an class="identifier">ls2</span><span class="special">;</span>
    <span class="identifier">bg</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span><span class="string">"LINESTRING(0 0,1 1,1 2,2 1,2 2)"</span><span class="special">,</span> <span class="identifier">ls1</span><span class="special">);</span>
    <span class="identifier">bg</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span><span class=