[ruby-core:115593] [Ruby master Bug#20041] Array destructuring and default values in parameters
Issue #20041 has been reported by tenderlovemaking (Aaron Patterson). ---------------------------------------- Bug #20041: Array destructuring and default values in parameters https://bugs.ruby-lang.org/issues/20041 * Author: tenderlovemaking (Aaron Patterson) * Status: Open * Priority: Normal * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- It's possible to set the default value of a parameter to a previous parameter. For example: ```ruby def foo(a, b = a) b end foo([1, 2]) # => [1, 2] ``` However, if the parameters are destructured, the destructring happens _after_ default parameter assignment. For example: ```ruby def foo((x, y), b = x) [x, y, b] end foo([1, 2]) # => [1, 2, nil] ``` Is this expected behavior? I would have expected the parameters to be "evaluated" from left to right, and the array destructuring to happen _before_ the default parameter assignment. Thanks! -- https://bugs.ruby-lang.org/
Issue #20041 has been updated by matz (Yukihiro Matsumoto). It is **not** intended behavior, but under the current implementation, fixing this issue would make the VM far more complex, so we left this behavior untouched, when we found this for the first time. If someone come up with the nice idea, we will reconsider. Matz. ---------------------------------------- Bug #20041: Array destructuring and default values in parameters https://bugs.ruby-lang.org/issues/20041#change-105538 * Author: tenderlovemaking (Aaron Patterson) * Status: Open * Priority: Normal * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- It's possible to set the default value of a parameter to a previous parameter. For example: ```ruby def foo(a, b = a) b end foo([1, 2]) # => [1, 2] ``` However, if the parameters are destructured, the destructring happens _after_ default parameter assignment. For example: ```ruby def foo((x, y), b = x) [x, y, b] end foo([1, 2]) # => [1, 2, nil] ``` Is this expected behavior? I would have expected the parameters to be "evaluated" from left to right, and the array destructuring to happen _before_ the default parameter assignment. Thanks! -- https://bugs.ruby-lang.org/
Issue #20041 has been updated by tenderlovemaking (Aaron Patterson). matz (Yukihiro Matsumoto) wrote in #note-1:
It is **not** intended behavior, but under the current implementation, fixing this issue would make the VM far more complex, so we left this behavior untouched, when we found this for the first time. If someone come up with the nice idea, we will reconsider.
Matz.
Sounds good, thank you. I think I have an idea, but it'll take time for the patch. ---------------------------------------- Bug #20041: Array destructuring and default values in parameters https://bugs.ruby-lang.org/issues/20041#change-105541 * Author: tenderlovemaking (Aaron Patterson) * Status: Open * Priority: Normal * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- It's possible to set the default value of a parameter to a previous parameter. For example: ```ruby def foo(a, b = a) b end foo([1, 2]) # => [1, 2] ``` However, if the parameters are destructured, the destructring happens _after_ default parameter assignment. For example: ```ruby def foo((x, y), b = x) [x, y, b] end foo([1, 2]) # => [1, 2, nil] ``` Is this expected behavior? I would have expected the parameters to be "evaluated" from left to right, and the array destructuring to happen _before_ the default parameter assignment. Thanks! -- https://bugs.ruby-lang.org/
Issue #20041 has been updated by tenderlovemaking (Aaron Patterson). Assignee set to tenderlovemaking (Aaron Patterson) ---------------------------------------- Bug #20041: Array destructuring and default values in parameters https://bugs.ruby-lang.org/issues/20041#change-105543 * Author: tenderlovemaking (Aaron Patterson) * Status: Open * Priority: Normal * Assignee: tenderlovemaking (Aaron Patterson) * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- It's possible to set the default value of a parameter to a previous parameter. For example: ```ruby def foo(a, b = a) b end foo([1, 2]) # => [1, 2] ``` However, if the parameters are destructured, the destructring happens _after_ default parameter assignment. For example: ```ruby def foo((x, y), b = x) [x, y, b] end foo([1, 2]) # => [1, 2, nil] ``` Is this expected behavior? I would have expected the parameters to be "evaluated" from left to right, and the array destructuring to happen _before_ the default parameter assignment. Thanks! -- https://bugs.ruby-lang.org/
participants (2)
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matz (Yukihiro Matsumoto) -
tenderlovemaking (Aaron Patterson)