feat(repl): evaluate expression statements and print value

src/repl.py

@@ -2,8 +2,9 @@ import atexit
 import readline
 from pathlib import Path
 
-from src.ast.stmt import Stmt
+from src.ast.stmt import Stmt, ExpressionStmt
 from src.completer.completer import Completer
+from src.interpreter.error import PebbleRuntimeError
 from src.interpreter.interpreter import Interpreter
 from src.interpreter.resolver import Resolver
 from src.parser.parser import Parser
@@ -91,6 +92,14 @@ class REPL:
                 continue
 
             try:
+                if len(program) == 1 and isinstance(program[0], ExpressionStmt):
+                    stmt: ExpressionStmt = program[0]  # type: ignore
+                    try:
+                        value = self.interpreter.evaluate(stmt.expression)
+                        print(self.interpreter.stringify(value))
+                    except PebbleRuntimeError as e:
+                        Pebble.runtime_error(e)
+                else:
                     self.interpreter.interpret(program)
             except KeyboardInterrupt:
                 print()