlkCnt | |
| Read CFsFilCnt | |
| Read CGid | |
| Read CId | |
| Read CIno | |
| Read CKey | |
| Read CMode | |
| Read CNfds | |
| Read CNlink | |
| Read COff | |
| Read CPid | |
| Read CRLim | |
| Read CSocklen | |
| Read CSpeed | |
| Read CSsize | |
| Read CTcflag | |
| Read CUid | |
| Read Fd | |
| Read Lexeme | Since: base-2.1 |
| Read ByteString | |
Defined in Data.ByteString.Internal.Type Methods readsPrec :: Int -> ReadS ByteString # readList :: ReadS [ByteString] # readPrec :: ReadPrec ByteString # readListPrec :: ReadPrec [ByteString] # | |
| Read ByteString | |
Defined in Data.ByteString.Lazy.Internal Methods readsPrec :: Int -> ReadS ByteString # readList :: ReadS [ByteString] # readPrec :: ReadPrec ByteString # readListPrec :: ReadPrec [ByteString] # | |
| Read ShortByteString | |
Defined in Data.ByteString.Short.Internal Methods readsPrec :: Int -> ReadS ShortByteString # readList :: ReadS [ShortByteString] # | |
| Read Ordering | Since: base-2.1 |
| Read Stochastic Source # | |
Defined in OAlg.Control.Validate Methods readsPrec :: Int -> ReadS Stochastic # readList :: ReadS [Stochastic] # readPrec :: ReadPrec Stochastic # readListPrec :: ReadPrec [Stochastic] # | |
| Read RdcState Source # | |
| Read Symbol Source # | |
| Read Variant Source # | |
| Read Month | Read as |
| Read Quarter | Read as |
| Read QuarterOfYear | |
Defined in Data.Time.Calendar.Quarter Methods readsPrec :: Int -> ReadS QuarterOfYear # readList :: ReadS [QuarterOfYear] # | |
| Read DiffTime | |
| Read Integer | Since: base-2.1 |
| Read Natural | Since: base-4.8.0.0 |
| Read () | Since: base-2.1 |
| Read Bool | Since: base-2.1 |
| Read Char | Since: base-2.1 |
| Read Double | Since: base-2.1 |
| Read Float | Since: base-2.1 |
| Read Int | Since: base-2.1 |
| Read Word | Since: base-4.5.0.0 |
| Read a => Read (ZipList a) | Since: base-4.7.0.0 |
| Read a => Read (And a) | Since: base-4.16 |
| Read a => Read (Iff a) | Since: base-4.16 |
| Read a => Read (Ior a) | Since: base-4.16 |
| Read a => Read (Xor a) | Since: base-4.16 |
| Read a => Read (Complex a) | Since: base-2.1 |
| Read a => Read (Identity a) | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
| Read a => Read (First a) | Since: base-2.1 |
| Read a => Read (Last a) | Since: base-2.1 |
| Read a => Read (Down a) | This instance would be equivalent to the derived instances of the
Since: base-4.7.0.0 |
| Read a => Read (First a) | Since: base-4.9.0.0 |
| Read a => Read (Last a) | Since: base-4.9.0.0 |
| Read a => Read (Max a) | Since: base-4.9.0.0 |
| Read a => Read (Min a) | Since: base-4.9.0.0 |
| Read m => Read (WrappedMonoid m) | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods readsPrec :: Int -> ReadS (WrappedMonoid m) # readList :: ReadS [WrappedMonoid m] # readPrec :: ReadPrec (WrappedMonoid m) # readListPrec :: ReadPrec [WrappedMonoid m] # | |
| Read a => Read (NonEmpty a) | Since: base-4.11.0.0 |
| Read p => Read (Par1 p) | Since: base-4.7.0.0 |
| (Integral a, Read a) => Read (Ratio a) | Since: base-2.1 |
| Read x => Read (Id x) Source # | |
| Read x => Read (Closure x) Source # | |
| Read x => Read (Op x) Source # | |
| Read a => Read (Maybe a) | Since: base-2.1 |
| Read a => Read (Solo a) | Since: base-4.15 |
| Read a => Read [a] | Since: base-2.1 |
| (Ix ix, Read ix, Read e, IArray UArray e) => Read (UArray ix e) | |
| (Read a, Read b) => Read (Either a b) | Since: base-3.0 |
| HasResolution a => Read (Fixed a) | Since: base-4.3.0.0 |
| Read (Proxy t) | Since: base-4.7.0.0 |
| (Read a, Read b) => Read (Arg a b) | Since: base-4.9.0.0 |
| (Ix a, Read a, Read b) => Read (Array a b) | Since: base-2.1 |
| Read (U1 p) | Since: base-4.9.0.0 |
| Read (V1 p) | Since: base-4.9.0.0 |
| (Read1 m, Read a) => Read (MaybeT m a) | |
| (Read a, Read b) => Read (a, b) | Since: base-2.1 |
| Read a => Read (Const a b) | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
| Read (f a) => Read (Ap f a) | Since: base-4.12.0.0 |
| Coercible a b => Read (Coercion a b) | Since: base-4.7.0.0 |
| a ~ b => Read (a :~: b) | Since: base-4.7.0.0 |
| Read (f p) => Read (Rec1 f p) | Since: base-4.7.0.0 |
| (Read e, Read1 m, Read a) => Read (ExceptT e m a) | |
| (Read1 f, Read a) => Read (IdentityT f a) | |
| (Read w, Read1 m, Read a) => Read (WriterT w m a) | |
| (Read w, Read1 m, Read a) => Read (WriterT w m a) | |
| (Read a, Read b, Read c) => Read (a, b, c) | Since: base-2.1 |
| (Read (f a), Read (g a)) => Read (Product f g a) | Since: base-4.18.0.0 |
| (Read (f a), Read (g a)) => Read (Sum f g a) | Since: base-4.18.0.0 |
| a ~~ b => Read (a :~~: b) | Since: base-4.10.0.0 |
| (Read (f p), Read (g p)) => Read ((f :*: g) p) | Since: base-4.7.0.0 |
| (Read (f p), Read (g p)) => Read ((f :+: g) p) | Since: base-4.7.0.0 |
| Read c => Read (K1 i c p) | Since: base-4.7.0.0 |
| Read (Proxy2 a b) Source # | |
| (Read a, Read b, Read c, Read d) => Read (a, b, c, d) | Since: base-2.1 |
| Read (f (g a)) => Read (Compose f g a) | Since: base-4.18.0.0 |
| Read (f (g p)) => Read ((f :.: g) p) | Since: base-4.7.0.0 |
| Read (f p) => Read (M1 i c f p) | Since: base-4.7.0.0 |
| (Read a, Read b, Read c, Read d, Read e) => Read (a, b, c, d, e) | Since: base-2.1 |
| Read (Proxy3 a b c) Source # | |
| (Read a, Read b, Read c, Read d, Read e, Read f) => Read (a, b, c, d, e, f) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g) => Read (a, b, c, d, e, f, g) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h) => Read (a, b, c, d, e, f, g, h) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i) => Read (a, b, c, d, e, f, g, h, i) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j) => Read (a, b, c, d, e, f, g, h, i, j) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k) => Read (a, b, c, d, e, f, g, h, i, j, k) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l) => Read (a, b, c, d, e, f, g, h, i, j, k, l) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m, Read n) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m, Read n, Read o) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | Since: base-2.1 |
Defined in GHC.Read | |
read :: Read a => String -> a #
The read function reads input from a string, which must be
completely consumed by the input process. read fails with an error if the
parse is unsuccessful, and it is therefore discouraged from being used in
real applications. Use readMaybe or readEither for safe alternatives.
>>>read "123" :: Int123
>>>read "hello" :: Int*** Exception: Prelude.read: no parse