feat(interpreter): add global time function

examples/11_function_call.peb

@@ -0,0 +1,3 @@
+let t = time()
+print("Time is")
+print(t)

src/core/callable.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
-from typing import Any, TYPE_CHECKING
+from typing import Any, TYPE_CHECKING, Callable
 
 if TYPE_CHECKING:
     from src.interpreter.interpreter import Interpreter
@@ -15,3 +15,16 @@ class PebbleCallable(ABC):
     @abstractmethod
     def call(self, interpreter: Interpreter, arguments: list[Any]) -> Any:
         ...
+
+
+def make_builtin(func: Callable[[Interpreter, list[Any]], Any], nargs: int = 0) -> PebbleCallable:
+    class BuiltinFunction(PebbleCallable):
+        def arity(self) -> int:
+            return nargs
+
+        def call(self, interpreter: Interpreter, arguments: list[Any]) -> Any:
+            return func(interpreter, arguments)
+
+        def __str__(self):
+            return f"<native function>"
+    return BuiltinFunction()

src/interpreter/globals.py

@@ -0,0 +1,10 @@
+import time
+
+from src.core.callable import make_builtin
+from src.interpreter.environment import Environment
+
+
+class GlobalEnvironment(Environment):
+    def __init__(self):
+        super().__init__()
+        self.define("time", make_builtin(lambda interpreter, args: time.time()))

src/interpreter/interpreter.py

@@ -1,3 +1,4 @@
+import time
 from typing import Any, Optional
 
 from src.ast.expr import LiteralExpr, GroupingExpr, UnaryExpr, BinaryExpr, Expr, VariableExpr, AssignExpr, LogicalExpr, \
@@ -6,16 +7,19 @@ from src.ast.stmt import Stmt, PrintStmt, ExpressionStmt, LetStmt, BlockStmt, If
 from src.core.callable import PebbleCallable
 from src.interpreter.environment import Environment
 from src.interpreter.error import PebbleRuntimeError
+from src.interpreter.globals import GlobalEnvironment
 from src.pebble import Pebble
 from src.token import TokenType, Token
 
 
 class Interpreter(Expr.Visitor[Any], Stmt.Visitor[None]):
     def __init__(self):
-        self.env: Environment = Environment()
+        self.global_env: GlobalEnvironment = GlobalEnvironment()
+        self.env: Environment = self.global_env
 
     def interpret(self, statements: list[Stmt]) -> None:
-        self.env.clear()
+        self.global_env = GlobalEnvironment()
+        self.env = self.global_env
         try:
             for stmt in statements:
                 self.execute(stmt)