- data ReadP t a
- get :: ReadP t t
- look :: ReadP t [t]
- (+++) :: ReadP t a -> ReadP t a -> ReadP t a
- (<++) :: ReadP t a -> ReadP t a -> ReadP t a
- gather :: ReadP t a -> ReadP t ([t], a)
- parse :: ReadP t a -> [t] -> [a]
- parse' :: ReadP t a -> [t] -> Either a [t]
- pfail :: ReadP t a
- satisfy :: (t -> Bool) -> ReadP t t
- char :: Eq t => t -> ReadP t t
- string :: Eq t => [t] -> ReadP t [t]
- munch :: (t -> Bool) -> ReadP t [t]
- munch1 :: (t -> Bool) -> ReadP t [t]
- skipSpaces :: ReadP Char ()
- choice :: [ReadP t a] -> ReadP t a
- count :: Int -> ReadP t a -> ReadP t [a]
- between :: ReadP t open -> ReadP t close -> ReadP t a -> ReadP t a
- option :: a -> ReadP t a -> ReadP t a
- optional :: ReadP t a -> ReadP t ()
- many :: ReadP t a -> ReadP t [a]
- many1 :: ReadP t a -> ReadP t [a]
- skipMany :: ReadP t a -> ReadP t ()
- skipMany1 :: ReadP t a -> ReadP t ()
- sepBy :: ReadP t a -> ReadP t sep -> ReadP t [a]
- sepBy1 :: ReadP t a -> ReadP t sep -> ReadP t [a]
- endBy :: ReadP t a -> ReadP t sep -> ReadP t [a]
- endBy1 :: ReadP t a -> ReadP t sep -> ReadP t [a]
- chainr :: ReadP t a -> ReadP t (a -> a -> a) -> a -> ReadP t a
- chainl :: ReadP t a -> ReadP t (a -> a -> a) -> a -> ReadP t a
- chainl1 :: ReadP t a -> ReadP t (a -> a -> a) -> ReadP t a
- chainr1 :: ReadP t a -> ReadP t (a -> a -> a) -> ReadP t a
- manyTill :: ReadP t a -> ReadP t end -> ReadP t [a]
The ReadP
type
Primitive operations
Look-ahead: returns the part of the input that is left, without consuming it.
(<++) :: ReadP t a -> ReadP t a -> ReadP t aSource
Local, exclusive, left-biased choice: If left parser locally produces any result at all, then right parser is not used.
gather :: ReadP t a -> ReadP t ([t], a)Source
Transforms a parser into one that does the same, but
in addition returns the exact characters read.
IMPORTANT NOTE: gather
gives a runtime error if its first argument
is built using any occurrences of readS_to_P.
Parse
parse :: ReadP t a -> [t] -> [a]Source
Run a parser on a list of tokens. Returns the list of complete matches.
Other operations
satisfy :: (t -> Bool) -> ReadP t tSource
Consumes and returns the next character, if it satisfies the specified predicate.
munch :: (t -> Bool) -> ReadP t [t]Source
Parses the first zero or more characters satisfying the predicate.
munch1 :: (t -> Bool) -> ReadP t [t]Source
Parses the first one or more characters satisfying the predicate.
skipSpaces :: ReadP Char ()Source
Skips all whitespace.
count :: Int -> ReadP t a -> ReadP t [a]Source
count n p
parses n
occurrences of p
in sequence. A list of
results is returned.
between :: ReadP t open -> ReadP t close -> ReadP t a -> ReadP t aSource
between open close p
parses open
, followed by p
and finally
close
. Only the value of p
is returned.
option :: a -> ReadP t a -> ReadP t aSource
option x p
will either parse p
or return x
without consuming
any input.
sepBy :: ReadP t a -> ReadP t sep -> ReadP t [a]Source
sepBy p sep
parses zero or more occurrences of p
, separated by sep
.
Returns a list of values returned by p
.
sepBy1 :: ReadP t a -> ReadP t sep -> ReadP t [a]Source
sepBy1 p sep
parses one or more occurrences of p
, separated by sep
.
Returns a list of values returned by p
.
endBy :: ReadP t a -> ReadP t sep -> ReadP t [a]Source
endBy p sep
parses zero or more occurrences of p
, separated and ended
by sep
.
endBy1 :: ReadP t a -> ReadP t sep -> ReadP t [a]Source
endBy p sep
parses one or more occurrences of p
, separated and ended
by sep
.
chainr :: ReadP t a -> ReadP t (a -> a -> a) -> a -> ReadP t aSource
chainr p op x
parses zero or more occurrences of p
, separated by op
.
Returns a value produced by a right associative application of all
functions returned by op
. If there are no occurrences of p
, x
is
returned.
chainl :: ReadP t a -> ReadP t (a -> a -> a) -> a -> ReadP t aSource
chainl p op x
parses zero or more occurrences of p
, separated by op
.
Returns a value produced by a left associative application of all
functions returned by op
. If there are no occurrences of p
, x
is
returned.
chainl1 :: ReadP t a -> ReadP t (a -> a -> a) -> ReadP t aSource
Like chainl
, but parses one or more occurrences of p
.
chainr1 :: ReadP t a -> ReadP t (a -> a -> a) -> ReadP t aSource
Like chainr
, but parses one or more occurrences of p
.
manyTill :: ReadP t a -> ReadP t end -> ReadP t [a]Source
manyTill p end
parses zero or more occurrences of p
, until end
succeeds. Returns a list of values returned by p
.
Properties
The following are QuickCheck specifications of what the combinators do. These can be seen as formal specifications of the behavior of the combinators.
We use bags to give semantics to the combinators.
type Bag a = [a]
Equality on bags does not care about the order of elements.
(=~) :: Ord a => Bag a -> Bag a -> Bool xs =~ ys = sort xs == sort ys
A special equality operator to avoid unresolved overloading when testing the properties.
(=~.) :: Bag (Int,String) -> Bag (Int,String) -> Bool (=~.) = (=~)
Here follow the properties:
prop_Get_Nil = readP_to_S get [] =~ [] prop_Get_Cons c s = readP_to_S get (c:s) =~ [(c,s)] prop_Look s = readP_to_S look s =~ [(s,s)] prop_Fail s = readP_to_S pfail s =~. [] prop_Return x s = readP_to_S (return x) s =~. [(x,s)] prop_Bind p k s = readP_to_S (p >>= k) s =~. [ ys'' | (x,s') <- readP_to_S p s , ys'' <- readP_to_S (k (x::Int)) s' ] prop_Plus p q s = readP_to_S (p +++ q) s =~. (readP_to_S p s ++ readP_to_S q s) prop_LeftPlus p q s = readP_to_S (p <++ q) s =~. (readP_to_S p s +<+ readP_to_S q s) where [] +<+ ys = ys xs +<+ _ = xs prop_Gather s = forAll readPWithoutReadS $ \p -> readP_to_S (gather p) s =~ [ ((pre,x::Int),s') | (x,s') <- readP_to_S p s , let pre = take (length s - length s') s ] prop_String_Yes this s = readP_to_S (string this) (this ++ s) =~ [(this,s)] prop_String_Maybe this s = readP_to_S (string this) s =~ [(this, drop (length this) s) | this `isPrefixOf` s] prop_Munch p s = readP_to_S (munch p) s =~ [(takeWhile p s, dropWhile p s)] prop_Munch1 p s = readP_to_S (munch1 p) s =~ [(res,s') | let (res,s') = (takeWhile p s, dropWhile p s), not (null res)] prop_Choice ps s = readP_to_S (choice ps) s =~. readP_to_S (foldr (+++) pfail ps) s prop_ReadS r s = readP_to_S (readS_to_P r) s =~. r s