function Ruler() {
	  // List of added rules. Each element is:
	  //
	  // {
	  //   name: XXX,
	  //   enabled: Boolean,
	  //   fn: Function(),
	  //   alt: [ name2, name3 ]
	  // }
	  //
	  this.__rules__ = [];

	  // Cached rule chains.
	  //
	  // First level - chain name, '' for default.
	  // Second level - diginal anchor for fast filtering by charcodes.
	  //
	  this.__cache__ = null;
	}
Ruler.after(afterName, ruleName, fn [, options])
- afterName (String): new rule will be added after this one.
- ruleName (String): name of added rule.
- fn (Function): rule function.
- options (Object): rule options (not mandatory).

Add new rule to chain after one with given name. See also
[[Ruler.before]], [[Ruler.push]].

##### Options:

- __alt__ - array with names of "alternate" chains.

##### Example

```javascript
var md = require('markdown-it')();

md.inline.ruler.after('text', 'my_rule', function replace(state) {
  //...
});
```