[jira] [Created] (GROOVY-7802) `MapWithDefault` shouldn't store its default value

["Pap Lőrinc (JIRA)" <ji...@apache.org>]

Pap Lőrinc created GROOVY-7802:
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             Summary: `MapWithDefault` shouldn't store its default value
                 Key: GROOVY-7802
                 URL: https://issues.apache.org/jira/browse/GROOVY-7802
             Project: Groovy
          Issue Type: Bug
          Components: groovy-jdk
    Affects Versions: 2.4.6
            Reporter: Pap Lőrinc


As described in https://github.com/apache/groovy/pull/267, a Groovy map with a default value stores all the accessed elements, even if they weren't added explicitly, just queried.

In certain algorithms (e.g. https://github.com/careercup/CtCI-6th-Edition-Groovy/blob/d116d65469bdf17d1e215e89f3e76ac3a97660a9/src/main/groovy/Ch04_TreesAndGraphs/_04_12_PathsWithSum.groovy#L21) the complexity would automatically be reduced, if default values would be deleted (i.e. a default of 0 that is incremented and decremented in a recursive algorithm).

Topics of discussion:
* Currently a `getAt` will `add` also, therefore `containsKey` isn't the same as `getAt(...) != null`
* After the change `keySet()/entrySet()` wouldn't include default values

I proposed alternatives:
* `removeIfDefault(Object)` // removes current key, if value is equal to default
* `consolidate()` // removes all default values
* constructor parameter `STORE_DEFAULT storeDefaultValues = STORE_DEFAULT.FALSE`, or maybe with a `boolean`, though I find primitive parameters confusing

others:
* `containsKey` should always return `true`, or throw an exception, since its behavior is inconsistent

Waiting for your thoughts :)



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