I don't think standard Markdown as specified by John Gruber can handle that. You can't use (a,b,c). It has to be arabic numerals.
Markdown will ignore the actual value of the digits. (1,2,3) or (1,1,1) will both be rendered as (1,2,3). This is a result of the way that HTML & CSS deal with lists. The HTML has no way to specify the value to a list item. However, you can use CSS to specify the way each list nesting level is styled. So you can have a list that has Roman Numeral -> Uppercase Letter -> Arabic Numeral -> lowercase letter
Some enhanced version of Markdown may get you closer to what you want. I use MultiMarkdown and check it, but it doesn't support directly using (a,b,c) notation either.
> The HTML has no way to specify the value to a list item.
The "value" attribute of the HTML "li" element does exactly this, but setting the value isn't really what you need for what GP was asking for; setting the kind of marker is. This can, as you note, be done through CSS, but it can also be done through HTML (using the "type" attribute of the "ol" element.)
In the context of conversion of legal documents, where the marker type is intended for reference, it would be semantically correct to do this in HTML, so it would probably be desirable for markdown to support all the marker types supported by HTML for ordered list as markers for ordered lists, and set the type attribute correctly.
So, using a number should result in the current behavior, using a lowercase letter (other than one which might be a lowercase roman numeral, like "i"!) should result in lowercase-alpha markers, etc.
Markdown will ignore the actual value of the digits. (1,2,3) or (1,1,1) will both be rendered as (1,2,3). This is a result of the way that HTML & CSS deal with lists. The HTML has no way to specify the value to a list item. However, you can use CSS to specify the way each list nesting level is styled. So you can have a list that has Roman Numeral -> Uppercase Letter -> Arabic Numeral -> lowercase letter
Some enhanced version of Markdown may get you closer to what you want. I use MultiMarkdown and check it, but it doesn't support directly using (a,b,c) notation either.