/[james]/factorcss/FactorCSS.hs
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revision 61 by james, Sun Dec 19 22:10:41 2004 UTC revision 62 by james, Mon Dec 27 19:11:07 2004 UTC
# Line 1  Line 1 
1    -- Factor a CSS stylesheet
2    
3    import List
4  import Tokeniser  import Tokeniser
5  import Parser  import Parser
6  import CSS  import CSS
# Line 5  import CSS Line 8  import CSS
8  main = do  main = do
9          s <- getContents          s <- getContents
10  --      print (alexScanTokens s)  --      print (alexScanTokens s)
11  --      print (parser (alexScanTokens s))  --      (print . process . parser . alexScanTokens) s
12          putStr (unlines (show_stylesheet (parser (alexScanTokens s))))          (putStr . unlines . show_stylesheet . process .
13                            parser . alexScanTokens) s
14    
15    -- Process a Stylesheet.
16    process :: Stylesheet -> Stylesheet
17    process (Stylesheet charset imports stmts) =
18                    Stylesheet charset imports (process_stmts stmts)
19    
20    -- Process a list of Statements.
21    process_stmts :: [Statement] -> [Statement]
22    process_stmts stmts = (factor . filter is_ruleset) stmts ++
23                    (map process_media . filter is_media) stmts ++
24                    filter is_page stmts
25    
26    -- Process a Media Statement.
27    process_media :: Statement -> Statement
28    process_media (Media media stmts) = Media media (factor stmts)
29    
30    -- Factor a list of Ruleset Statements.
31    factor :: [Statement] -> [Statement]
32    factor = map implode_sel . groupBy eq_sel .
33                    sortBy cmp_sel .
34                    map implode_decl . groupBy eq_decl .
35                    sortBy cmp_decl . sortBy cmp_sel .
36                    concat . map explode
37    
38    -- Explode a Ruleset Statement into an equivalent list of Ruleset Statements
39    -- with one Selector and one Declaration per Ruleset.
40    --
41    -- For example (in CSS syntax),
42    --   explode "h1, em { color: red; background-color: blue }" =
43    --       "h1 { color: red }
44    --        h1 { background-color: blue }
45    --        em { color: red }
46    --        em { background-color: blue }"
47    --
48    -- [length (explode (Ruleset sels decls)) == length sels * length decls]
49    explode :: Statement -> [Statement]
50    explode (Ruleset sels decls) =
51                    concat (map (\s -> map (\d -> Ruleset [s] [d]) decls) sels)
52    
53    -- Compare two Ruleset Statements by the Selectors in each.
54    cmp_sel :: Statement -> Statement -> Ordering
55    cmp_sel (Ruleset sels0 decls0) (Ruleset sels1 decls1)
56            | a < b         = LT
57            | a == b        = EQ
58            | a > b         = GT
59            where   a = show_selectors sels0
60                    b = show_selectors sels1
61    
62    -- Compare two Ruleset Statements by the first Declaration in each.
63    cmp_decl :: Statement -> Statement -> Ordering
64    cmp_decl (Ruleset sels0 (decl0:decls0)) (Ruleset sels1 (decl1:decls1))
65            | a < b         = LT
66            | a == b        = EQ
67            | a > b         = GT
68            where   a = show_declaration decl0
69                    b = show_declaration decl1
70    
71    -- Compare two Ruleset Statements for equality by the Selectors in each.
72    eq_sel :: Statement -> Statement -> Bool
73    eq_sel z = (== EQ) . cmp_sel z
74    
75    -- Compare two Ruleset Statements for equality by the first declaration in each.
76    eq_decl :: Statement -> Statement -> Bool
77    eq_decl z = (== EQ) . cmp_decl z
78    
79    -- Implode a list of Ruleset Statements with equal lists of Selectors to a
80    -- single equivalent Ruleset Statement.
81    --
82    -- For example,
83    --   implode_sel "h1, em { color: red }
84    --        h1, em { background-color: blue }" =
85    --       "h1, em { color: red; background-color: blue }"
86    implode_sel :: [Statement] -> Statement
87    implode_sel ((Ruleset sels decls):stmts) =
88                    Ruleset sels (concat (decls:(map declarations stmts)))
89            where   declarations :: Statement -> [Declaration]
90                    declarations (Ruleset s d) = d
91    
92    -- Implode a list of Ruleset Statements with equal lists of Declarations to a
93    -- single equivalent Ruleset Statement.
94    --
95    -- For example,
96    --   implode_decl "h1 { color: red }
97    --        em { color: red }" =
98    --       "h1, em { color: red }"
99    implode_decl :: [Statement] -> Statement
100    implode_decl ((Ruleset sels decls):stmts) =
101                    Ruleset (concat (sels:(map selectors stmts))) decls
102            where   selectors :: Statement -> [Selector]
103                    selectors (Ruleset s d) = s
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