Change relaxed expr parser implementationexperimental/relaxed-expr-parser-alt

Debatable whether better or worse.

2 files changed, 9 insertions, 15 deletions

diff --git a/src/Language/SimpleShell/Parser.hs b/src/Language/SimpleShell/Parser.hs
index be16c9f..d75602b 100644
--- a/src/Language/SimpleShell/Parser.hs
+++ b/src/Language/SimpleShell/Parser.hs
@@ -4,7 +4,6 @@ module Language.SimpleShell.Parser
   ( Parser
   , lexeme
   , symbol
-  , commentFirstChars
   , lookupVar
   , lookupFun
   , declareVars
@@ -51,17 +50,12 @@ initContext = Context
   }
 
 
--- Must be kept in sync with 'commentFirstChars'.
 sc :: Parser ()
 sc = L.space
   space1
   (L.skipLineComment "//")
   (L.skipBlockComment "/*" "*/")
 
--- | List of all characters that may start a comment.
-commentFirstChars :: [Char]
-commentFirstChars = "/"
-
 lexeme :: Parser a -> Parser a
 lexeme = L.lexeme sc
 
diff --git a/src/Language/SimpleShell/Parser/Expr.hs b/src/Language/SimpleShell/Parser/Expr.hs
index cabf522..0f2f6c9 100644
--- a/src/Language/SimpleShell/Parser/Expr.hs
+++ b/src/Language/SimpleShell/Parser/Expr.hs
@@ -15,7 +15,6 @@ import Language.SimpleShell.Parser
   ( Parser
   , lexeme
   , symbol
-  , commentFirstChars
   , lookupVar
   , lookupFun
   )
@@ -32,7 +31,7 @@ import Control.Monad (void)
 import Control.Monad.Combinators (manyTill)
 import Data.Foldable (asum)
 import Data.Text (Text)
-import Text.Megaparsec (takeWhile1P, oneOf, many)
+import Text.Megaparsec (anySingleBut, many)
 import Text.Megaparsec.Char (char)
 import qualified Text.Megaparsec.Char.Lexer as L (charLiteral, decimal)
 
@@ -67,16 +66,17 @@ strongTermP_
     --    * parentheses
     --    * string literals
     --    * comments
+    --    - Thus, `takeWhile1P` is dangerous.
+    --  * This is hardly the most efficient implementation.
+    --    * A more efficient implementation would use `takeWhile1P` to parse
+    --      large chunks of input, but--as noted above--that is dangerous;
+    --      i.e., non-trivial (albeit not really hard) to do correctly.
 
     tok :: Parser ()
     tok
-       =  void strLitP
-      <|> symbol "(" *> void (many tok) <* symbol ")"
-      <|> void (lexeme $ takeWhile1P Nothing isBoring)
-      <|> void (lexeme $ oneOf commentFirstChars)
-      where
-        isBoring :: Char -> Bool
-        isBoring = not . (`elem` "()\"" ++ commentFirstChars)
+       =  strongTermP_
+      <|> void nameP    -- function names; for efficiency only
+      <|> void (lexeme $ anySingleBut ')')  -- operators (i.a.; catchall)
 
 
 -- | Parse "strong" term with fixed type.