How do I replace specific characters idiomatically in Rust?
<p>So I have the string "Hello World!" and want to replace the "!" with "?" so that the new string is "Hello World?"</p>

<p>In Ruby we can do this easily with the <code>gsub</code> method:</p>

<pre class="lang-rb prettyprint-override"><code>"Hello World!".gsub("!", "?")
</code></pre>

<p>How to do this idiomatically in Rust?</p>