Text.HTML.TagSoup

This module is for extracting information out of unstructured HTML code, sometimes known as tag-soup. This is for situations where the author of the HTML is not cooperating with the person trying to extract the information, but is also not trying to hide the information.

The standard practice is to parse a String to Tags using parseTags, then operate upon it to extract the necessary information.

Data structures and parsing

data Tag

An HTML element, a document is [Tag]. There is no requirement for TagOpen and TagClose to match

Constructors

TagOpen String [Attribute]

An open tag with Attributes in their original order.

TagClose String

A closing tag

TagText String

A text node, guaranteed not to be the empty string

TagComment String

A comment

TagWarning String

Meta: Mark a syntax error in the input file

TagPosition !Row !Column

Meta: The position of a parsed element

Instances

Eq Tag

Ord Tag

Show Tag

TagRep Tag

type Attribute = (String, String)

An HTML attribute id="name" generates ("id","name")

module Text.HTML.TagSoup.Parser

canonicalizeTags :: [Tag] -> [Tag]

Turns all tag names to lower case and converts DOCTYPE to upper case.

Tag identification

isTagOpen :: Tag -> Bool

Test if a Tag is a TagOpen

isTagClose :: Tag -> Bool

Test if a Tag is a TagClose

isTagText :: Tag -> Bool

Test if a Tag is a TagText

isTagWarning :: Tag -> Bool

Test if a Tag is a TagWarning

isTagOpenName :: String -> Tag -> Bool

Returns True if the Tag is TagOpen and matches the given name

isTagCloseName :: String -> Tag -> Bool

Returns True if the Tag is TagClose and matches the given name

Extraction

fromTagText :: Tag -> String

Extract the string from within TagText, crashes if not a TagText

fromAttrib :: String -> Tag -> String

Extract an attribute, crashes if not a TagOpen. Returns "" if no attribute present.

maybeTagText :: Tag -> Maybe String

Extract the string from within TagText, otherwise Nothing

maybeTagWarning :: Tag -> Maybe String

Extract the string from within TagWarning, otherwise Nothing

innerText :: [Tag] -> String

Extract all text content from tags (similar to Verbatim found in HaXml)

Utility

sections :: (a -> Bool) -> [a] -> [[a]]

This function takes a list, and returns all suffixes whose first item matches the predicate.

partitions :: (a -> Bool) -> [a] -> [[a]]

This function is similar to sections, but splits the list so no element appears in any two partitions.

Combinators

class TagRep a

Define a class to allow String's or Tag's to be used as matches

Instances

TagRep Tag

IsChar c => TagRep [c]

class IsChar a

Instances

IsChar Char

(~==) :: TagRep t => Tag -> t -> Bool

Performs an inexact match, the first item should be the thing to match. If the second item is a blank string, that is considered to match anything. For example:

 (TagText "test" ~== TagText ""    ) == True
 (TagText "test" ~== TagText "test") == True
 (TagText "test" ~== TagText "soup") == False

For TagOpen missing attributes on the right are allowed.

(~/=) :: TagRep t => Tag -> t -> Bool

Negation of ~==