Re: [TCLCORE] ANN: maybe package for null handling

[Alexandre F. <ale...@gm...>]

On 6/15/08, Fredderic Unpenstein <mag...@gm...> wrote:
>
> How do the [cons] or [list] based methods achieve this?  By using some
> value that they hope no one else will use.  But what to do if some
> piece of script comes along and wants to return a string that just
> happens to look like the string rep of your [cons] and [list] methods.

No, you missed the point.

The Maybe method (be it implemented with Neil's package, with Cons, or
wit hplain 2-element lists) encodes the nullity of a value
out-of-band:

(example with 2-element lists as it is doable in pure Tcl)

     Nothing == {0 whatever}
     Some foobar == {1 foobar}
for any $x
     Some $x ==[list 1 $x]

You can see that no $x this side of the universe will swallow the "1 "
prefix (since you're talking about string reps).

-Alex