core: Factor parseExactChar into the effect

src/Parser/Interface.md

@@ -235,8 +235,7 @@ Attempt to parse a specified character
 export
 parseExactChar : Char -> Parser Char
 parseExactChar c = do
-  pnote "Parsing exact char: \{show c}"
+  result <- parseExactChar' c
-  result <- parseChar (== c)
   case result of
     GotChar char => pure char
     GotError err => throwParseError "Got \{show err} Expected \{show c}"

src/Parser/ParserState.md

@@ -211,6 +211,7 @@ data ParserState : Type -> Type where
   -- TODO: Maybe add a ParseString that parses a string of characters as a 
   -- string using efficent slicing?
   ParseChar : (predicate : Char -> Bool) -> ParserState ParseCharResult
+  ParseExactChar : (char : Char) -> ParserState ParseCharResult
   ParseEoF : ParserState Bool
   Note : Lazy String -> ParserState ()
 ```
@@ -220,6 +221,7 @@ Show (ParserState t) where
   show Save = "Saving state"
   show (Load pi) = "Loading state \{show pi}"
   show (ParseChar predicate) = "Parsing char"
+  show (ParseExactChar char) = "Parsing char \{show char}"
   show ParseEoF = "Parsing EoF"
   show (Note _) = "Note"
 -->
@@ -245,6 +247,11 @@ parseChar : Has ParserState fs => (predicate : Char -> Bool)
   -> Eff fs ParseCharResult
 parseChar predicate = send $ ParseChar predicate 
 
+||| Parse a char by exact value
+export 
+parseExactChar' : Has ParserState fs => (chr : Char) -> Eff fs ParseCharResult
+parseExactChar' chr = send $ ParseExactChar chr
+
 ||| "Parse" the end of input, returning `True` if the parser state is currently
 ||| at the end of the input
 export
@@ -289,6 +296,9 @@ handleParserStateIO pi (ParseChar predicate) = do
     Just (Element next _) => do
       writeIORef pi.position $ MkIndex next
       pure $ GotChar char
+handleParserStateIO pi (ParseExactChar chr) = do
+  -- TODO: do this directly?
+  handleParserStateIO pi (ParseChar (== chr))
 handleParserStateIO pi ParseEoF = do
   pi <- readIORef pi
   readIORef pi.end_of_input
@@ -340,6 +350,7 @@ unPS pi (ParseChar predicate) =
         Just (Element next _) => 
           (GotChar char, {position := MkIndex next} pi)
       else (GotError char, pi)
+unPS pi (ParseExactChar chr) = unPS pi (ParseChar (== chr))
 unPS pi ParseEoF = (pi.end_of_input, pi)
 unPS pi (Note _) = ((), pi)