Re: [Caml-list] Multi-keyed lookup table?

[Brian Hurt <bhurt@spnz.org>]

On Fri, 8 Aug 2003, Matt Gushee wrote:

> On Thu, Aug 07, 2003 at 03:16:49PM -0500, Brian Hurt wrote:
> > 
> > In the general case, this is hard.  In this specific case, you might 
> > consider just hard coding your levels.  So you'd end up with a data 
> > structure like:
> > 
> >              All font
> >              /   |   \
> >             /    |    \
> >          medium bold light   <-- pick the weight
> >                 / | \
> >               [ ..... ]
> 
> Interesting idea, and not one that I had considered at all. It seems
> quite efficient, too. On the other hand, it looks like the fixed search
> path would make it rather hard to implement fallback rules in case an
> exact match isn't found. It seems to me that that's fairly important for
> fonts: there are many situations where it is preferable to produce some
> output with some fonts not quite right rather than producing nothing.

You certainly can handle * rules by just concatenating results from the 
different children.  You could also do something like:

    match weight with
        "medium" ->
            let t = get_style tree.medium ... in
            match t with
                _ :: _ -> (* we have at least one font *) t
                | [] ->
                    (* try getting something in bold *)
                    let t = get_style tree.bold in
                    ...


Brian


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