Feature #8761: Binding#local_variable_get, set, defined?

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: 2.1.0

[ko1 (Koichi Sasada)]

I propose new 3 methods of Binding.

• Binding#local_variable_get(sym)
• Binding#local_variable_set(sym)
• Binding#local_variable_defined?(sym)

Maybe you can imagine the behavior.

These methods help the following cases:

(1) Access to special keyword arguments

From Ruby 2.0, we can use keyword arguments. And further more, you can use special keyword named such as if', begin' and `end', the language keyword.

However, of course you can't access the local variable `if', because of syntax error.

For example,

def access begin: 0, end: 100
p(begin) #=> syntax error
p(end) #=> syntax error
end

To access such a special keyword parameter, you can use Binding#local_variable_get(sym)

def access begin: 0, end: 100
p(binding.local_variable_get(:begin)) #=> 0
p(binding.local_variable_get(:end)) #=> 100
end

(2) Create a binding with specific local variables

If you wan to make a binding which contains several local variables, you can use Binding#local_variable_set to do it.
(See [Feature #8643])

---

Implementation note:
I think Binding is good place to put these methods than Kernel.
Using binding make it clear that it is need to access to a local environment.
It will help optimization (don't interrupt optimization).

---

You can try these methods on ruby 2.1dev (trunk), committed at r42464.
Your comments are welcome.

This proposal was discussed at dev-meeting at Japan
https://bugs.ruby-lang.org/projects/ruby/wiki/DevelopersMeeting20130727Japan
and Matz accepted it.

[ko1 (Koichi Sasada)]

• Category set to core
• Target version set to 2.1.0

[ko1 (Koichi Sasada)]

• Description updated (diff)

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed

Introduced r42464 and there are no objection.
Close this ticket as accepted feature.