From 89bb18a1ad21ad747305230ea6d1c18e181c228b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Baltasar=20S=C3=A1nchez=20E?= <bse@naringas.info>
Date: Sat, 6 May 2023 20:58:03 -0600
Subject: [PATCH] ternary expressions added. seem ok

---
 exp.lox        |  4 ++++
 expressions.py |  8 ++++++++
 interpreter.py |  7 +++++++
 parser.py      | 27 +++++++++++++++++++++++----
 scanner.py     |  3 +++
 src.lox        | 12 +++++++-----
 statements.py  |  2 +-
 7 files changed, 53 insertions(+), 10 deletions(-)
 create mode 100644 exp.lox

diff --git a/exp.lox b/exp.lox
new file mode 100644
index 0000000..e8a8b61
--- /dev/null
+++ b/exp.lox
@@ -0,0 +1,4 @@
+(13 > (5 * 3 + 9));
+123 != 12312 + (2.3 == 123) * 9.12
+// asf asf
+1+2-3*4/5  //  saywha
diff --git a/expressions.py b/expressions.py
index 29118c0..221c43d 100644
--- a/expressions.py
+++ b/expressions.py
@@ -32,6 +32,12 @@ class Unary(Expr):
 class Variable(Expr):
 	name: Token  #identifier
 
+@dataclass
+class Ternary(Expr):
+	comparison: Expr
+	left: Expr  # true evaluation, comparison must be boolean
+	right: Expr
+
 
 class AstPrinter(Visitor):
 	"""only good at printing out (and making strings) from binary expressions"""
@@ -65,6 +71,8 @@ def visitUnary(self, expr):
 	def visitBinary(self, expr):
 		return self.parensiffy(expr.op.lexeme, expr.left, expr.right)
 
+	def visitTernary(self, expr):
+		return f'if [{expr.comparison}]; then [{expr.left}]; else [{expr.right}]'
 	"""
 	def visitExpr(self, expr):
 		return self.parensiffy(expr.expr)
diff --git a/interpreter.py b/interpreter.py
index 1c41d73..e3ac530 100644
--- a/interpreter.py
+++ b/interpreter.py
@@ -25,6 +25,13 @@ def visitStmtPrint(self, stmt):
 		print(val)
 		return val
 
+	def visitStmtVar(self, stmt):
+		"""
+		stmt.name
+		stmt.initializer
+		"""
+		...
+
 	def visitLiteral(self, expr):
 		return expr.value
 
diff --git a/parser.py b/parser.py
index 4308527..b7ed80e 100644
--- a/parser.py
+++ b/parser.py
@@ -87,7 +87,9 @@ class Parser(ParserNav):
 	exprStmt       → expression ";" ;
 	printStmt      → "print" expression ";" ;
 
-	expression     → equality ;
+	expression     → equality |
+	                 ternary ;
+	ternary        → equality "?" expression ":" expression ;
 	equality       → comparison ( ( "!=" | "==" ) comparison )* ;
 	comparison     → term ( ( ">" | ">=" | "<" | "<=" ) term )* ;
 	term           → factor ( ( "-" | "+" ) factor )* ;
@@ -97,7 +99,7 @@ class Parser(ParserNav):
 	primary        → NUMBER | STRING | "true" | "false" | "nil"
 	               | "(" expression ")"
 	               | IDENTIFIER ;
-   """
+	"""
 
 	def __init__(self, tokens: list[Token]):
 		self.tokens = tokens
@@ -147,12 +149,29 @@ def printStmt(self):
 
 	def expressionStmt(self):
 		val = self.expression()
-		assert isinstance(val, Expr)
+
+		# if val is None:
+			# val = Expr()
+			# next assert is now guaranteed... lame
+		assert isinstance(val, (Stmt, Expr)), f"{val}. repr: `"+repr(val)+"`"
+
 		self.consume(TokenType.SEMICOLON, "expected a ';' after expressionStmt. where is my  ; !?")
 		return StmtExpr(val)
 
 	def expression(self):
-		return self.equality()
+		"""
+		expression → equality |
+		             ternary ;
+		"""
+		eq = self.equality()
+
+		if self.match(TokenType.QUESTION):
+			left = self.expression()
+			self.consume(TokenType.COLON, "Expected ':' for a ternary expr.")
+			right = self.expression()
+			return Ternary(eq, left, right)
+		else:
+			return eq
 
 	def equality(self):
 		expr = self.comparison()
diff --git a/scanner.py b/scanner.py
index 87bb436..425a490 100644
--- a/scanner.py
+++ b/scanner.py
@@ -35,6 +35,9 @@ class TokenType(Enum):
 	LESS = '<'
 	LESS_EQUAL = '<='
 
+	QUESTION = '?'
+	COLON = ':'
+
 	# // Literals.
 	IDENTIFIER = auto()
 	STRING = auto()
diff --git a/src.lox b/src.lox
index 38e3caf..728edff 100644
--- a/src.lox
+++ b/src.lox
@@ -1,6 +1,8 @@
-// sample, should write a real program.
-() [] [   ] ([]) (])
-"strings"
-123
-123.1233
 var language = "lox";
+var test =
+	1 == 2 ? "help" : "we cool, no help";
+
+
+"strings";
+123;
+123.1233; // sample, should write a real program.
diff --git a/statements.py b/statements.py
index 5b5960a..eb37028 100644
--- a/statements.py
+++ b/statements.py
@@ -30,7 +30,7 @@ def __init__(self):
 
 	def print(self, stmt):
 		# Visitor.start_walk
-		print(stmt.accept(visitor=self))
+		print(f'{stmt.__class__.__name__}({stmt.accept(visitor=self)})')
 
 	def _exprVisit(self, expr):
 		return expr.accept(visitor=self.exprPrinter)