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Yahoo! search interface: Difference between revisions
Added Haskell
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Button:Go,Area:browser window,Inputbox:searchbox>elephants,Button:Search</lang>
=={{header|Haskell}}==
Haskell is not an object oriented language, so this example does not implement an object class.
However, it can be interesting as an example of how HTML source code can be parsed using the Parsec library.
<lang Haskell>import Network.HTTP
import Text.Parsec
data YahooSearchItem = YahooSearchItem {
itemUrl, itemTitle, itemContent :: String }
data YahooSearch = YahooSearch {
searchQuery :: String,
searchPage :: Int,
searchItems :: [YahooSearchItem] }
-- URL for Yahoo! searches, without giving a page number
yahooUrl = "http://search.yahoo.com/search?p="
-- make an HTTP request and return a YahooSearch
yahoo :: String -> IO YahooSearch
yahoo q = simpleHTTP (getRequest $ yahooUrl ++ q) >>=
getResponseBody >>= return . YahooSearch q 1 . items
-- get some results and return the next page of results
next :: YahooSearch -> IO YahooSearch
next (YahooSearch q p _) =
simpleHTTP (getRequest $
-- add the page number to the search
yahooUrl ++ q ++ "&b=" ++ show (p + 1)) >>=
getResponseBody >>= return . YahooSearch q (p + 1) . items
printResults :: YahooSearch -> IO ()
printResults (YahooSearch q p items) = do
putStrLn $ "Showing Yahoo! search results for query: " ++ q
putStrLn $ "Page: " ++ show p
putChar '\n'
mapM_ printOne items
where
printOne (YahooSearchItem itemUrl itemTitle itemContent) = do
putStrLn $ "URL : " ++ itemUrl
putStrLn $ "Title : " ++ itemTitle
putStrLn $ "Abstr : " ++ itemContent
putChar '\n'
urlTag, titleTag, contentTag1, contentTag2, ignoreTag,
ignoreText :: Parsec String () String
-- parse a tag containing the URL of a search result
urlTag = do { string "<a id=\"link-";
many digit; string "\" class=\"yschttl spt\" href=\"";
url <- manyTill anyChar (char '"'); manyTill anyChar (char '>');
return url }
-- the title comes after the URL tag, so parse it first, discard it
-- and get the title text
titleTag = do { urlTag; manyTill anyChar (try (string "</a>")) }
-- parse a tag containing the description of the search result
-- the tag can be named "sm-abs" or "abstr"
contentTag1 = do { string "<div class=\"sm-abs\">";
manyTill anyChar (try (string "</div>")) }
contentTag2 = do { string "<div class=\"abstr\">";
manyTill anyChar (try (string "</div>")) }
-- parse a tag and discard it
ignoreTag = do { char ('<'); manyTill anyChar (char '>');
return "" }
-- parse some text and discard it
ignoreText = do { many1 (noneOf "<"); return "" }
-- return only non-empty strings
nonempty :: [String] -> Parsec String () [String]
nonempty xs = return [ x | x <- xs, not (null x) ]
-- a template to parse a whole source file looking for items of the
-- same class
parseCategory x = do
res <- many x
eof
nonempty res
urls, titles, contents :: Parsec String () [String]
-- parse HTML source looking for URL tags of the search results
urls = parseCategory url where
url = (try urlTag) <|> ignoreTag <|> ignoreText
-- parse HTML source looking for titles of the search results
titles = parseCategory title where
title = (try titleTag) <|> ignoreTag <|> ignoreText
-- parse HTML source looking for descriptions of the search results
contents = parseCategory content where
content = (try contentTag1) <|> (try contentTag2) <|>
ignoreTag <|> ignoreText
-- parse the HTML source three times looking for URL, title and
-- description of all search results and return them as a list of
-- YahooSearchItem
items :: String -> [YahooSearchItem]
items q =
let ignoreOrKeep = either (const []) id
us = ignoreOrKeep $ parse urls "" q
ts = ignoreOrKeep $ parse titles "" q
cs = ignoreOrKeep $ parse contents "" q
in [ YahooSearchItem { itemUrl = u, itemTitle = t, itemContent = c } |
(u, t, c) <- zip3 us ts cs ]
</lang>
Simple invocation from GHCi: <pre>yahoo "Rosetta%20code" >>= printResults</pre>. Notice that spaces must be expressed as "%20", because spaces are not allowed in URLs.
==Icon and {{header|Unicon}}==
The following uses the Unicon pre-processor and messaging extensions and won't run under Icon without significant modification.
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