feat: add while loops

examples/10_while.peb

@@ -0,0 +1,13 @@
+let i = 0
+let a = 1
+let b = 1
+
+print("Fibonacci")
+
+while i < 10 {
+    print(a)
+    let c = a + b
+    a = b
+    b = c
+    i += 1
+}

main.py

@@ -13,7 +13,7 @@ def main():
     123
     "This is
      another string" """
-    path: str = "examples/09_logical.peb"
+    path: str = "examples/10_while.peb"
     with open(path, "r") as f:
         source = f.read()
     lexer: Lexer = Lexer()

src/ast/stmt.py

@@ -37,6 +37,10 @@ class Stmt(ABC):
         def visit_let_stmt(self, stmt: LetStmt) -> T:
             ...
 
+        @abstractmethod
+        def visit_while_stmt(self, stmt: WhileStmt) -> T:
+            ...
+
 
 @dataclass(frozen=True)
 class BlockStmt(Stmt):
@@ -79,3 +83,13 @@ class LetStmt(Stmt):
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
         return visitor.visit_let_stmt(self)
+
+
+
+@dataclass(frozen=True)
+class WhileStmt(Stmt):
+    condition: Expr
+    body: Stmt
+
+    def accept(self, visitor: Stmt.Visitor[T]) -> T:
+        return visitor.visit_while_stmt(self)

src/interpreter/interpreter.py

@@ -1,7 +1,7 @@
 from typing import Any
 
 from src.ast.expr import LiteralExpr, GroupingExpr, UnaryExpr, BinaryExpr, Expr, VariableExpr, AssignExpr, LogicalExpr
-from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt, LetStmt, BlockStmt, IfStmt
+from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt, LetStmt, BlockStmt, IfStmt, WhileStmt
 from src.interpreter.environment import Environment
 from src.interpreter.error import PebbleRuntimeError
 from src.pebble import Pebble
@@ -133,6 +133,10 @@ class Interpreter(Expr.Visitor[Any], Stmt.Visitor[None]):
         value: Any = self.evaluate(stmt.expression)
         print(value)
 
+    def visit_while_stmt(self, stmt: WhileStmt) -> None:
+        while self.is_truthy(self.evaluate(stmt.condition)):
+            self.execute(stmt.body)
+
     def visit_let_stmt(self, stmt: LetStmt) -> None:
         value: Any = None
         if stmt.initializer is not None:

src/parser/parser.py

@@ -1,7 +1,7 @@
 from typing import Optional
 
 from src.ast.expr import Expr, BinaryExpr, UnaryExpr, LiteralExpr, GroupingExpr, VariableExpr, AssignExpr, LogicalExpr
-from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt, LetStmt, BlockStmt, IfStmt
+from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt, LetStmt, BlockStmt, IfStmt, WhileStmt
 from src.parser.error import ParsingError
 from src.pebble import Pebble
 from src.token import Token, TokenType
@@ -111,6 +111,8 @@ class Parser:
             return self.if_stmt()
         if self.match(TokenType.PRINT):
             return self.print_stmt()
+        if self.match(TokenType.WHILE):
+            return self.while_stmt()
         if self.match(TokenType.LEFT_BRACE):
             return self.block_stmt()
         return self.expression_stmt()
@@ -130,6 +132,11 @@ class Parser:
         self.expect_eol("Expected end of line after statement")
         return PrintStmt(value)
 
+    def while_stmt(self) -> Stmt:
+        condition: Expr = self.expression()
+        body: Stmt = self.statement()
+        return WhileStmt(condition, body)
+
     def block_stmt(self) -> Stmt:
         statements: list[Stmt] = []
         self.skip_newlines()