span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span> Error in my_internal_function(x, y) : </span>
<span class="r-out co"><span class="r-pr">#&gt;</span>   Argument 'y' must be numeric but currently isn't.</span>
<span class="r-in"><span><span class="co"># Since the user has no clue of what my_internal_function is,</span></span></span>
<span class="r-in"><span><span class="co">#  s/he will be puzzled of what to do to sort this out</span></span></span>
<span class="r-in"><span></span></