How can functions be evaluted in old environments that aren’t aroud anymore?
- The language implementation keeps them (old environments) around as necessary
We can define the semantics of functions as follows:
- A function value has two parts
- The code part (obviously)
- The environment part that was current when the function was defined
- This is a “pair” like
(func_code, current_env), but you cannot access either piece of this pair. - All you can do is call this “pair”
- This pair is called a
function closure - A call evaluates the code part in the environment (extended with the function argument)