blob: 2eb090131825948ac2a8a371d63af5c53d478fef (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
----------------------------------------------------------------------
-- |
-- Maintainer : PL
-- Stability : (stable)
-- Portability : (portable)
--
-- > CVS $Date: 2005/04/11 13:52:49 $
-- > CVS $Author: peb $
-- > CVS $Revision: 1.1 $
--
-- CFG formalism
-----------------------------------------------------------------------------
module GF.Formalism.CFG where
import GF.Formalism.Utilities
import GF.Infra.Print
import GF.Data.Assoc (accumAssoc)
import GF.Data.SortedList (groupPairs)
import GF.Data.Utilities (mapSnd)
------------------------------------------------------------
-- type definitions
type CFGrammar c n t = [CFRule c n t]
data CFRule c n t = CFRule c [Symbol c t] n
deriving (Eq, Ord, Show)
type CFChart c n t = CFGrammar (Edge c) n t
------------------------------------------------------------
-- building syntax charts from grammars
grammar2chart :: (Ord n, Ord e) => CFGrammar e n t -> SyntaxChart n e
grammar2chart cfchart = accumAssoc groupPairs $
[ (lhs, (name, filterCats rhs)) |
CFRule lhs rhs name <- cfchart ]
----------------------------------------------------------------------
-- pretty-printing
instance (Print n, Print c, Print t) => Print (CFRule c n t) where
prt (CFRule cat rhs name) = prt name ++ " : " ++ prt cat ++
( if null rhs then ""
else " --> " ++ prtSep " " rhs )
prtList = prtSep "\n"
|
