Add many1Till to Combinators (#30)

* Add many1Till to Combinators

* Reimplement manyTill in terms of many1Till

Author: newlandsvalley

src/Text/Parsing/StringParser/Combinators.purs

@@ -23,6 +23,7 @@ module Text.Parsing.StringParser.Combinators
   , chainr1'
   , choice
   , manyTill
+  , many1Till
   , module Control.Lazy
   ) where
 
@@ -144,8 +145,11 @@ choice = foldl (<|>) (fail "Nothing to parse")
 
 -- | Parse values until a terminator.
 manyTill :: forall a end. Parser a -> Parser end -> Parser (List a)
-manyTill p end = scan
-  where
-  scan = (end *> pure Nil) <|> do x <- p
-                                  xs <- scan
-                                  pure (Cons x xs)
+manyTill p end = (end *> pure Nil) <|> many1Till p end
+
+-- | Parse values until the terminator matches, requiring at least one match.
+many1Till :: forall a end. Parser a -> Parser end -> Parser (List a)
+many1Till p end = do
+  x <- p
+  xs <- manyTill p end
+  pure (Cons x xs)

test/Main.purs

@@ -13,7 +13,7 @@ import Data.Unfoldable (replicate)
 
 import Test.Assert (assert', ASSERT, assert)
 import Text.Parsing.StringParser (Parser, runParser, try)
-import Text.Parsing.StringParser.Combinators (many1, endBy1, sepBy1, optionMaybe, many, chainl, fix, between)
+import Text.Parsing.StringParser.Combinators (many1, endBy1, sepBy1, optionMaybe, many, manyTill, many1Till, chainl, fix, between)
 import Text.Parsing.StringParser.Expr (Assoc(..), Operator(..), buildExprParser)
 import Text.Parsing.StringParser.String (anyDigit, eof, string, anyChar, regex)
 
@@ -86,3 +86,7 @@ main = do
   assert $ expectResult ('0':'1':'2':'3':'4':Nil) (many1 anyDigit) "01234/"
   assert $ expectResult ('5':'6':'7':'8':'9':Nil) (many1 anyDigit) "56789:"
   assert $ expectResult "aaaa" (regex "a+") "aaaab"
+  assert $ expectResult ("a":"a":"a":Nil)  (manyTill (string "a") (string "b")) "aaab"
+  assert $ expectResult Nil (manyTill (string "a") (string "b")) "b"
+  assert $ expectResult ("a":"a":"a":Nil)  (many1Till (string "a") (string "b")) "aaab"
+  assert $ parseFail (many1Till (string "a") (string "b")) "b"