From fd638c3c6fe7db6098db382ee4d7daefbb7ab07b Mon Sep 17 00:00:00 2001
From: ik1g19 <ik1g19@soton.ac.uk>
Date: Sun, 3 Jan 2021 22:38:24 +0000
Subject: [PATCH] progress on challenge 4
---
cw/src/Challenges.hs | 63 +++++++++++++++++++++++++++++++-------------
1 file changed, 45 insertions(+), 18 deletions(-)
diff --git a/cw/src/Challenges.hs b/cw/src/Challenges.hs
index cca5fb0..b53ad3a 100644
--- a/cw/src/Challenges.hs
+++ b/cw/src/Challenges.hs
@@ -278,8 +278,8 @@ prettyPrint (LamDef ms e) = exprBrackets e
--applies brackets to expr if needed
exprBrackets :: LamExpr -> String
-exprBrackets e | expr str == e = str --omit brackets
- | otherwise = "(" + str ++ ")" --include brackets
+exprBrackets e | fst (head (parse expr str)) == e = str --omit brackets
+ | otherwise = "(" ++ str ++ ")" --include brackets
where
str = exprToStr e
@@ -318,36 +318,63 @@ ex3'4 = LamDef [ ("F", LamAbs 1 (LamVar 1) ) ] (LamAbs 2 (LamApp (LamAbs 1 (LamV
parseLamMacro :: String -> Maybe LamMacroExpr
-parseLamMacro _ = Nothing
+parseLamMacro str | parsed == [] = Nothing
+ | otherwise = Just parsed
+ where
+ parsed = fst (head (parse (macroExpr []) str)) --HEAD WILL NOT WORK
+
+
+macroExpr :: [ (String,LamExpr) ] -> Parser LamMacroExpr
+macroExpr ms = do string "def"
+ name <- token macroName
+ symbol "="
+ e <- token expr
+ token $ string "in"
+ macros <- macroExpr $ ms ++ [(name,e)]
+ return $ macros
+ <|> do e <- token expr
+ return $ LamDef ms e
-macroExpr :: Parse LamMacroExpr
-macroExpr = do string "def"
- name <- token macroName
- symbol "="
- e <- token expr
- string "in"
- macro <- many macroExpr
- return $ LamDef [(name,e)]
+
+
+-- macroExpr :: Parse LamMacroExpr
+-- macroExpr = do string "def"
+-- name <- token macroName
+-- symbol "="
+-- e <- token expr
+-- token $ string "in"
+-- macros <- macroLoop
+-- return $ LamDef macros
+-- where
+-- macroLoop :: Parse [(String,LamExpr)]
+-- macroLoop = do string "def"
+-- name <- token macroName
+-- symbol "="
+-- e <- token expr
+-- token $ string "in"
+-- ms <- many macroExpr
+-- return ((name,e):ms) <|>
+-- do {e <- token expr;return []}
expr :: Parser LamExpr
-expr = do {x <- var; return $ LamVar x} <|>
+expr = do {x <- var; return $ LamVar x}
- do {name <- macroName;return $ LamMacro name} <|>
+ <|> do {name <- macroName;return $ LamMacro name}
- do e1 <- expr
+ <|> do e1 <- expr
space
e2 <- expr
- return $ LamApp e1 e2 <|>
+ return $ LamApp e1 e2
- do char '\'
+ <|> do char '\\'
x <- var
symbol "->"
e <- expr
- return $ LamAbs x e <|>
+ return $ LamAbs x e
- do char '('
+ <|> do char '('
e <- token expr
char ')'
return e
--
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