Issue #20858 has been updated by mame (Yusuke Endoh). Currently, `a, b = c, d = 3, 4` is interpreted as `a, b = c, (d = 3, 4)`. Whether it is good or not. ---------------------------------------- Bug #20858: multiple parallel assignments are inconsistent https://bugs.ruby-lang.org/issues/20858#change-110320 * Author: daveola (David Stellar) * Status: Open * ruby -v: ruby 3.3.5 (2024-09-03 revision ef084cc8f4) [x86_64-linux] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I may have terminology wrong, so apologies. For this bug I'm going to use "multiple assignment" to refer to using multiple assignment operators in a line, such as: ``` ruby a = b = c = 1 ``` And then parallel assignment to refer to doing multiple assignments at the same time using tuples, such as: ``` ruby a,b = 1, 2 ``` Unfortunately combining these is inconsistent. First of all, just doing this: ``` ruby a,b = c,d = 3,4 ``` Gives us: **"undefined local variable or method `c' for main (NameError)"** So if we work around that by defining all our variables, we then get unexpected results: ``` ruby a = b = c = d = 'foobar' a,b = c,d = 3,4 puts "Got: a=#{a} b=#{b} and c=#{c} d=#{d}" # Got: a=foobar b=3 and c=foobar d=3 c,d = 3,4 a,b = c,d puts "Got: a=#{a} b=#{b} and c=#{c} d=#{d}" # Got: a=3 b=4 and c=3 d=4 ``` I can imagine that if multiple parallel assignment is not supported that a,b will not get set properly, but it does not follow that c would be undefined by the expression. -- https://bugs.ruby-lang.org/

Issue #20858 has been updated by matz (Yukihiro Matsumoto). Status changed from Open to Rejected The `a,b = c,(d=3,4)` is the natural combination of the current rules. Changing this could make syntax even more complex. I don't want to change the syntax here. Matz. ---------------------------------------- Bug #20858: multiple parallel assignments are inconsistent https://bugs.ruby-lang.org/issues/20858#change-110954 * Author: daveola (David Stellar) * Status: Rejected * ruby -v: ruby 3.3.5 (2024-09-03 revision ef084cc8f4) [x86_64-linux] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I may have terminology wrong, so apologies. For this bug I'm going to use "multiple assignment" to refer to using multiple assignment operators in a line, such as: ``` ruby a = b = c = 1 ``` And then parallel assignment to refer to doing multiple assignments at the same time using tuples, such as: ``` ruby a,b = 1, 2 ``` Unfortunately combining these is inconsistent. First of all, just doing this: ``` ruby a,b = c,d = 3,4 ``` Gives us: **"undefined local variable or method `c' for main (NameError)"** So if we work around that by defining all our variables, we then get unexpected results: ``` ruby a = b = c = d = 'foobar' a,b = c,d = 3,4 puts "Got: a=#{a} b=#{b} and c=#{c} d=#{d}" # Got: a=foobar b=3 and c=foobar d=3 c,d = 3,4 a,b = c,d puts "Got: a=#{a} b=#{b} and c=#{c} d=#{d}" # Got: a=3 b=4 and c=3 d=4 ``` I can imagine that if multiple parallel assignment is not supported that a,b will not get set properly, but it does not follow that c would be undefined by the expression. -- https://bugs.ruby-lang.org/