Question

Consider the following mark-up input:

* Line 1
* Line 2
:* Line 2.1
:* Line 2.2
* Line 3

This is typically coded as:

  <ul>
    <li>Line 1</li>
    <li>Line 2</li>
    <ul>
      <li>Line 2.1</li>
      <li>Line 2.2</li>
    </ul>
    <li>Line 3</li>
  </ul>

My questions:

• What would be a good representation for the same input using a single line?
• What is the regular expression to generate the corresponding XHTML?

For example, the single line input format could be:

> Line 1 > Line 2 >> Line 2.1 >> Line 2.2 > Line 3

With > being unordered list item delimiter. I chose > because the text might include typical punctuation marks. Using » (or other such non-104-key keys) would be fun, but not as easy to type.

The line input format could also be:

[Line 1][Line 2 [Line 2.1][Line 2.2]][Line 3]

Update #1 – The problem is a little simpler. The number of nests can be limited to three. A general solution for n-levels deep would still be cool.

Update #2 – XHTML, not HTML.

Update #3 – Another possible input format.

Update #4 – Java solutions (or pure regex) are most welcome.

Update #5

Revised code:

String in = " * Line 1 * Line 2 > * Line 2.1 * Line 2.2 < * Line 3";

String sub = "<ul>" + in.replace( " > ", "<ul>" ) + "</ul>";

sub = sub.replace( " < ", "</ul>" );

sub = sub.replaceAll( "( | >)\\* ([^*<>]*)", "<li>$2</li>" );

System.out.println( "Result: " + sub );

Prints the following:

Result: <ul><li>Line 1 </li>* Line 2<ul>* Line 2.1<li>Line 2.2</li></ul>* Line 3

Answer 1

Solution

A working solution follows:

public class Test {
  public Test() {
  }

  public static void main( String[] args ) {
    String in = "= Line 1 = Line 2 > = Line 2.1 = Line 2.2 < = Line 3";

    in = in.replaceAll( "= ([^=<>]*)", "<li>$1</li>" );
    in = in.replace( ">> ", "><ul>" );
    in = in.replace( ">< ", "></ul>" );
    in = "<ul>" + in + "</ul>";
    System.out.println( in );
  }
}

This creates the desired XHTML fragment:

<ul><li>Line 1 </li><li>Line 2 </li><ul><li>Line 2.1 </li><li>Line 2.2 </li></ul><li>Line 3</li></ul>