From: shyouhei@... Date: 2017-03-03T08:40:59+00:00 Subject: [ruby-core:79888] [Ruby trunk Feature#12901] Anonymous functions without scope lookup overhead Issue #12901 has been updated by Shyouhei Urabe. Benoit Daloze wrote: > Shyouhei Urabe wrote: > > This (recomputation) sounds practically very difficult to me, if not impossible. Much easier to avoid optimization at all when binding is used. > > Indeed, I think it's only done for very simple things like arithmetic operations, > where the value can restored from operands and recomputation has no observable side-effect. > > But it's impossible to know if Kernel#binding can be used or not (due to aliasing). True. There are two ways to tackle this problem: 1. add a new construct that does not capture variables outside of a given block. 2. just prohibit obtaining bindings; make lambdas default optimizable. - optionally with something that is statically analyzable to "mark" a lambda to be "volatile", and allow obtaining bindings only within that block. I understand Richard's proposal is #1 while Koichi suggests #2. #2's advantage is that existing codes can benefit. #1 on the other hand won't break existing codes which might be a good property. It seems a matter of allow or disallow binding by default. ---------------------------------------- Feature #12901: Anonymous functions without scope lookup overhead https://bugs.ruby-lang.org/issues/12901#change-63319 * 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: