/usr/lib/hugs/packages/HaXml/Text/XML/HaXml/Xtract/Parse.hs is in libhugs-haxml-bundled 98.200609.21-5.3.
This file is owned by root:root, with mode 0o644.
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-- tokenised internally by the lexer 'lexXtract'.)
-- See <http://www.haskell.org/HaXml/Xtract.html> for the grammar that
-- is accepted.
-- Because the original Xtract grammar was left-recursive, we have
-- transformed it into a non-left-recursive form.
module Text.XML.HaXml.Xtract.Parse (parseXtract,xtract) where
import Text.ParserCombinators.Poly hiding (bracket)
import Text.XML.HaXml.Xtract.Lex
import Text.XML.HaXml.Xtract.Combinators
import Text.XML.HaXml.Combinators
import List(isPrefixOf)
-- | To convert an Xtract query into an ordinary HaXml combinator expression.
xtract :: String -> CFilter i
xtract query = dfilter (parseXtract query)
-- | The cool thing is that the Xtract command parser directly builds
-- a higher-order 'DFilter' (see "Text.XML.HaXml.Xtract.Combinators")
-- which can be applied to an XML document without further ado.
-- (@parseXtract@ halts the program if a parse error is found.)
parseXtract :: String -> DFilter i
parseXtract = either error id . parseXtract'
-- | @parseXtract'@ returns error messages through the Either type.
parseXtract' :: String -> Either String (DFilter i)
parseXtract' = fst . runParser xql . lexXtract
xql = aquery (local keep)
---- Auxiliary Parsing Functions ----
type XParser a = Parser (Either String (Posn,TokenT)) a
string :: XParser String
string = P (\inp -> case inp of
(Left err: _) -> (Left (False,err), inp)
(Right (p,TokString n):ts) -> (Right n, ts)
ts -> (Left (False,"expected a string"), ts) )
number :: XParser Integer
number = P (\inp -> case inp of
(Left err: _) -> (Left (False,err), inp)
(Right (p,TokNum n):ts) -> (Right n, ts)
ts -> (Left (False,"expected a number"), ts) )
symbol :: String -> XParser ()
symbol s = P (\inp -> case inp of
(Left err: _) -> (Left (False,err), inp)
(Right (p, Symbol n):ts) | n==s -> (Right (), ts)
ts -> (Left (False,"expected symbol "++s), ts) )
quote = oneOf [ symbol "'", symbol "\"" ]
pam fs x = [ f x | f <- fs ]
{--- original Xtract grammar ----
query = string tagname
| string * tagname prefix
| * string tagname suffix
| * any element
| - chardata
| ( query )
| query / query parent/child relationship
| query // query deep inside
| query + query union of queries
| query [predicate]
| query [positions]
predicate = quattr has attribute
| quattr op ' string ' attribute has value
| quattr op " string " attribute has value
| quattr op quattr attribute value comparison (lexical)
| quattr nop integer attribute has value (numerical)
| quattr nop quattr attribute value comparison (numerical)
| ( predicate ) bracketting
| predicate & predicate logical and
| predicate | predicate logical or
| ~ predicate logical not
attribute = @ string has attribute
| query / @ string child has attribute
| - has textual content
| query / - child has textual content
quattr = query
| attribute
op = = equal to
| != not equal to
| < less than
| <= less than or equal to
| > greater than
| >= greater than or equal to
nop = .=. equal to
| .!=. not equal to
| .<. less than
| .<=. less than or equal to
| .>. greater than
| .>=. greater than or equal to
positions = position {, positions} multiple positions
| position - position ranges
position = integer numbering is from 0 upwards
| $ last
---- transformed grammar (removing left recursion)
aquery = ./ tquery -- current context
| tquery -- also current context
| / tquery -- root context
| // tquery -- deep context from root
tquery = ( tquery ) xquery
| tag xquery
| - -- fixes original grammar ("-/*" is incorrect)
tag = string *
| string
| * string
| *
xquery = / tquery
| // tquery
| / @ string -- new: print attribute value
| + tquery
| [ tpredicate ] xquery
| [ positions ] xquery
| lambda
tpredicate = vpredicate upredicate
upredicate = & tpredicate
| | tpredicate
| lambda
vpredicate = ( tpredicate )
| ~ tpredicate
| tattribute
tattribute = aquery uattribute
| @ string vattribute
uattribute = / @ string vattribute
| vattribute
vattribute = op wattribute
| op ' string '
| nop wattribute
| nop integer
| lambda
wattribute = @ string
| aquery / @ string
| aquery
positions = simplepos commapos
simplepos = integer range
| $
range = - integer
| - $
| lambda
commapos = , simplepos commapos
| lambda
op = =
| !=
| <
| <=
| >
| >=
nop = .=.
| .!=.
| .<.
| .<=.
| .>.
| .>=.
-}
bracket :: XParser a -> XParser a
bracket p =
do symbol "("
x <- p
symbol ")"
return x
---- Xtract parsers ----
-- aquery takes a localisation filter, but if the query string starts
-- from the root, we ignore the local context
aquery :: DFilter i -> XParser (DFilter i)
aquery localise = oneOf
[ do symbol "//"
tquery [oglobo deep]
, do symbol "/"
tquery [oglobo id]
, do symbol "./"
tquery [(localise //>>)]
, do tquery [(localise //>>)]
]
tquery :: [DFilter i->DFilter i] -> XParser (DFilter i)
tquery [] = tquery [id]
tquery (qf:cxt) = oneOf
[ do q <- bracket (tquery (qf:qf:cxt))
xquery cxt q
, do q <- xtag
xquery cxt (qf q)
, do symbol "-"
return (qf (local txt))
]
xtag :: XParser (DFilter i)
xtag = oneOf
[ do s <- string
symbol "*"
return (local (tagWith (s `isPrefixOf`)))
, do s <- string
return (local (tag s))
, do symbol "*"
s <- string
return (local (tagWith (((reverse s) `isPrefixOf`) . reverse)))
, do symbol "*"
return (local elm)
]
xquery :: [DFilter i->DFilter i] -> DFilter i -> XParser (DFilter i)
xquery cxt q1 = oneOf
[ do symbol "/"
( do symbol "@"
attr <- string
return (oiffindo attr (\s->local (literal s)) ononeo `ooo` q1)
`onFail`
tquery ((q1 //>>):cxt) )
, do symbol "//"
tquery ((\q2-> (oloco deep) q2 `ooo` local children `ooo` q1):cxt)
, do symbol "+"
q2 <- tquery cxt
return (ocato [q1,q2])
, do symbol "["
is <- iindex -- now extended to multiple indexes
symbol "]"
xquery cxt (\xml-> concat . pam is . q1 xml)
, do symbol "["
p <- tpredicate
symbol "]"
xquery cxt (q1 `owitho` p)
, return q1
]
tpredicate :: XParser (DFilter i)
tpredicate =
do p <- vpredicate
f <- upredicate
return (f p)
upredicate :: XParser (DFilter i->DFilter i)
upredicate = oneOf
[ do symbol "&"
p2 <- tpredicate
return (`ooo` p2)
, do symbol "|"
p2 <- tpredicate
return (||>|| p2)
, return id
]
vpredicate :: XParser (DFilter i)
vpredicate = oneOf
[ do bracket tpredicate
, do symbol "~"
p <- tpredicate
return (local keep `owithouto` p)
, do tattribute
]
tattribute :: XParser (DFilter i)
tattribute = oneOf
[ do q <- aquery (local keep)
uattribute q
, do symbol "@"
s <- string
vattribute (local keep, local (attr s), oiffindo s)
]
uattribute :: DFilter i -> XParser (DFilter i)
uattribute q = oneOf
[ do symbol "/"
symbol "@"
s <- string
vattribute (q, local (attr s), oiffindo s)
, do vattribute (q, local keep, oifTxto)
]
vattribute :: (DFilter i, DFilter i, (String->DFilter i)->DFilter i->DFilter i)
-> XParser (DFilter i)
vattribute (q,a,iffn) = oneOf
[ do cmp <- op
quote
s2 <- string
quote
return ((iffn (\s1->if cmp s1 s2 then okeepo else ononeo) ononeo)
`ooo` q)
, do cmp <- op
(q2,iffn2) <- wattribute
return ((iffn (\s1-> iffn2 (\s2-> if cmp s1 s2 then okeepo else ononeo)
ononeo)
ononeo) `ooo` q)
, do cmp <- nop
n <- number
return ((iffn (\s->if cmp (read s) n then okeepo else ononeo) ononeo)
`ooo` q)
, do cmp <- nop
(q2,iffn2) <- wattribute
return ((iffn (\s1-> iffn2 (\s2-> if cmp (read s1) (read s2) then okeepo
else ononeo)
ononeo)
ononeo) `ooo` q)
, do return ((a `ooo` q))
]
wattribute :: XParser (DFilter i, (String->DFilter i)->DFilter i->DFilter i)
wattribute = oneOf
[ do symbol "@"
s <- string
return (okeepo, oiffindo s)
, do q <- aquery okeepo
symbol "/"
symbol "@"
s <- string
return (q, oiffindo s)
, do q <- aquery okeepo
return (q, oifTxto)
]
iindex :: XParser [[a]->[a]]
iindex =
do i <- simpleindex
is <- idxcomma
return (i:is)
simpleindex :: XParser ([a]->[a])
simpleindex = oneOf
[ do n <- number
r <- rrange n
return r
, do symbol "$"
return (keep . last)
]
rrange, numberdollar :: Integer -> XParser ([a]->[a])
rrange n1 = oneOf
[ do symbol "-"
numberdollar n1
, return (keep.(!!(fromInteger n1)))
]
numberdollar n1 = oneOf
[ do n2 <- number
return (take (fromInteger (1+n2-n1)) . drop (fromInteger n1))
, do symbol "$"
return (drop (fromInteger n1))
]
idxcomma :: XParser [[a]->[a]]
idxcomma = oneOf
[ do symbol ","
r <- simpleindex
rs <- idxcomma
return (r:rs)
, return []
]
op :: XParser (String->String->Bool)
op = oneOf
[ do symbol "="; return (==)
, do symbol "!="; return (/=)
, do symbol "<"; return (<)
, do symbol "<="; return (<=)
, do symbol ">"; return (>)
, do symbol ">="; return (>=)
]
nop :: XParser (Integer->Integer->Bool)
nop = oneOf
[ do symbol ".=."; return (==)
, do symbol ".!=."; return (/=)
, do symbol ".<."; return (<)
, do symbol ".<=."; return (<=)
, do symbol ".>."; return (>)
, do symbol ".>=."; return (>=)
]
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