groovy

DGM push/pop is incompatible with java.util.Deque

Details

  • Type: Bug Bug
  • Status: Open Open
  • Priority: Major Major
  • Resolution: Unresolved
  • Affects Version/s: 1.7.2
  • Fix Version/s: None
  • Component/s: groovy-jdk
  • Labels:
    None
  • Testcase included:
    yes
  • Number of attachments :
    0

Description

The script

Deque stack = new LinkedList()

stack.push(1)
stack.push(2)

assert stack.peek() == 2

fails.

Reason: java.util.LinkedList implements both java.util.List and java.util.Deque. DGM implements push(T) as add(T), and pop() as remove(size() - 1) for java.util.List. However, for Deque push(T) must be equivalent to addFirst(T), and pop() must be equivalent to removeFirst().

Ref.:
http://old.nabble.com/Using-Deque-in-groovy-to28345878.html
http://java.sun.com/javase/6/docs/api/java/util/Deque.html

Activity

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Paul King added a comment -

We should check what other languages (e.g. Ruby) does for non-Deque like lists - flipping both push and pop would have no change visible change to new items pushed and popped - but reverses the order of any initial items. Certainly just defaulting back to the original methods fixes the Deque behavior.

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Paul King added a comment - We should check what other languages (e.g. Ruby) does for non-Deque like lists - flipping both push and pop would have no change visible change to new items pushed and popped - but reverses the order of any initial items. Certainly just defaulting back to the original methods fixes the Deque behavior.
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blackdrag blackdrag added a comment -

during a discussion with Paul I stumbled on the problem, that this is maybe caused bye a wrong handling of DGM methods added to interfaces. A method added to an interface should not shadow an implementation in a class that implements that interface. At least not if the interface implementing class is also implementing the method. LinkedList seems to implement List and a pop/push method, thus the classes method should not be shadowed by a DGM method. Only if we had a LinkedList#pop/push method in DGM, it should be different.

So IMHO this bug is a bug in how DGM methods are applied in the meta class system.

Show
blackdrag blackdrag added a comment - during a discussion with Paul I stumbled on the problem, that this is maybe caused bye a wrong handling of DGM methods added to interfaces. A method added to an interface should not shadow an implementation in a class that implements that interface. At least not if the interface implementing class is also implementing the method. LinkedList seems to implement List and a pop/push method, thus the classes method should not be shadowed by a DGM method. Only if we had a LinkedList#pop/push method in DGM, it should be different. So IMHO this bug is a bug in how DGM methods are applied in the meta class system.

People

  • Assignee:
    Unassigned
    Reporter:
    Alexander Veit
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Dates

  • Created:
    Updated: