From: eregontp@... Date: 2019-09-24T13:23:08+00:00 Subject: [ruby-core:95057] [Ruby master Bug#16178] Numbered parameters: _1 should be the same as |x| and _0 should not exist Issue #16178 has been updated by Eregon (Benoit Daloze). Of course, having `_` as the only unnamed parameter would have `|x|` semantics, but I guess it's too late for that and now we have `_` parameters. ---------------------------------------- Bug #16178: Numbered parameters: _1 should be the same as |x| and _0 should not exist https://bugs.ruby-lang.org/issues/16178#change-81689 * Author: Eregon (Benoit Daloze) * Status: Open * Priority: Normal * Assignee: Eregon (Benoit Daloze) * Target version: * ruby -v: ruby 2.7.0dev (2019-09-24T12:57:54Z master 0e84eecc17) [x86_64-linux] * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN ---------------------------------------- Currently on trunk: ```ruby array = ["string", 42, [1, 2]] array.map { |x| x * 2 } # => ["stringstring", 84, [1, 2, 1, 2]] array.map { _1 * 2 } # => ["stringstring", 84, 2] ``` Oops, this trivial code just lost data and completely ignored the element class! This is clearly contrary to intuition and is very dangerous. Using `_0` instead has the correct behavior but it's clear we use 1-based indexing for numbered parameters, and it doesn't solve that `_1` has dangerous behavior. Basically the current behavior is that `_0` is the same as `|x|` and `_1` is the same as `|x,|`. `|x,|` is almost never used in Ruby, and for good reasons, it just throws away data/information/the class of the object. Such a dangerous operation should only be done when it's explicit, and the trailing comma in `|x,|` shows that, but `_1` does not. So let's make `_1` be `|x|` and remove `_0`. I am going to be harsh, but this discussion has gone too long without any serious written argument for the current behavior: I believe it's irrational and irresponsible to have `_1` be `|x,|`, it's just going to lead to nasty bugs. Try to convince me otherwise. If not, in one week I want to apply this change. From the discussion in https://bugs.ruby-lang.org/issues/15723#note-127 and in https://bugs.ruby-lang.org/issues/15708 -- https://bugs.ruby-lang.org/ Unsubscribe: