Text.XML.HaXml.Lex

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Text.XML.HaXml.Lex
Contents
Entry points to the lexer Token and position types
Description
You don't normally need to use this Lex module directly - it is called automatically by the parser. (This interface is only exposed for debugging purposes.) This is a hand-written lexer for tokenising the text of an XML document so that it is ready for parsing. It attaches position information in (line,column) format to every token. The main entry point is `xmlLex`. A secondary entry point, `xmlReLex`, is provided for when the parser needs to stuff a string back onto the front of the text and re-tokenise it (typically when expanding macros). As one would expect, the lexer is essentially a small finite state machine.
Synopsis
xmlLex :: String -> String -> [Token]
xmlReLex :: Posn -> String -> [Token]
posInNewCxt :: String -> Maybe Posn -> Posn
type Token = Either String (Posn, TokenT)
data Posn = Pn String !Int !Int (Maybe Posn)
data TokenT
= TokCommentOpen
| TokCommentClose
| TokPIOpen
| TokPIClose
| TokSectionOpen
| TokSectionClose
| TokSection Section
| TokSpecialOpen
| TokSpecial Special
| TokEndOpen
| TokEndClose
| TokAnyOpen
| TokAnyClose
| TokSqOpen
| TokSqClose
| TokEqual
| TokQuery
| TokStar
| TokPlus
| TokAmp
| TokSemi
| TokHash
| TokBraOpen
| TokBraClose
| TokPipe
| TokPercent
| TokComma
| TokQuote
| TokName String
| TokFreeText String
| TokNull
data Special
= DOCTYPEx
| ELEMENTx
| ATTLISTx
| ENTITYx
| NOTATIONx
data Section
= CDATAx
| INCLUDEx
| IGNOREx
Entry points to the lexer
xmlLex :: String -> String -> [Token]
The first argument to `xmlLex` is the filename (used for source positions, especially in error messages), and the second is the string content of the XML file.
xmlReLex :: Posn -> String -> [Token]
`xmlReLex` is used when the parser expands a macro (PE reference). The expansion of the macro must be re-lexed as if for the first time.
posInNewCxt :: String -> Maybe Posn -> Posn
`posInNewCxt name pos` creates a new source position from an old one. It is used when opening a new file (e.g. a DTD inclusion), to denote the start of the file `name`, but retain the stacked information that it was included from the old `pos`.
Token and position types
type Token = Either String (Posn, TokenT)
All tokens are paired up with a source position. Lexical errors are passed back through the `Either` type.
data Posn
Source positions contain a filename, line, column, and an inclusion point, which is itself another source position, recursively.
Constructors
Pn String !Int !Int (Maybe Posn) |
Instances
Show Posn
data TokenT
The basic token type.
Constructors
TokCommentOpen | <!--
TokCommentClose | -->
TokPIOpen | <?
TokPIClose | ?>
TokSectionOpen | <![
TokSectionClose | ]]>
TokSection Section | CDATA INCLUDE IGNORE etc
TokSpecialOpen | <!
TokSpecial Special | DOCTYPE ELEMENT ATTLIST etc
TokEndOpen | </
TokEndClose | />
TokAnyOpen | <
TokAnyClose | >
TokSqOpen | [
TokSqClose | ]
TokEqual | =
TokQuery | ?
TokStar | *
TokPlus | +
TokAmp | &
TokSemi | ;
TokHash | #
TokBraOpen | (
TokBraClose | )
TokPipe | |
TokPercent | %
TokComma | ,
TokQuote | '' or ""
TokName String | begins with letter
TokFreeText String | any character data
TokNull | fake token
Instances
Show TokenT
data Special
Constructors
DOCTYPEx |
ELEMENTx |
ATTLISTx |
ENTITYx |
NOTATIONx |
data Section
Constructors
CDATAx |
INCLUDEx |
IGNOREx |
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