list corner case

[Tom Humiston]

The syntax (supplemented by the cheatsheet on Gruber's dingus page)  
already gives us the rules. All we're talking about here is what to do  
when a text appears to invoke rules in a contradictory fashion. So I  
think it's a matter of simply sorting out the priority of these rules.

- If you want an unordered list, you start with a hyphen, plus, or  
asterisk.

- If you want an ordered list, you start with a number and a dot. You  
don't get to choose the individual numbers beyond the first (and any  
attempt will be ignored), and (in the current version, at least) even  
the first will, no matter what, be interpreted as 1.

- If you want a list nested within another, you add indentation.

I've noted the above in the order they're presented by Gruber, more or  
less. And I think there's at least an idea that each is more specific  
than the one before, or occurs "in nature" less generally. As with CSS  
rules, I'd give precedence to specificity.

Let's look at the OP's example:

-  foo
2. bar*

Nested? No -- there's no indentation. Ordered? No -- it doesn't start  
with a number. List? Yes; it starts with a hyphen.

* In all examples, I've substituted foo, bar, and baz in place of  
number words to avoid confusion.

Aristotle's first examples:

*  foo
*  bar
1. baz
2. quux
*  qux

-  foo
-  bar
1. baz
1. quux
-  qux

These come out identical to the first example: Nested? No. Ordered? No  
(again, look at the first list item, then compare it with the rule for  
indicating an ordered list). And thirdly, are they lists at all? Yes:  
one list begins with an asterisk, the other a hyphen.

Waylan's example:

-  foo
    2. bar (with four spaces before)

Nested? Yes, it's indented -- which makes 'bar' the beginning of a  
separate list. Is this separate list ordered? Yes. This leaves only  
the outer list, which is clearly unordered.

Yuri's example:

0. foo
-  bar
2. baz

Nested? No. Ordered? Yes -- it begins with a number (clearly to be  
rendered, according to the rule for ordered lists, as 1 followed by 2  
and 3).

Aristotle's second example:

1. foo
1. bar
1. baz

Nested? No -- there's no indentation. Ordered? Yes; there's a number  
(any number) and a dot before the first item. Again, to be rendered,  
according to the rule, as 1, 2, 3.

Albert's example (or examples):

1. Albert
- flowers
- bicycle

2. Lucy
- food
- water
- wine

Nested? No. Ordered? Yes, both of them. Two separate lists? Yes.

In all of the above, I've used Gruber's syntax to create a three-step  
flowchart, but for greater elucidation we could slice it differently:  
First let us ask, is there nesting, and second, is the list ordered or  
unordered? Based on the syntax, the first question needs only to look  
for an indent, and the second needs only to check the first item's  
marker type.

Further, the syntax and its examples state that ANY number (plus a  
dot) before the first item will trigger an ordered list, and that ANY  
number before a subsequent item will serve only to identify it as  
another list item. So -- happily -- the presence of digits and marks  
that don't follow a linear sequence, no matter what they say of the  
intent of the author or user, needn't concern us.

---

All of this is to say that we've been chasing corner cases when we  
don't need to. Corner cases refer to the superset of possible inputs.  
And given the philosophy implied in Gruber's overview, including the  
statement that Markdown's "syntax is very small, corresponding only to  
a very small *subset* of HTML tags" (emphasis mine), I think this  
focus on corner cases, and the attending abhorrence for the ambiguity  
that Markdown's syntax explicity allows, is clearly against Markdown's  
grain.

Bowerbird is right. The syntax says enough about it. Let it go.