Added better error messages in parsers

2 files changed, 10 insertions, 4 deletions

diff --git a/Fractran/Parser.hs b/Fractran/Parser.hs
index 6d6cd86..95aa954 100644
--- a/Fractran/Parser.hs
+++ b/Fractran/Parser.hs
@@ -39,7 +39,8 @@ intPair = do
     return (numerator,denominator)
 
 
-slash = char '/'
+slash  =  char '/'
+      <?> "slash character"
 
 
 initVal = do
@@ -59,7 +60,8 @@ positiveNumber = do
     return (read (firstDigit:rest))
 
 
-nonZeroDigit = oneOf "123456789"
+nonZeroDigit  =  oneOf "123456789"
+             <?> "non-zero digit"
 
 
 whiteSpace = many (oneOf "\t\n\r ")
diff --git a/Thue/Parser.hs b/Thue/Parser.hs
index d7b0719..2ee41ae 100644
--- a/Thue/Parser.hs
+++ b/Thue/Parser.hs
@@ -49,7 +49,8 @@ rule = do
 
 
 separatorLine = whiteSpace >> separator >> whiteSpace >> eol
-separator = string "::="
+separator  =  string "::="
+          <?> "rule separator"
 
 
 initialState = do
@@ -62,12 +63,14 @@ ruleState = some ruleStateChar
 
 ruleStateChar  =  noneOf "\n\r:"
 	          <|> try (char ':' >> notFollowedBy (string ":=") >> return ':')
+	          <?> "state character"
 
 
 state = many stateChar
 
 
-stateChar = noneOf "\n\r"
+stateChar  =  noneOf "\n\r"
+          <?> "state character"
 
 
 whiteSpace = many (oneOf "\t ")
@@ -77,4 +80,5 @@ eol  =  try (string "\r\n")
     <|> try (string "\n\r")
     <|> try (string "\r")
     <|> try (string "\n")
+    <?> "end of line"