the next state to test from a given valid
    non-consistent state, see <code class="code">succ</code> for more details.<br>
<pre><span id="VALzero"><span class="keyword">val</span> zero</span> : <code class="type">int -> int <a href="OpamHeuristic.html#TYPEstate">state</a></code></pre><div class="info">
<code class="code">zero n</code> returns the tuple with <code class="code">n</code> zeros, which is the first
    state to explore.<br>
</div>
<pre><span id="VALsucc"><span class="keyword">val</span> succ</