WIP takeMany

Author: jamesdbrock

src/Parsing/Combinators.purs

@@ -55,6 +55,7 @@ module Parsing.Combinators
   , manyTill_
   , many1Till
   , many1Till_
+  , manyFromTo
   , skipMany
   , skipMany1
   , sepBy
@@ -440,3 +441,43 @@ manyTill_ p end = tailRecM go Nil
         do
           x <- p
           pure (Loop (x : xs))
+
+
+-- | Repeat the phase like *many* at least *N* times, but no more than *M*
+-- | times.
+-- |
+-- | Returns the list of results and the length of the list.
+-- |
+-- | `manyFromTo n n` is equivalent to `replicateA n`.
+manyFromTo :: forall s m a. Int -> Int -> ParserT s m a -> ParserT s m (Tuple Int (List a))
+manyFromTo from to p =
+  if from > to then
+    pure (Tuple 0 Nil)
+  else
+    tailRecM go (Tuple 0 Nil)
+  where
+  go (Tuple i xs) =
+    if i >= to then
+      pure (Done (Tuple i (reverse xs)))
+    else
+      ( do
+          x <- p
+          pure (Loop (Tuple (i+1) (x : xs)))
+      )
+      <|>
+      ( if i >= from
+          then
+            pure (Done (Tuple i (reverse xs)))
+          else
+            fail "manyFromTo expected more"
+      )
+
+-- | Repeat the parse phrases and collect them in a list until the supplied
+-- | predicate returns false.
+-- |
+-- | The predicate takes the number of phrases already parsed, and the
+-- | result of the most recent parse.
+-- |
+-- | Returns the list of results and the length of the list.
+-- while :: forall s m a. (Int -> a -> m Boolean) -> ParserT s m a -> ParserT s m (Tuple Int (List a))
+-- while predicate p =

test/Main.purs

@@ -34,7 +34,7 @@ import Effect.Console (log, logShow)
 import Effect.Unsafe (unsafePerformEffect)
 import Node.Process (lookupEnv)
 import Parsing (ParseError(..), Parser, ParserT, Position(..), consume, fail, initialPos, parseErrorMessage, parseErrorPosition, position, region, runParser)
-import Parsing.Combinators (between, chainl, chainl1, chainr, chainr1, choice, endBy, endBy1, lookAhead, many, many1, many1Till, many1Till_, manyTill, manyTill_, notFollowedBy, optionMaybe, sepBy, sepBy1, sepEndBy, sepEndBy1, skipMany, skipMany1, try, (<?>), (<??>), (<~?>))
+import Parsing.Combinators (between, chainl, chainl1, chainr, chainr1, choice, endBy, endBy1, lookAhead, many, many1, many1Till, many1Till_, manyFromTo, manyTill, manyTill_, notFollowedBy, optionMaybe, sepBy, sepBy1, sepEndBy, sepEndBy1, skipMany, skipMany1, try, (<?>), (<??>), (<~?>))
 import Parsing.Expr (Assoc(..), Operator(..), buildExprParser)
 import Parsing.Language (haskellDef, haskellStyle, javaStyle)
 import Parsing.String (anyChar, anyCodePoint, anyTill, char, eof, match, regex, rest, satisfy, string, takeN)
@@ -1006,3 +1006,22 @@ main = do
           rmap fst <$> splitCap "((🌼)) (()())" (match balancedParens)
     , expected: NonEmptyList $ Right "((🌼))" :| Left " " : Right "(()())" : Nil
     }
+
+  log "\nTESTS manyFromTo\n"
+
+  assertEqual' "manyFromTo 1"
+    { actual: runParser "aaab" $ manyFromTo 0 3 (char 'a')
+    , expected: Right (Tuple 3 ('a':'a':'a':Nil))
+    }
+  assertEqual' "manyFromTo 2"
+    { actual: runParser "aaaa" $ manyFromTo 0 3 (char 'a')
+    , expected: Right (Tuple 3 ('a':'a':'a':Nil))
+    }
+  assertEqual' "manyFromTo 3"
+    { actual: runParser "b" $ manyFromTo 0 3 (char 'a')
+    , expected: Right (Tuple 0 (Nil))
+    }
+  assertEqual' "manyFromTo 4"
+    { actual: lmap parseErrorPosition $ runParser "ab" $ manyFromTo 3 3 (char 'a')
+    , expected: Left (Position {index:1,line:1,column:2})
+    }