From: "cvss (Kirill Vechera)" Date: 2022-01-01T12:30:18+00:00 Subject: [ruby-core:106945] [Ruby master Feature#12901] Anonymous functions without scope lookup overhead Issue #12901 has been updated by cvss (Kirill Vechera). Another reason for having an isolated Proc is using it with an implicit block argument, for example, for `define_method` or for some other metaprogramming. For example, the `yield` on an implicit block argument in this code is incorrect now: ```ruby class A B = proc do yield 'b' end define_method :a, &B end ``` In earlier Ruby versions `yield` produced a runtime error, now it is a parsing error. So `Proc.new(isolate: true){ ... }` approach would require to switch back to the runtime checking ---------------------------------------- Feature #12901: Anonymous functions without scope lookup overhead https://bugs.ruby-lang.org/issues/12901#change-95769 * Author: schneems (Richard Schneeman) * Status: Open * Priority: Normal ---------------------------------------- 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: