Does Rust have Collection traits? : <p>I'd like to write a library that's a thin wrapper around some of the functionality in <a href="https://doc.rust-lang.org/std/collections/btree_map/struct.BTreeMap.html">BTreeMap</a>. I'd prefer not to tightly couple it to that particular data structure though. Strictly speaking, I only need a subset of its functionality, something along the lines of the <a href="https://docs.oracle.com/javase/7/docs/api/java/util/NavigableMap.html">NavigableMap</a> interface in Java. I was hoping to find an analogous trait I could use. I seem to recall that at some point there were traits like <code>Map</code> and <code>MutableMap</code> in the standard library, but they seem to be absent now.</p>

<p>Is there a crate that defines these? Or will they eventually be re-added to std?</p>
