- [] -> Nothing
- (one:_) -> Just one
-
-arg_ok (NoArg _) rest arg = null rest
-arg_ok (HasArg _) rest arg = True
-arg_ok (SepArg _) rest arg = null rest
-arg_ok (Prefix _) rest arg = notNull rest
-arg_ok (PrefixPred p _) rest arg = notNull rest && p rest
-arg_ok (OptPrefix _) rest arg = True
-arg_ok (PassFlag _) rest arg = null rest
-arg_ok (AnySuffix _) rest arg = True
-arg_ok (AnySuffixPred p _) rest arg = p arg
+ [] -> Nothing
+ (one:_) -> Just one
+
+arg_ok :: OptKind t -> [Char] -> String -> Bool
+arg_ok (NoArg _) rest _ = null rest
+arg_ok (HasArg _) _ _ = True
+arg_ok (SepArg _) rest _ = null rest
+arg_ok (Prefix _) rest _ = notNull rest
+arg_ok (PrefixPred p _) rest _ = notNull rest && p (dropEq rest)
+arg_ok (OptIntSuffix _) _ _ = True
+arg_ok (IntSuffix _) _ _ = True
+arg_ok (OptPrefix _) _ _ = True
+arg_ok (PassFlag _) rest _ = null rest
+arg_ok (AnySuffix _) _ _ = True
+arg_ok (AnySuffixPred p _) _ arg = p arg
+
+parseInt :: String -> Maybe Int
+-- Looks for "433" or "=342", with no trailing gubbins
+-- n or =n => Just n
+-- gibberish => Nothing
+parseInt s = case reads s of
+ ((n,""):_) -> Just n
+ _ -> Nothing
+
+dropEq :: String -> String
+-- Discards a leading equals sign
+dropEq ('=' : s) = s
+dropEq s = s