From: eregontp@... Date: 2017-03-02T10:44:24+00:00 Subject: [ruby-core:79868] [Ruby trunk Feature#12901] Anonymous functions without scope lookup overhead Issue #12901 has been updated by Benoit Daloze. To come back to the main topic of this issue, I think having some syntax support for a non-capturing lambda can be a useful feature in Ruby, but should not be for performance reasons. It should be a design tool. If a lambda/proc does not use captured variables, there is no reason for it to lookup parent scopes. So there should not be any scope lookup overhead if a lambda/proc does not capture variables. What is the source of the overhead for calling lambdas on MRI? Is it restoring the implicit state (self, cref, a pointer to the parent frame in case #binding is called, etc) that must be restored? Some extra checks? Kernel#binding applies to all kinds of lambdas/procs and that affects how frames can be represented but it is mostly orthogonal to this issue (methods also have to care about Kernel#binding). ---------------------------------------- Feature #12901: Anonymous functions without scope lookup overhead https://bugs.ruby-lang.org/issues/12901#change-63301 * 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: