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|
-----------------------------------------------------------------------------
-- |
-- Module : ReadFirst
-- Copyright : 2004 Malcolm Wallace
-- Licence : LGPL
--
-- Maintainer : Malcolm Wallace <Malcolm.Wallace@cs.york.ac.uk>
-- Stability : experimental
-- Portability : All
--
-- Read the first file that matches in a list of search paths.
-----------------------------------------------------------------------------
module ReadFirst
( readFirst
) where
import IO (hPutStrLn, stderr)
import Directory (doesFileExist)
import List (intersperse)
import Position (Posn,directory)
import SymTab (SymTab,lookupST)
-- | Attempt to read the given file from any location within the search path.
-- The first location found is returned, together with the file content.
-- (The directory of the calling file is always searched first, then
-- the current directory, finally any specified search path.)
readFirst :: String -- ^ filename
-> Posn -- ^ inclusion point
-> [String] -- ^ search path
-> SymTab String -- ^ #defined symbols
-> IO ( FilePath -- ^ discovered file name, inc path
, String -- ^ file contents
)
readFirst name demand path syms =
try (cons dd (".":path))
where
dd = directory demand
cons x xs = if null x then xs else x:xs
realname = real name syms
try [] = do
hPutStrLn stderr ("Warning: Can't find file \""++realname
++"\" in directories\n\t"
++concat (intersperse "\n\t" (cons dd (".":path)))
++"\n Asked for by: "++show demand)
return ("missing file: "++realname,"")
try (p:ps) = do
let file = p++'/':realname
ok <- doesFileExist file
if not ok then try ps
else do content <- readFile file
return (file,content)
real :: String -> SymTab String -> String
real name syms = case name of
('"':ns) -> init ns
('<':ns) -> init ns
_ -> case lookupST name syms of
Nothing -> name
Just f -> real f syms
|
