From f5c552adf7a836ed8fb22d0141fdb6a0e8454149 Mon Sep 17 00:00:00 2001
From: Philippe Pittoli <karchnu@karchnu.fr>
Date: Wed, 10 Jan 2024 04:06:23 +0100
Subject: [PATCH] Most of the parser just got implemented!

---
 spago.dhall     |  1 +
 src/Main.purs   |  5 +++++
 src/Parser.purs | 58 +++++++++++++++++++++++++++++++++++++++++--------
 3 files changed, 55 insertions(+), 9 deletions(-)

diff --git a/spago.dhall b/spago.dhall
index a5cc9fb..5282eda 100644
--- a/spago.dhall
+++ b/spago.dhall
@@ -16,6 +16,7 @@ to generate this file without the comments in this block.
   , "console"
   , "control"
   , "effect"
+  , "integers"
   , "maybe"
   , "prelude"
   , "strings"
diff --git a/src/Main.purs b/src/Main.purs
index aae686d..786db45 100644
--- a/src/Main.purs
+++ b/src/Main.purs
@@ -47,6 +47,11 @@ main = do
     Just (Tuple x y) -> show x <> " " <> show y
     Nothing -> "failed"
 
+  log $ "parsing ident (all first alphanum) in 'ab123-blah' (ident): " <>
+    case parse ident "ab123-blah" of
+      Just (Tuple x y) -> show x <> " " <> show y
+      Nothing -> "failed"
+
 -- JUST WORKS
 --  isffound $ parse isf "fable"
 --  isffound $ parse isf "f"
diff --git a/src/Parser.purs b/src/Parser.purs
index 3205729..c669ecf 100644
--- a/src/Parser.purs
+++ b/src/Parser.purs
@@ -2,10 +2,12 @@ module Parser where
 
 import Prelude
 
-import Control.Alt (class Alt)
+import Data.Int as Int
+
+import Control.Alt (class Alt, (<|>))
 import Control.Plus (class Plus, empty)
 import Control.Alternative (class Alternative)
--- TODO: import Control.Lazy (class Lazy)
+import Control.Lazy (class Lazy)
 
 import Data.Array as A
 import Data.Maybe (Maybe(..))
@@ -61,8 +63,8 @@ instance plusParser :: Plus Parser where
 instance alternativeParser :: Alternative Parser
 
 -- TODO: Control.Lazy instance
---instance lazyParser :: Lazy Parser (Array a) where
---  defer 
+instance lazyParser :: Lazy (Parser a) where
+  defer f = Parser \str -> parse (f unit) str
 
 -- Generic parsing functions.
 
@@ -113,11 +115,49 @@ string str = case A.uncons (toCharArray str) of
                                    rest <- string (fromCharArray xs)
                                    pure (concat c rest)
 
--- TODO: A.many requires an instance of Control.Lazy class.
---ident :: Parser String
---ident = do x  <- lower
---           xs <- A.many alphanum
---           pure (fromCharArray $ A.cons x xs)
+ident :: Parser String
+ident = do x  <- lower
+           xs <- A.many alphanum
+           pure (fromCharArray $ A.cons x xs)
+
+nat :: Parser Int
+nat = do xs <- A.some digit
+         case Int.fromString (fromCharArray xs) of
+           Nothing -> empty
+           Just x -> pure x
+
+int :: Parser Int
+int = do _ <- char '-'
+         n <- nat
+         pure (-n)
+       <|> nat
+
+-- Handling spacing
+
+isSpace :: Char -> Boolean
+isSpace c = A.any (\v -> v == c) [' ', '\t', ' ', '\r', '\n']
+
+space :: Parser Unit
+space = do _ <- A.many (sat isSpace)
+           pure unit
+
+token :: forall a. Parser a -> Parser a
+token p = do space
+             v <- p
+             _ <- space
+             pure v
+
+identifier :: Parser String
+identifier = token ident
+
+natural :: Parser Int
+natural = token nat
+
+integer :: Parser Int
+integer = token int
+
+symbol :: String -> Parser String
+symbol xs = token (string xs)
 
 -- TODO: try orElse
 --try :: Parser a -> Parser a