Associativity of fold-expressions : <p><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4191.html" rel="noreferrer"><strong>N4191</strong></a> proposed fold-expressions to C++. The definition there was that</p>

<pre><code>(args + ...)
</code></pre>

<p>is a left-fold (i.e. <code>(((a0 + a1) + a2) + ...)</code>, and that </p>

<pre><code>(... + args) 
</code></pre>

<p>is a right-fold (i.e. <code>(... + (a8 + (a9 + a10)))</code>. However, the revised paper <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4295.html" rel="noreferrer"><strong>N4295</strong></a> reversed the definitions of left and right unary folds.</p>

<p><strong>Question</strong>: what is the rationale? It seems more intuitive (at least when you are used to left-to-right alphabets) to evaluate <code>(args + ...)</code> from left-to-right.</p>
