adding functions `map-vals` and `map-keys`

Description

Many people have been writing a function to map values in HashMap:

Proposal: Add `map-keys` and `map-values` which: maps keys in HashMap, and map values in HashMap. They return HashMap as a result.

Workaround: Using function `reduce-kv` or ordinary `map` and `into` is a common solution, but they are confusing and types change, which makes it tricky and tedious.

Discussions: https://groups.google.com/forum/#!topic/clojure-dev/kkPYIl5qj0o

Environment

None

Assignee

Unassigned

Reporter

hiroyuki fudaba

Labels

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Approval

Vetted

Patch

Code

Priority

Major
Configure