From: shyouhei@... Date: 2017-02-28T04:08:42+00:00 Subject: [ruby-core:79812] [Ruby trunk Feature#12901] Anonymous functions without scope lookup overhead Issue #12901 has been updated by Shyouhei Urabe. Robert Mosolgo wrote: > What about checking at the block level? I mean, could we check that: > > - All local variable reads come from the block's local table > - There are no method calls on implicit receiver > > So, this could be optimized: > > ~~~ ruby > lambda { |a, b| a + b } > ~~~ Sorry, no. You can look at outside scope from within the lambda's binding like this: ``` zsh % rbenv exec irb irb(main):001:0> a = 1 => 1 irb(main):002:0> b = lambda {|c, d| c + d }.binding => # irb(main):003:0> b.local_variable_set(:a, 2) => 2 irb(main):004:0> a => 2 irb(main):005:0> ``` The lambda does not use variable `a`. But still, you can see through the binding. ---------------------------------------- Feature #12901: Anonymous functions without scope lookup overhead https://bugs.ruby-lang.org/issues/12901#change-63243 * Author: Richard Schneeman * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- 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. -- https://bugs.ruby-lang.org/ Unsubscribe: