Add anyDigit

Author: garyb

src/Text/Parsing/StringParser/String.purs

@@ -1,8 +1,14 @@
-module Text.Parsing.StringParser.String where
+module Text.Parsing.StringParser.String
+  ( eof
+  , anyChar
+  , anyDigit
+  , string
+  ) where
 
-import Data.Maybe
-import Data.String (charAt, fromChar, length, take, indexOf')
+import Data.Maybe (Maybe(..))
+import Data.String (charAt, fromChar, length, indexOf')
 import Text.Parsing.StringParser
+import qualified Data.String.Regex as Rx
 
 eof :: Parser Unit
 eof = Parser (\s fc sc -> case s of
@@ -15,6 +21,18 @@ anyChar = Parser (\s fc sc -> case s of
     Just chr -> sc (fromChar chr) { str: str, pos: i + 1 }
     Nothing -> fc i (ParseError "Unexpected EOF"))
 
+anyDigit :: Parser String
+anyDigit = Parser \{ str: str, pos: i } fc sc -> case charAt i str of
+  Just chr ->
+    let chrS = fromChar chr
+    in if Rx.test rxDigit chrS
+       then sc chrS { str: str, pos: i + 1 }
+       else fc i (ParseError "Expected digit")
+  Nothing -> fc i (ParseError "Unexpected EOF")
+
+rxDigit :: Rx.Regex
+rxDigit = Rx.regex "^[0-9]" Rx.noFlags
+
 string :: String -> Parser String
 string nt = Parser (\s fc sc -> case s of
   { str = str, pos = i } | indexOf' nt i str == i -> sc nt { str: str, pos: i + length nt }