feat: add statements

examples/07_math.peb

@@ -1 +1,2 @@
-3 - (4 / 9 + 1) == 12
+print(3 - (4 / 9 + 1) == 12)
+print(40 + (8 - -1) / 3 - 0.5 * 2)

main.py

@@ -1,11 +1,8 @@
-from typing import Any
+from src.ast.stmt import Stmt
-
-from src.ast.expr import Expr, BinaryExpr, UnaryExpr, LiteralExpr, GroupingExpr
-from src.ast.printer import AstPrinter
 from src.interpreter.interpreter import Interpreter
 from src.lexer import Lexer
 from src.parser.parser import Parser
-from src.token import Token, TokenType
+from src.token import Token
 
 
 def main():
@@ -21,29 +18,13 @@ def main():
         source = f.read()
     lexer: Lexer = Lexer()
     tokens: list[Token] = lexer.process(source, path)
-    print(tokens)
+    print(list(filter(lambda t: t.type not in Parser.IGNORE, tokens)))
-
-    printer: AstPrinter = AstPrinter()
-    ast: Expr = BinaryExpr(
-        UnaryExpr(
-            Token(TokenType.MINUS, "-", None, None),
-            LiteralExpr(123)
-        ),
-        Token(TokenType.STAR, "*", None, None),
-        GroupingExpr(LiteralExpr(45.67))
-    )
-    print(printer.print(ast))
 
     parser: Parser = Parser()
-    ast = parser.parse(tokens)
+    program: list[Stmt] = parser.parse(tokens)
 
-    if ast is None:
-        return
-
-    print(printer.print(ast))
     interpreter: Interpreter = Interpreter()
-    result: Any = interpreter.interpret(ast)
+    interpreter.interpret(program)
-    print(f"Result: {result}")
 
 
 if __name__ == '__main__':

src/ast/stmt.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import TypeVar, Generic
+
+from src.ast.expr import Expr
+
+T = TypeVar("T")
+
+
+@dataclass(frozen=True)
+class Stmt(ABC):
+    @abstractmethod
+    def accept(self, visitor: Visitor[T]) -> T:
+        ...
+
+    class Visitor(ABC, Generic[T]):
+        @abstractmethod
+        def visit_expression_stmt(self, stmt: ExpressionStmt) -> T:
+            ...
+
+        @abstractmethod
+        def visit_print_stmt(self, stmt: PrintStmt) -> T:
+            ...
+
+
+@dataclass(frozen=True)
+class ExpressionStmt(Stmt):
+    expression: Expr
+
+    def accept(self, visitor: Stmt.Visitor[T]) -> T:
+        return visitor.visit_expression_stmt(self)
+
+
+@dataclass(frozen=True)
+class PrintStmt(Stmt):
+    expression: Expr
+
+    def accept(self, visitor: Stmt.Visitor[T]) -> T:
+        return visitor.visit_print_stmt(self)

src/interpreter/interpreter.py

@@ -1,21 +1,26 @@
 from typing import Any
 
 from src.ast.expr import LiteralExpr, GroupingExpr, UnaryExpr, BinaryExpr, Expr
+from src.ast.stmt import Stmt, PrintStmt, T, ExpressionStmt
 from src.interpreter.error import PebbleRuntimeError
 from src.pebble import Pebble
 from src.token import TokenType, Token
 
 
-class Interpreter(Expr.Visitor[Any]):
+class Interpreter(Expr.Visitor[Any], Stmt.Visitor[None]):
-    def interpret(self, expr: Expr) -> Any:
+    def interpret(self, statements: list[Stmt]) -> None:
         try:
-            return self.evaluate(expr)
+            for stmt in statements:
+                self.execute(stmt)
         except PebbleRuntimeError as e:
             Pebble.runtime_error(e)
 
     def evaluate(self, expr: Expr) -> Any:
         return expr.accept(self)
 
+    def execute(self, stmt: Stmt) -> None:
+        stmt.accept(self)
+
     def visit_binary_expr(self, expr: BinaryExpr) -> Any:
         left: Any = self.evaluate(expr.left)
         right: Any = self.evaluate(expr.right)
@@ -75,6 +80,13 @@ class Interpreter(Expr.Visitor[Any]):
     def visit_literal_expr(self, expr: LiteralExpr) -> Any:
         return expr.value
 
+    def visit_expression_stmt(self, stmt: ExpressionStmt) -> None:
+        self.evaluate(stmt.expression)
+
+    def visit_print_stmt(self, stmt: PrintStmt) -> None:
+        value: Any = self.evaluate(stmt.expression)
+        print(value)
+
     @staticmethod
     def is_truthy(value: Any) -> bool:
         if value is None or value is False:

src/keyword.py

@@ -14,4 +14,5 @@ KEYWORDS: dict[str, TokenType] = {
     "false": TokenType.FALSE,
     "true": TokenType.TRUE,
     "null": TokenType.NULL,
+    "print": TokenType.PRINT,
 }

src/parser/parser.py

@@ -1,6 +1,5 @@
-from typing import Optional
-
 from src.ast.expr import Expr, BinaryExpr, UnaryExpr, LiteralExpr, GroupingExpr
+from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt
 from src.parser.error import ParsingError
 from src.pebble import Pebble
 from src.token import Token, TokenType
@@ -25,15 +24,15 @@ class Parser:
         Pebble.token_error(token, msg)
         return ParsingError()
 
-    def parse(self, tokens: list[Token]) -> Optional[Expr]:
+    def parse(self, tokens: list[Token]) -> list[Stmt]:
         self.tokens = list(filter(lambda t: t.type not in self.IGNORE, tokens))
         self.current = 0
         self.length = len(self.tokens)
 
-        try:
+        statements: list[Stmt] = []
-            return self.expression()
+        while not self.is_at_end():
-        except ParsingError:
+            statements.append(self.statement())
-            return None
+        return statements
 
     def is_at_end(self) -> bool:
         return self.current >= self.length
@@ -65,6 +64,12 @@ class Parser:
         if not self.match(token_type):
             raise self.error(self.peek(), error_msg)
 
+    def expect_eol(self, error_msg: str):
+        if self.is_at_end():
+            return
+        if not self.match(TokenType.NEWLINE) and not self.match(TokenType.EOF):
+            raise self.error(self.peek(), error_msg)
+
     # Parsing
     def synchronize(self):
         self.advance()
@@ -75,6 +80,23 @@ class Parser:
                 return
             self.advance()
 
+    def statement(self) -> Stmt:
+        if self.match(TokenType.PRINT):
+            return self.print_stmt()
+        return self.expression_stmt()
+
+    def print_stmt(self) -> Stmt:
+        self.consume(TokenType.LEFT_PAREN, "Missing parentheses")
+        value: Expr = self.expression()
+        self.consume(TokenType.RIGHT_PAREN, "Unclosed parenthesis")
+        self.expect_eol("Expected end of line after statement")
+        return PrintStmt(value)
+
+    def expression_stmt(self) -> Stmt:
+        value: Expr = self.expression()
+        self.expect_eol("Expected end of line after expression")
+        return ExpressionStmt(value)
+
     def expression(self) -> Expr:
         return self.equality()