<br/><spanstyle="font-weight: bold">Ubuntu</span>: ctrl + shift + U, then 25CA</p><p>The whole command <spanclass="stt">◊define[my-inset]{30%}</span> means “create a variable called <spanclass="stt">my-inset</span> and give it the value <spanclass="stt">30%</span>.”</p><p>Then put the variable into the HTML like so, this time using the ◊ character with the variable name in the two places the value appears:</p><divclass="fileblock"><divclass="SIntrapara"><divclass="fileblock_filetitle"><spanclass="fileblock_filename"><spanclass="stt">"margin.html.pp"</span></span></div></div><divclass="SIntrapara"><divclass="fileblock_filecontent"><divclass="SIntrapara"><blockquoteclass="SCodeFlow"><tablecellspacing="0"cellpadding="0"class="RktBlk"><tr><td><spanclass="RktMeta">#lang</span><spanclass="hspace"> </span><spanclass="RktMeta"></span><ahref="index.html"class="RktModLink"data-pltdoc="x"><spanclass="RktSym">pollen</span></a><spanclass="RktMeta"></span></td></tr><tr><td><spanclass="RktMeta">◊</span><spanclass="RktSym">define</span><spanclass="RktPn">[</span><spanclass="RktSym">my-inset</span><spanclass="RktPn">]</span><spanclass="RktPn">{</span><spanclass="RktMeta">30%</span><spanclass="RktPn">}</span><spanclass="RktMeta"></span></td></tr><tr><td><spanclass="RktMeta"><body</span><spanclass="hspace"> </span><spanclass="RktMeta">style=</span><spanclass="RktVal">"margin:</span><spanclass="hspace"> </span><spanclass="RktVal">◊my-inset;</span><spanclass="hspace"> </span><spanclass="RktVal">border:1px</span><spanclass="hspace"> </span><spanclass="RktVal">solid</span><spanclass="hspace"> </span><spanclass="RktVal">black"</span><spanclass="RktMeta">></span></td></tr><tr><td><spanclass="RktMeta">◊</span><spanclass="RktSym">my-inset</span><spanclass="RktMeta"></span><spanclass="hspace"> </span><spanclass="RktMeta">is</span><spanclass="hspace"> </span><spanclass="RktMeta">the</span><spanclass="hspace"> </span><spanclass="RktMeta">inset.</span></td></tr><tr><td><spanclass="RktMeta"></body></span></td></tr></table></blockquote></div></div></div></div><p>Now reload <ahref="http://localhost:8080/margin.html"><spanclass="stt">margin.html</span></a>. You’ll see that the size of the margin has changed (because of the change to the <spanclass="stt">style</span> attribute) and so has the text of the HTML. If you like, try editing <spanclass="stt">my-inset</span> with different values and reloading the page. You can also try using <spanclass="RktSym">define</span> to create another variable (for instance, to change the color of the box border).</p><p>Still, this is the tiniest tip of the iceberg. The Pollen preprocessor gives you access to everything in the Racket programming language — including math functions, text manipulation, and so on.</p><h4>2.7<tt> </tt><aname="(part._.Markdown_mode)"></a>Markdown mode</h4><p>When used as a preprocessor, Pollen’s rule is that what you write is what you get. But if you’re targeting HTML, who wants to type out all those <spanclass="stt"><tedious>tags</tedious></span>? You can make Pollen do the heavy lifting by using it as a source decoder.</p><p>For instance, Markdown mode. Markdown is a simplified <ahref="https://daringfireball.net/projects/markdown/">notation system</a> for HTML. You can use Pollen’s Markdown decoder by inserting <spanclass="stt">#lang pollen</span> as the first line, and adding the <spanclass="stt">.pmd</span> file extension.</p><p>Try it. In DrRacket, create a file with the following lines and save it as <spanclass="stt">downtown.html.pmd</span>:</p><divclass="fileblock"><divclass="SIntrapara"><divclass="fileblock_filetitle"><spanclass="fileblock_filename"><spanclass="stt">"downtown.html.pmd"</span></span></div></div><divclass="SIntrapara"><divclass="fileblock_filecontent"><divclass="SIntrapara"><blockquoteclass="SCodeFlow"><tablecellspacing="0"cellpadding="0"class
