HTML Macros

Another feature of FOO is that it allows you to define HTML “macros” that can translate arbitrary forms into HTML s-expressions that the html macro understands. For instance, suppose you frequently find yourself writing pages of this form:

  1. (:html
  2.   (:head (:title "Some title"))
  3.   (:body
  4.     (:h1 "Some title")
  5.     ... stuff ...))

You could define an HTML macro to capture that pattern like this:

  1. (define-html-macro :standard-page ((&key title) &body body)
  2.   `(:html
  3.      (:head (:title ,title))
  4.      (:body
  5.       (:h1 ,title)
  6.       ,@body)))

Now you can use the “tag” :standard-page in your s-expression HTML, and it’ll be expanded before being interpreted or compiled. For instance, the following:

  1. (html (:standard-page (:title "Hello") (:p "Hello, world.")))

generates the following HTML:

  1. <html>
  2.   <head>
  3.     <title>Hello</title>
  4.   </head>
  5.   <body>
  6.     <h1>Hello</h1>
  7.     <p>Hello, world.</p>
  8.   </body>
  9. </html>