From: shugo@... Date: 2019-06-17T08:01:59+00:00 Subject: [ruby-core:93196] [Ruby trunk Feature#15897] `it` as a default block parameter Issue #15897 has been updated by shugo (Shugo Maeda). Eregon (Benoit Daloze) wrote: > shugo (Shugo Maeda) wrote: > > > I think we should never purposefully introduce something ugly in the language. > > > > So let's reject both proposals. > > That's not what I meant. I'd rather not have something ugly in the language at all. > But I think we can make it not ugly, either with `_` or `it` proposed here. `it` doesn't look ugly at first glance, but `it` makes the language semantics dirty as mame admitted in his proposal. > I think readability matters a lot to many people, we typically read code more often than we write. > `_` or `it` seem much better for readability than `@` or `@1`. If `it` is a normal reserved word, I agree with you. However, the semantics of `it` depends on the context, and therefore `@1` is more readable for me. ---------------------------------------- Feature #15897: `it` as a default block parameter https://bugs.ruby-lang.org/issues/15897#change-78641 * Author: mame (Yusuke Endoh) * Status: Open * Priority: Normal * Assignee: matz (Yukihiro Matsumoto) * Target version: ---------------------------------------- How about considering "it" as a keyword for the block parameter only if it is the form of a local varaible reference and if there is no variable named "it"? ``` [1, 2, 3].map { it.to_s } #=> ["1", "2", "3"] ``` If you are familiar with Ruby's parser, this explanation is more useful: NODE_VCALL to "it" is considered as a keyword. Examples: ``` public def it(x = "X") x end [1, 2, 3].map { it.to_s } #=> ["1", "2", "3"] [1, 2, 3].map { self.it } #=> ["X", "X", "X"] # a method call because of a receiver [1, 2, 3].map { it() } #=> ["X", "X", "X"] # a method call because of parentheses [1, 2, 3].map { it "Y" } #=> ["Y", "Y", "Y"] # a method call because of an argument [1, 2, 3].map { it="Y"; it } #=> ["Y", "Y", "Y"] # there is a variable named "it" in this scope it = "Z" [1, 2, 3].map { it.to_s } #=> ["Z", "Z", "Z"] # there is a variable named "it" in this scope ``` Pros: * it is the best word for the feature (according to @matsuda) * it is reasonably compatible; RSpec won't break because their "it" requires an argument Cons: * it actually brings incompatibility in some cases * it is somewhat fragile; "it" may refer a wrong variable * it makes the language semantics dirty Fortunately, it is easy to fix the incompatible programs: just replace `it` with `it()`. (Off topic: it is similar to `super()`.) Just inserting an assignment to a variable "it" may affect another code. This is a bad news, but, IMO, a variable named "it" is not so often used. If this proposal is accepted, I guess people will gradually avoid the variable name "it" (like "p"). The dirtiness is the most serious problem for me. Thus, I don't like my own proposal so much, honestly. But it would be much better than Perlish `@1`. (Note: I don't propose the removal of `@1` in this ticket. It is another topic.) In any way, I'd like to hear your opinions. An experimental patch is attached. The idea is inspired by @jeremyevans0's [proposal of `@`](https://bugs.ruby-lang.org/issues/15723#note-98). P.S. It would be easy to use `_` instead of `it`. I'm unsure which is preferable. ---Files-------------------------------- its.patch (4.92 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: