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Feature #12901

Anonymous functions without scope lookup overhead

Added by schneems (Richard Schneeman) about 4 years ago. Updated 5 months ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:77921]

Description

Right now if you are writing performance sensitive code you can get a performance bump by not using anonymous functions (procs, lambdas, blocks) due to the scope lookup overhead.

https://twitter.com/apotonick/status/791167782532493312?lang=en

I would like to be able to create an anonymous function and specify I don't need it to perform the lookup when called.

I am thinking that this code:

Proc.new(scope: false) {|var| puts var }

Would be the equivalent of

def anon(var)
  puts var
end

If you call it while trying to access something from outside of the scope it would error

var = "hello"
Proc.new(scope: false) { puts var }.call
# => NameError: undefined local variable or method `var' for main:Object

An example of a case where this could be used is found in https://github.com/rails/sprockets/pull/417. In this case we are getting rid of anonymous functions in favor of a method created with refinements. This solution works but it was not an obvious optimization. It would be convenient to have a syntax for defining anonymous functions that do not need access to caller scope.

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