feat: add break statements

examples/16_break.peb

@@ -0,0 +1,6 @@
+for i to 10 {
+    if i == 5 {
+        break
+    }
+    print(i)
+}

main.py

@@ -4,7 +4,7 @@ from src.pebble import Pebble
 
 
 def main():
-    path: Path = Path("examples/15_resolution.peb")
+    path: Path = Path("examples/16_break.peb")
     Pebble.run_file(path)
 
 

src/ast/stmt.py

@@ -53,6 +53,10 @@ class Stmt(ABC):
         def visit_for_stmt(self, stmt: ForStmt) -> T:
             ...
 
+        @abstractmethod
+        def visit_break_stmt(self, stmt: BreakStmt) -> T:
+            ...
+
 
 @dataclass(frozen=True)
 class BlockStmt(Stmt):
@@ -138,3 +142,11 @@ class ForStmt(Stmt):
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
         return visitor.visit_for_stmt(self)
+
+
+@dataclass(frozen=True)
+class BreakStmt(Stmt):
+    keyword: Token
+
+    def accept(self, visitor: Stmt.Visitor[T]) -> T:
+        return visitor.visit_break_stmt(self)

src/core/function.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-from enum import Enum, auto
 from typing import Any, TYPE_CHECKING
 
 from src.ast.stmt import FunctionStmt
@@ -12,11 +11,6 @@ if TYPE_CHECKING:
     from src.interpreter.interpreter import Interpreter
 
 
-class FunctionType(Enum):
-    NONE = auto()
-    FUNCTION = auto()
-
-
 class PebbleFunction(PebbleCallable):
     def __init__(self, declaration: FunctionStmt, closure: Environment):
         self.declaration: FunctionStmt = declaration

src/formatter.py

@@ -3,7 +3,7 @@ from typing import Any
 from src.ast.expr import Expr, VariableExpr, LiteralExpr, GroupingExpr, UnaryExpr, BinaryExpr, AssignExpr, LogicalExpr, \
     CallExpr
 from src.ast.stmt import Stmt, LetStmt, PrintStmt, IfStmt, ExpressionStmt, BlockStmt, WhileStmt, ForStmt, FunctionStmt, \
-    ReturnStmt
+    ReturnStmt, BreakStmt
 
 
 class Formatter(Expr.Visitor[str], Stmt.Visitor[str]):
@@ -85,10 +85,10 @@ class Formatter(Expr.Visitor[str], Stmt.Visitor[str]):
         return res
 
     def visit_if_stmt(self, stmt: IfStmt) -> str:
-        res: str = self.indented(f"if {self.format(stmt.condition)} {self.format(stmt.then_branch)}")
+        res: str = self.indented(f"if {self.format(stmt.condition)} {self.format(stmt.then_branch).lstrip()}")
         res = res.rstrip("\n")
         if stmt.else_branch is not None:
-            res += f" else {self.format(stmt.else_branch)}"
+            res += f" else {self.format(stmt.else_branch).lstrip()}"
             res = res.rstrip("\n")
         res += "\n"
         return res
@@ -128,3 +128,6 @@ class Formatter(Expr.Visitor[str], Stmt.Visitor[str]):
             res += f" = {stmt.initializer.accept(self)}"
         res += "\n"
         return res
+
+    def visit_break_stmt(self, stmt: BreakStmt) -> str:
+        return self.indented(f"{stmt.keyword.lexeme}\n")

src/interpreter/exceptions.py

@@ -5,3 +5,7 @@ class ReturnException(RuntimeError):
     def __init__(self, value: Any):
         super().__init__()
         self.value: Any = value
+
+
+class BreakException(RuntimeError):
+    pass

src/interpreter/interpreter.py

@@ -4,12 +4,12 @@ from typing import Any, Optional
 from src.ast.expr import LiteralExpr, GroupingExpr, UnaryExpr, BinaryExpr, Expr, VariableExpr, AssignExpr, LogicalExpr, \
     CallExpr
 from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt, LetStmt, BlockStmt, IfStmt, WhileStmt, ForStmt, FunctionStmt, \
-    ReturnStmt
+    ReturnStmt, BreakStmt
 from src.core.callable import PebbleCallable
 from src.core.function import PebbleFunction
 from src.interpreter.environment import Environment
 from src.interpreter.error import PebbleRuntimeError
-from src.interpreter.exceptions import ReturnException
+from src.interpreter.exceptions import ReturnException, BreakException
 from src.interpreter.globals import GlobalEnvironment
 from src.pebble import Pebble
 from src.token import TokenType, Token
@@ -179,7 +179,10 @@ class Interpreter(Expr.Visitor[Any], Stmt.Visitor[None]):
 
     def visit_while_stmt(self, stmt: WhileStmt) -> None:
         while self.is_truthy(self.evaluate(stmt.condition)):
+            try:
                 self.execute(stmt.body)
+            except BreakException:
+                break
 
     def visit_for_stmt(self, stmt: ForStmt) -> None:
         previous_env: Environment = self.env
@@ -224,7 +227,10 @@ class Interpreter(Expr.Visitor[Any], Stmt.Visitor[None]):
 
         while condition():
             self.env.define(stmt.variable.lexeme, value)
+            try:
                 self.execute(stmt.body)
+            except BreakException:
+                break
             value += step_value
 
         self.env = previous_env
@@ -235,6 +241,9 @@ class Interpreter(Expr.Visitor[Any], Stmt.Visitor[None]):
             value = self.evaluate(stmt.initializer)
         self.env.define(stmt.name.lexeme, value)
 
+    def visit_break_stmt(self, stmt: BreakStmt) -> None:
+        raise BreakException()
+
     @staticmethod
     def is_truthy(value: Any) -> bool:
         if value is None or value is False:

src/interpreter/resolver.py

@@ -1,12 +1,12 @@
 from __future__ import annotations
 
+from enum import Enum, auto
 from typing import TYPE_CHECKING
 
 from src.ast.expr import Expr, LogicalExpr, VariableExpr, LiteralExpr, GroupingExpr, CallExpr, UnaryExpr, BinaryExpr, \
     AssignExpr
 from src.ast.stmt import Stmt, ForStmt, WhileStmt, LetStmt, ReturnStmt, PrintStmt, IfStmt, FunctionStmt, \
-    ExpressionStmt, BlockStmt
-from src.core.function import FunctionType
+    ExpressionStmt, BlockStmt, BreakStmt, T
 from src.pebble import Pebble
 from src.token import Token
 
@@ -14,11 +14,23 @@ if TYPE_CHECKING:
     from src.interpreter.interpreter import Interpreter
 
 
+class FunctionType(Enum):
+    NONE = auto()
+    FUNCTION = auto()
+
+
+class LoopType(Enum):
+    NONE = auto()
+    WHILE = auto()
+    FOR = auto()
+
+
 class Resolver(Expr.Visitor[None], Stmt.Visitor[None]):
     def __init__(self, interpreter: Interpreter):
         self.interpreter: Interpreter = interpreter
         self.scopes: list[dict[str, bool]] = []
         self.current_func: FunctionType = FunctionType.NONE
+        self.current_loop: LoopType = LoopType.NONE
 
     def resolve(self, *objects: Expr | Stmt) -> None:
         for obj in objects:
@@ -126,10 +138,15 @@ class Resolver(Expr.Visitor[None], Stmt.Visitor[None]):
         self.define(stmt.name)
 
     def visit_while_stmt(self, stmt: WhileStmt) -> None:
+        enclosing_loop: LoopType = self.current_loop
+        self.current_loop = LoopType.WHILE
         self.resolve(stmt.condition)
         self.resolve(stmt.body)
+        self.current_loop = enclosing_loop
 
     def visit_for_stmt(self, stmt: ForStmt) -> None:
+        enclosing_loop: LoopType = self.current_loop
+        self.current_loop = LoopType.FOR
         self.begin_scope()
         self.declare(stmt.variable)
         self.define(stmt.variable)
@@ -141,3 +158,8 @@ class Resolver(Expr.Visitor[None], Stmt.Visitor[None]):
             self.resolve(stmt.step)
         self.resolve(stmt.body)
         self.end_scope()
+        self.current_loop = enclosing_loop
+
+    def visit_break_stmt(self, stmt: BreakStmt) -> None:
+        if self.current_loop == LoopType.NONE:
+            Pebble.token_error(stmt.keyword, "Cannot break outside a loop")

src/keyword.py

@@ -18,4 +18,5 @@ KEYWORDS: dict[str, TokenType] = {
     "null": TokenType.NULL,
     "print": TokenType.PRINT,
     "return": TokenType.RETURN,
+    "break": TokenType.BREAK,
 }

src/parser/parser.py

@@ -3,7 +3,7 @@ from typing import Optional
 from src.ast.expr import Expr, BinaryExpr, UnaryExpr, LiteralExpr, GroupingExpr, VariableExpr, AssignExpr, LogicalExpr, \
     CallExpr
 from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt, LetStmt, BlockStmt, IfStmt, WhileStmt, ForStmt, FunctionStmt, \
-    ReturnStmt
+    ReturnStmt, BreakStmt
 from src.consts import MAX_FUNCTION_ARGS
 from src.parser.error import ParsingError
 from src.pebble import Pebble
@@ -134,6 +134,8 @@ class Parser:
             return self.print_stmt()
         if self.match(TokenType.RETURN):
             return self.return_stmt()
+        if self.match(TokenType.BREAK):
+            return self.break_stmt()
         if self.match(TokenType.WHILE):
             return self.while_stmt()
         if self.match(TokenType.LEFT_BRACE):
@@ -218,6 +220,11 @@ class Parser:
         self.expect_eol("Expected end of line after return statement.")
         return ReturnStmt(keyword, value)
 
+    def break_stmt(self) -> Stmt:
+        keyword: Token = self.previous()
+        self.expect_eol("Expected end of line after break statement.")
+        return BreakStmt(keyword)
+
     def while_stmt(self) -> Stmt:
         condition: Expr = self.expression()
         body: Stmt = self.statement()

src/token.py

@@ -56,6 +56,7 @@ class TokenType(Enum):
     UNTIL = auto()
     BY = auto()
     RETURN = auto()
+    BREAK = auto()
 
     # Misc
     PRINT = auto()