Merge pull request #47 from mlang/Discard

Avoid Discard constraints

Author: paf31

src/Text/Parsing/Parser/Combinators.purs

@@ -52,20 +52,15 @@ infix 3 asErrorMessage as <??>
 -- | parens = between (string "(") (string ")")
 -- | ```
 between :: forall m s a open close. Monad m => ParserT s m open -> ParserT s m close -> ParserT s m a -> ParserT s m a
-between open close p = do
-  open
-  a <- p
-  close
-  pure a
+between open close p = open *> p <* close
 
 -- | Provide a default result in the case where a parser fails without consuming input.
 option :: forall m s a. Monad m => a -> ParserT s m a -> ParserT s m a
 option a p = p <|> pure a
 
 -- | Optionally parse something, failing quietly.
 optional :: forall m s a. Monad m => ParserT s m a -> ParserT s m Unit
-optional p = (do p
-                 pure unit) <|> pure unit
+optional p = (void p) <|> pure unit
 
 -- | pure `Nothing` in the case where a parser fails without consuming input.
 optionMaybe :: forall m s a. Monad m => ParserT s m a -> ParserT s m (Maybe a)
@@ -99,9 +94,7 @@ sepBy p sep = sepBy1 p sep <|> pure Nil
 sepBy1 :: forall m s a sep. Monad m => ParserT s m a -> ParserT s m sep -> ParserT s m (List a)
 sepBy1 p sep = do
   a <- p
-  as <- many $ do
-    sep
-    p
+  as <- many $ sep *> p
   pure (a : as)
 
 -- | Parse phrases delimited and optionally terminated by a separator.
@@ -112,23 +105,17 @@ sepEndBy p sep = sepEndBy1 p sep <|> pure Nil
 sepEndBy1 :: forall m s a sep. Monad m => ParserT s m a -> ParserT s m sep -> ParserT s m (List a)
 sepEndBy1 p sep = do
   a <- p
-  (do sep
+  (do _ <- sep
       as <- sepEndBy p sep
       pure (a : as)) <|> pure (singleton a)
 
 -- | Parse phrases delimited and terminated by a separator, requiring at least one match.
 endBy1 :: forall m s a sep. Monad m => ParserT s m a -> ParserT s m sep -> ParserT s m (List a)
-endBy1 p sep = some $ do
-  a <- p
-  sep
-  pure a
+endBy1 p sep = some $ p <* sep
 
 -- | Parse phrases delimited and terminated by a separator.
 endBy :: forall m s a sep. Monad m => ParserT s m a -> ParserT s m sep -> ParserT s m (List a)
-endBy p sep = many $ do
-  a <- p
-  sep
-  pure a
+endBy p sep = many $ p <* sep
 
 -- | Parse phrases delimited by a right-associative operator.
 -- |
@@ -189,9 +176,7 @@ notFollowedBy p = try $ (try p *> fail "Negated parser succeeded") <|> pure unit
 manyTill :: forall s a m e. Monad m => ParserT s m a -> ParserT s m e -> ParserT s m (List a)
 manyTill p end = scan
   where
-    scan = (do
-              end
-              pure Nil)
+    scan = (end $> Nil)
        <|> (do
               x <- p
               xs <- scan

src/Text/Parsing/Parser/String.purs

@@ -79,9 +79,7 @@ whiteSpace = do
 
 -- | Skip whitespace characters.
 skipSpaces :: forall s m. (StringLike s, Monad m) => ParserT s m Unit
-skipSpaces = do
-  whiteSpace
-  pure unit
+skipSpaces = void whiteSpace
 
 -- | Match one of the characters in the array.
 oneOf :: forall s m. (StringLike s, Monad m) => Array Char -> ParserT s m Char

src/Text/Parsing/Parser/Token.purs

@@ -414,7 +414,7 @@ makeTokenParser (LanguageDef languageDef)
 
     stringEscape :: ParserT String m (Maybe Char)
     stringEscape = do
-        char '\\'
+        _ <- char '\\'
         (escapeGap $> Nothing) <|> (escapeEmpty $> Nothing) <|> (Just <$> escapeCode)
 
     escapeEmpty :: ParserT String m Char
@@ -430,7 +430,7 @@ makeTokenParser (LanguageDef languageDef)
 
     charControl :: ParserT String m Char
     charControl = do
-        char '^'
+        _ <- char '^'
         code <- upper
         pure <<< fromCharCode $ toCharCode code - toCharCode 'A' + 1
 
@@ -537,7 +537,7 @@ makeTokenParser (LanguageDef languageDef)
 
     fraction :: ParserT String m Number
     fraction = "fraction" <??> do
-        char '.'
+        _ <- char '.'
         digits <- Array.some digit <?> "fraction"
         maybe (fail "not digit") pure $ foldr op (Just 0.0) digits
       where
@@ -549,7 +549,7 @@ makeTokenParser (LanguageDef languageDef)
 
     exponent' :: ParserT String m Number
     exponent' = "exponent" <??> do
-        oneOf ['e', 'E']
+        _ <- oneOf ['e', 'E']
         f <- sign
         e <- decimal <?> "exponent"
         pure $ power (f e)
@@ -604,7 +604,7 @@ makeTokenParser (LanguageDef languageDef)
       where
         go :: ParserT String m Unit
         go = do
-            string name
+            _ <- string name
             notFollowedBy languageDef.opLetter <?> "end of " <> name
 
     operator :: ParserT String m String