Implicit navigator for maps

[nathanmarz]

Maps could implicitly act as a filter function checking the structure of the value in question, e.g.: {:type "a"} could stay navigated only if the value for the :type key is "a". Likewise, {:k1 {:k2 "b"} :k3 "c"} would check two values, one of them being nested in another map. This is a common use case for which selected? is more verbose than an anonymous function.

This navigator should also work properly with locals in the closure, such as {:type some-local}.

[barrtrek]

I could use this yesterday :)

[nathanmarz]

Closing this because not sure this is a good idea. May reopen in the future if there's a more compelling idea for maps as implicit navs.