an><span class="co"># `x` must have length 1</span></span></span>
<span class="r-in"><span><span class="va">x</span> <span class="op">&lt;-</span> <span class="fl">1</span><span class="op">:</span><span class="fl">2</span></span></span>
<span class="r-in"><span><span class="fu">check_positive</span><span class="op">(</span><span class="va">x</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="co"># `x` must not be `NA`</span></span></sp