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The standard library is missing a mutable.TreeMap implementation. #4147

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scabug opened this Issue Jan 10, 2011 · 12 comments

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scabug commented Jan 10, 2011

= problem =
When converting code-bases as a proof of concept it is often necessary to have some working code after a short time. Having no mutable sorted implementations of Map is a big obstacle, because it forces code using it to be rewritten (which might make sense in a later step though) and makes it hard to argue that Scala is a good upgrade path from Java.

= analysis =
immutable.TreeMap exists but mutable implementation is missing in Scala's standard library.

= enhancement recommendation =
Scala should ship with support for this data structure.

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scabug commented Jan 10, 2011

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scabug commented Jan 20, 2011

tim8dev said:
Well, I'm currently working on a mutable TreeSet/Map Implementation based on an AVL Tree.
While it is on average a bit more costly (but still O(log n)) to insert a value into an AVL Tree compared to a Red-Black Tree, it can check containments faster than Red-Black Trees because they are more balanced.

Well.. I've only implemented insert and contains yet, but we'll see what I can do over the weekend.
Some performance results:
n = 1 << 28
Creating Sets through insertion of n randomly generated numbers:
Immutable TreeSet: 14658 ms
My AVL TreeSet: 6129 ms
HashSet (immutable): 13397 ms
Checking containment of n randomly generated numers:
Immutable TreeSet: 6745 ms
My AVL TreeSet: 3948 ms
HashSet (immutable): 1797 ms

So, it's at least not slower :D

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scabug commented Jan 20, 2011

tim8dev said:
Sorry, for double post, but it's just unreadable, w/o line-breaks. [[BR]]
[[BR]]
Well, I'm currently working on a mutable TreeSet/Map? Implementation based on an AVL Tree. While it is on average a bit more costly (but still O(log n)) to insert a value into an AVL Tree compared to a Red-Black Tree, it can check containments faster than Red-Black Trees because they are more balanced.[[BR]]
[[BR]]
Well.. I've only implemented insert and contains yet, but we'll see what I can do over the weekend. Some performance results: n = 1 << 28 Creating Sets through insertion of n randomly generated numbers:[[BR]]
Immutable TreeSet: 14658 ms[[BR]]
My AVL TreeSet: 6129 ms[[BR]]
HashSet (immutable): 13397 ms[[BR]]
Checking containment of n randomly generated numers:[[BR]]
Immutable TreeSet: 6745 ms[[BR]]
My AVL TreeSet: 3948 ms[[BR]]
HashSet (immutable): 1797 ms[[BR]]
[[BR]]
So, it's at least not slower :D[[BR]]

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scabug commented Jan 24, 2011

@lindydonna said:
We agree that it would be good to include these features, but we don't have the resources to create a robust implementation. If someone creates a good implementation with full tests (e.g., tim8dev or someone else), there is a good chance that someone can pick it up and integrate it with the standard library.

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scabug commented Jun 11, 2011

Lucien Pereira (lpereira) said:
I implemented a mutable TreeSet backed by an immutable AVL Tree.
You can find my proposal here : https://github.com/lpereir4/t4147
Assertion based test and scalacheck test can be found in src/test/scala

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scabug commented Jun 19, 2011

Craig P. Motlin (motlin) said:
Is it reasonable to start by porting java.util.TreeMap or would that be a license problem?

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scabug commented Jun 19, 2011

Lucien Pereira (lpereira) said:
I think It would be easier to write it from scratch.

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scabug commented Jan 27, 2012

@soc said:
TreeSet was merged in scala/scala@51ddeb3

Now only mutable.TreeMap is missing.

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scabug commented Feb 21, 2012

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scabug commented Mar 14, 2012

Lucien Pereira (lpereira) said:
Documentation has been updated Simon.

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scabug commented May 10, 2015

@ruippeixotog said:
I may be needing this in one of my projects. If you're still into adding a mutable.TreeMap to the standard Scala collections, I can do a PR to 2.12.x once (and if) I'm able to implement it :) Personally, I think a mutable sorted map is more than common enough to warrant appearing in the standard lib of a programming language.

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scabug commented May 30, 2015

@Ichoran said:
Note that this would also (arguably) resolve #6938

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