From: alex@... Date: 2014-03-13T12:20:19+00:00 Subject: [ruby-core:61459] [ruby-trunk - Bug #9605] Chaining "each_with_index.detect &lambda" raises ArgumentError Issue #9605 has been updated by Alex Rothenberg. Wow this gets weirder and weirder. It seems to be happening when jruby turns a lambda created with "->" syntax into a block. MRI does consistently raise ArgumentError in all 4 cases. $ jruby -v -e 'def test(l); l.call(1); end; test(lambda{p :ng})' jruby 1.7.10 (1.9.3p392) 2014-01-09 c4ecd6b on Java HotSpot(TM) 64-Bit Server VM 1.7.0_51-b13 [darwin-x86_64] ArgumentError: wrong number of arguments (1 for 0) call at org/jruby/RubyProc.java:267 test at -e:1 (root) at -e:1 $ jruby -v -e 'def test(l); l.call(1); end; test(->(){p :ng})' jruby 1.7.10 (1.9.3p392) 2014-01-09 c4ecd6b on Java HotSpot(TM) 64-Bit Server VM 1.7.0_51-b13 [darwin-x86_64] ArgumentError: wrong number of arguments (1 for 0) call at org/jruby/RubyProc.java:267 test at -e:1 (root) at -e:1 $ jruby -v -e 'def test; yield 1; end; test(&->(){p :ng})' jruby 1.7.10 (1.9.3p392) 2014-01-09 c4ecd6b on Java HotSpot(TM) 64-Bit Server VM 1.7.0_51-b13 [darwin-x86_64] ArgumentError: wrong number of arguments (1 for 0) test at -e:1 (root) at -e:1 $ jruby -v -e 'def test; yield 1; end; test(&lambda{p :ng})' jruby 1.7.10 (1.9.3p392) 2014-01-09 c4ecd6b on Java HotSpot(TM) 64-Bit Server VM 1.7.0_51-b13 [darwin-x86_64] :ng This feels like its probably a jruby bug and is probably a discussion I should move onto their issue list. ---------------------------------------- Bug #9605: Chaining "each_with_index.detect &lambda" raises ArgumentError https://bugs.ruby-lang.org/issues/9605#change-45754 * Author: Alex Rothenberg * Status: Rejected * Priority: Normal * Assignee: * Category: * Target version: * ruby -v: 2.1.1 * Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN ---------------------------------------- I found an odd edge case where "detect" and "select" behave differently from other methods of Enumerable. Normally these methods yield a single argument to a block but when you chain them after "each_with_index" they yield two arguments "item" and "index". The problem is when you try passing a lambda instead of a block then they raise an ArgumentError $ irb 2.1.1 :001 > lambda = ->(word, index) { word.length == 3 } => # 2.1.1 :002 > %w(Hi there how are you).each_with_index.detect &lambda ArgumentError: wrong number of arguments (1 for 2) from (irb):1:in `block in irb_binding' from (irb):2:in `each' from (irb):2:in `each_with_index' from (irb):2:in `each' from (irb):2:in `detect' from (irb):2 from /Users/alex/.rvm/rubies/ruby-2.1.1/bin/irb:11:in `
' 2.1.1 :003 > %w(Hi there how are you).each_with_index.select &lambda ArgumentError: wrong number of arguments (1 for 2) from (irb):1:in `block in irb_binding' from (irb):3:in `each' from (irb):3:in `each_with_index' from (irb):3:in `each' from (irb):3:in `select' from (irb):3 from /Users/alex/.rvm/rubies/ruby-2.1.1/bin/irb:11:in `
' Interestingly it works just find when calling other methods like "map" 2.1.1 :004 > %w(Hi there how are you).each_with_index.map &lambda => [false, false, true, true, true] It also works when you use a proc 2.1.1 :001 > proc = Proc.new {|word, index| word.length == 3 } => # 2.1.1 :002 > %w(Hi there how are you).each_with_index.detect &proc => ["how", 2] 2.1.1 :003 > %w(Hi there how are you).each_with_index.map &proc => [false, false, true, true, true] or a block 2.1.1 :001 > %w(Hi there how are you).each_with_index.detect {|word, index| word.length == 3 } => ["how", 2] 2.1.1 :002 > %w(Hi there how are you).each_with_index.map {|word, index| word.length == 3 } => [false, false, true, true, true] When testing against JRuby or Rubinius none of these scenarios raise an ArgumentError. I'm guessing this is a bug and not intended behavior. If it is intended then both those implementations have a bug in not raising ArgumentError. -- http://bugs.ruby-lang.org/