     <code class="constant">GL_NOOP</code>,
                    <code class="constant">GL_INVERT</code>,
                    <code class="constant">GL_AND</code>,
                    <code class="constant">GL_NAND</code>,
                    <code class="constant">GL_OR</code>,
                    <code class="constant">GL_NOR</code>,
                    <code class="constant">GL_XOR</code>,
                    <code class="constant">GL_EQUIV</code>,
                    <code class="constant">GL_AND_REVERSE