From: "alexeymuranov (Alexey Muranov)" Date: 2012-08-15T06:50:58+09:00 Subject: [ruby-core:47195] [ruby-trunk - Feature #6869][Open] Do not treat `_` parameter exceptionally Issue #6869 has been reported by alexeymuranov (Alexey Muranov). ---------------------------------------- Feature #6869: Do not treat `_` parameter exceptionally https://bugs.ruby-lang.org/issues/6869 Author: alexeymuranov (Alexey Muranov) Status: Open Priority: Normal Assignee: Category: Target version: 3.0 =begin I started by commenting on #6693, but i have realized that this is a slightly different request. I propose to not treat the variable name "(({_}))" exceptionally. Current behavior: {0=>1}.each_with_index { |_,_| p _ } # [0, 1] prints "[0, 1]", but {1=>2}.each_with_index { |x,x| p x } # SyntaxError: (eval):2: duplicated argument name raises "SyntaxError: (eval):2: duplicated argument name". Similarly for methods: def f(_, _) _ end f(0, 1) # => 0 def f(x, x) x end # => SyntaxError: (eval):2: duplicated argument name Observe also that the use of repeated (({_})) parameter is not consistent between methods and blocks: for methods the value is the first assigned value, and for blocks it is the array of all the assigned values. 1. I propose to use the same rule for all variables, without distinguishing (({_})) specially. In particular i propose to allow to repeat any variable, not only (({_})), in block or method arguments without raising an error. There may be several solutions what the repeated argument will hold: it may hold the array of all assigned values, the first assigned value, the last assigned value, the first non-nil assigned value, or the last non-nil assigned value. 2. I propose to treat repeated arguments in methods and in blocks the same way (do not know which one). 3. For unused variables i propose to introduce a special placeholder, for example "(({-}))" not followed by anything other than a delimiter (comma or bracket): each_with_index { |-, value| puts value } -, -, suffix = parse(name) =end -- http://bugs.ruby-lang.org/