Simple toy html writer in ruby

gistfile1.rb

# Simple toy html writer in ruby 

def tag(name, *args)
  a = args.length > 0 ? " " + args.join(" ") : ""
  a = "" if a == " "
  name = "p" if name == "§"
  block_given? ? "<#{name}#{a}>" + yield + "</#{name}>\n" : "<#{name}#{a} />"
end

def defmacro(name)
  eval "def #{name}(*args)\n" + yield + "\nend"
end

TAGS = %w[body b strong i em br hr img head title h1 h2 h3 h4 h5 h6 § div input]

TAGS.each { |t|
  defmacro(t) { "block_given? ? tag(\"#{t}\", args) { yield } : tag(\"#{t}\", args)" }
}
# html macro prints its block
defmacro(:html) { "print tag(:html) { yield }" }

# Example

html {
  head {
    title { "Welcome page" }
  } +
  body {
    h1   { "Welcome!" } +
    §  { "This is a test page of " + b { "HTML" } + " generated by Ruby." + br +
         "Nice, isn't " + em { "it" } + "?" } +
    input("type=submit", "name=ok", "value=OK") +
    §  { "This is it" }
  }
}