+ Added a 'substitute' function to Shared.hs. This is a generic

  list function that can be used to substitute one substring
  for another in a string, like 'gsub' except without regular
  expressions.
+ Use 'substitute' instead of 'gsub' in the LaTeX writer.  This
  avoids what appears to be a bug in Text.Regex, whereby "\\^"
  matches "\350".  There seems to be a slight speed improvement
  as well.  (Note:  If this works, it would be good to replace
  other uses of gsub that don't employ regexs with 'substitute'.) 


git-svn-id: https://pandoc.googlecode.com/svn/trunk@500 788f1e2b-df1e-0410-8736-df70ead52e1b

2 files changed, 18 insertions, 8 deletions

diff --git a/src/Text/Pandoc/Shared.hs b/src/Text/Pandoc/Shared.hs
index 8ee990827..adaffb9da 100644
--- a/src/Text/Pandoc/Shared.hs
+++ b/src/Text/Pandoc/Shared.hs
@@ -31,6 +31,7 @@ module Text.Pandoc.Shared (
                      -- * List processing
                      splitBy,
                      splitByIndices,
+                     substitute,
                      -- * Text processing
                      gsub,
                      joinWithSep,
@@ -79,8 +80,8 @@ import Text.Pandoc.Entities ( decodeEntities, encodeEntities, characterEntity )
 import Text.Regex ( matchRegexAll, mkRegex, subRegex, Regex )
 import Text.PrettyPrint.HughesPJ as PP ( text, char, (<>), ($$), nest, Doc, 
                                          isEmpty )
-import Char ( toLower )
-import List ( find, groupBy )
+import Data.Char ( toLower )
+import Data.List ( find, groupBy, isPrefixOf )
 
 -- | Parse a string with a given parser and state.
 readWith :: GenParser Char ParserState a      -- ^ parser
@@ -288,6 +289,15 @@ removeTrailingSpace = reverse . removeLeadingSpace . reverse
 stripFirstAndLast str =
   drop 1 $ take ((length str) - 1) str
 
+-- | Replace each occurrence of one sublist in a list with another.
+substitute :: (Eq a) => [a] -> [a] -> [a] -> [a]
+substitute _ _ [] = []
+substitute [] _ lst = lst
+substitute target replacement lst = 
+    if isPrefixOf target lst
+       then replacement ++ (substitute target replacement $ drop (length target) lst)
+       else (head lst):(substitute target replacement $ tail lst)
+
 -- | Split list into groups separated by sep.
 splitBy :: (Eq a) => a -> [a] -> [[a]]
 splitBy _ [] = []
diff --git a/src/Text/Pandoc/Writers/LaTeX.hs b/src/Text/Pandoc/Writers/LaTeX.hs
index db7af223d..2badf2f24 100644
--- a/src/Text/Pandoc/Writers/LaTeX.hs
+++ b/src/Text/Pandoc/Writers/LaTeX.hs
@@ -78,12 +78,12 @@ latexHeader notes options (Meta title authors date) =
 escapeBrackets  = backslashEscape "{}"
 escapeSpecial   = backslashEscape "$%&~_#"
 
-escapeBackslash = gsub "\\\\" "\\\\textbackslash{}" 
-fixBackslash    = gsub "\\\\textbackslash\\\\\\{\\\\\\}" "\\\\textbackslash{}"
-escapeHat       = gsub "\\^" "\\\\^{}"
-escapeBar       = gsub "\\|" "\\\\textbar{}"
-escapeLt        = gsub "<" "\\\\textless{}"
-escapeGt        = gsub ">" "\\\\textgreater{}"
+escapeBackslash = substitute "\\" "\\textbackslash{}" 
+fixBackslash    = substitute "\\textbackslash\\{\\}" "\\textbackslash{}"
+escapeHat       = substitute "^" "\\^{}"
+escapeBar       = substitute "|" "\\textbar{}"
+escapeLt        = substitute "<" "\\textless{}"
+escapeGt        = substitute ">" "\\textgreater{}"
 
 -- | Escape string for LaTeX
 stringToLaTeX :: String -> String