Shallow & Deep Binding - What would this program print?

问题

I'm not sure how to do this...

function f1()
{
    var x = 10;
    function f2(fx)
    {
        var x;
        x = 6;
        fx();
    };

    function f3()
    {
        print x;
    };

    f2(f3);
};

For each of the following two binding methods, what would the program print? A) Shallow Binding B) Deep Binding

Thanks for the help!

回答1:

Deep/shallow binding makes sense only when a procedure can be passed as an argument to a function.

• Deep binding binds the environment at the time a procedure is passed as an argument.
• Shallow binding binds the environment at the time a procedure is actually called.

Deep binding.

Here f3() gets the environment of f1() and prints the value of x as 10 which is local variable of f1().

Shallow binding.

f3() is called in f2() and hence gets the environment of f2() and prints the value of x as 6 which is local to f2()

回答2:

• The environment of the call statement that enacts the passed subprogram (shallow binding)

• The environment of the definition of the passed subprogram (deep binding).

In some cases, the subprogram that declares a subprogram also passes that subprogram as a parameter. In those cases, deep binding and ad hoc binding are the same.

回答3:

Shallow binding : the environment of call statement that enacts the passed subprogram Deep binding : the environment of the definition of the passed subprogram Ad hoc binding : the environment of call statement that passed the subproblem as an actual parameter

来源：https://stackoverflow.com/questions/15550648/shallow-deep-binding-what-would-this-program-print