pan><a href="../Tree/index.html#type-re">Tree.re</a> <span class="arrow">&#45;&gt;</span></span> <span>string <span class="arrow">&#45;&gt;</span></span> <a href="../Tree/index.html#type-re">Tree.re</a></span></code></div><div class="spec-doc"><p><code>derivative r a</code></p><ul class="at-tags"><li class="returns"><span class="at-tag">returns</span> <p>the Brzozowski derivative of RE <code>r</code> with respect to symbol <code>a</code></p></li></ul></div></div><div class="odoc-spec"><div class="spec value