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Carl Fredrik Samson
2020-02-06 00:47:11 +01:00
parent b18ba1464c
commit eda2f7dc59
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book/4_pin.html
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@@ -162,22 +162,21 @@
</blockquote>
<p>We already got a brief introduction of <code>Pin</code> in the previous chapters, so we'll
start off without any further introduction.</p>
<p>Let's jump strait to some definitions and then create a set of rules to remember. Let's call them the 10 commandments of Pinning. Unfortunately, my stonemasonry
skills are rather poor, so we'll have to settle by writing them in markdown
(for now).</p>
<p>Let's jump strait to some definitions and then create 10 rules to remember when
we work with <code>Pin</code>.</p>
<h2><a class="header" href="#definitions" id="definitions">Definitions</a></h2>
<p>Pin consists of the <code>Pin</code> type and the <code>Unpin</code> marker. Pin's purpose in life is
to govern the rules that need to apply for types which implement <code>!Unpin</code>.</p>
<p>Pin is only relevant for pointers. A reference to an object is a pointer.</p>
<p>Yep, you're right, that's double negation right there. <code>!Unpin</code> means
&quot;not-un-pin&quot;.</p>
<p>This naming scheme is Rust deliberately testing if you're too tired to safely implement a type with this marker. If you're starting to get confused by
<p><em>This naming scheme is Rust deliberately testing if you're too tired to safely implement a type with this marker. If you're starting to get confused by
<code>!Unpin</code> it's a good sign that it's time to lay down the work and start over
tomorrow with a fresh mind.</p>
tomorrow with a fresh mind.</em></p>
<blockquote>
<p>I hope you didn't mind the joke. There are valid reasons for the names
that were chosen. If you want you can read a bit of the discussion from the
<a href="https://internals.rust-lang.org/t/naming-pin-anchor-move/6864/12">internals thread</a>. The best takeaway from there in my eyes
<p>On a more serious note, I feel obliged to mention that there are valid reasons for the names
that were chosen. If you want to you can read a bit of the discussion from the
<a href="https://internals.rust-lang.org/t/naming-pin-anchor-move/6864/12">internals thread</a>. One of the best takeaways from there in my eyes
is this quote from <code>tmandry</code>:</p>
<p><em>Think of taking a thumbtack out of a cork board so you can tweak how a flyer looks. For Unpin types, this unpinning is directly supported by the type; you can do this implicitly. You can even swap out the object with another before you put the pin back. For other types, you must be much more careful.</em></p>
</blockquote>