From 279f04cb63e45ceb9a9df82540d5362565b8b37b Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Fri, 12 Aug 2022 22:53:06 +0100
Subject: Initial import

---
 src/Parser.hs | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 src/Parser.hs

(limited to 'src/Parser.hs')

diff --git a/src/Parser.hs b/src/Parser.hs
new file mode 100644
index 0000000..1c21700
--- /dev/null
+++ b/src/Parser.hs
@@ -0,0 +1,148 @@
+module Parser where
+
+import Ast
+import Data.Maybe (isJust)
+import Lexer
+import Text.Parsec
+import qualified Text.Parsec.Expr as E
+import Text.Parsec.String (Parser)
+
+binary s f assoc = E.Infix (reservedOp s >> return (BinOp f)) assoc
+
+opTable =
+  [ [ binary "*" Mul E.AssocLeft,
+      binary "/" Div E.AssocLeft
+    ],
+    [ binary "+" Plus E.AssocLeft,
+      binary "-" Minus E.AssocLeft
+    ]
+  ]
+
+expr :: Parser Expr
+expr = E.buildExpressionParser opTable factor
+
+number :: Parser Expr
+number = do
+  pos <- getPosition
+  n <- integer
+  return $ Num n pos
+
+variable :: Parser Expr
+variable = do
+  pos <- getPosition
+  var <- identifier
+  return $ Var var pos
+
+typ :: Parser Type
+typ = do
+  p <- identifier
+  return $ Type p
+
+typFn :: Parser Type
+typFn = do
+  p <- parens $ commaSep typ
+  r <- optionMaybe $ do
+    reserved "->"
+    typ
+  return $ FuncType p r
+
+type' :: Parser Type
+type' = do
+  try typFn
+    <|> typ <?> "type"
+
+arg :: Parser (String, Type, SourcePos)
+arg = do
+  pos <- getPosition
+  i <- identifier
+  _ <- colonSep <?> "\":\" before type"
+  t <- type' <?> "type"
+  return $ (i, t, pos)
+
+fdef :: Ident -> Bool -> SourcePos -> Parser Expr
+fdef ident priv pos = do
+  args <- parens $ commaSep arg
+  rtyp <-
+    optionMaybe
+      ( do
+          _ <- colonSep <?> "\":\" before type"
+          rtyp <- type' <?> "return type"
+          return $ rtyp
+      )
+  body <- braces $ many statement
+  return $ Func ident args rtyp body priv pos
+
+function :: Parser Expr
+function = do
+  pos <- getPosition
+  priv <- optionMaybe $ reserved "private"
+  reserved "def"
+  ident <- identifier
+  fdef ident (isJust priv) pos
+
+lambdaId :: SourcePos -> Ident
+lambdaId s =
+  "lambda" ++ "@" ++ show (sourceLine s) ++ "," ++ show (sourceColumn s)
+
+lambda :: Parser Expr
+lambda = do
+  pos <- getPosition
+  fdef (lambdaId pos) True pos
+
+return' :: Parser Expr
+return' = do
+  pos <- getPosition
+  reserved "return"
+  value <- optionMaybe expr
+  reservedOp ";"
+  return $ Return value pos
+
+call :: Parser Expr
+call = do
+  pos <- getPosition
+  ident <- try lambda <|> variable
+  args <- parens $ commaSep expr
+  return $ Call ident args pos
+
+factor :: Parser Expr
+factor =
+  try number
+    <|> try call
+    <|> try lambda
+    <|> try variable
+    <|> parens expr
+
+exprStmt :: Parser Expr
+exprStmt = do
+  e <- expr <|> factor
+  reservedOp ";"
+  return $ e
+
+statement :: Parser Expr
+statement = do
+  try exprStmt
+    <|> return'
+
+module' :: Parser Expr
+module' = do
+  pos <- getPosition
+  reserved "module"
+  ident <- identifier
+  return $ Module ident pos
+
+program :: Parser [Expr]
+program = do
+  m <- module'
+  n <-
+    many $ do
+      try function
+        -- TODO: variable decl
+        <|> statement <?> "statement"
+  return $ [m] ++ n
+
+parse :: Parser [Expr]
+parse = program
+
+parseFromFile p fname = do
+  input <- readFile fname
+  return (runParser p () fname input)
-- 
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