Re: Ada 'hello world' for Android; success!

[Stephen Leake <stephen_leake@stephe-leake.org>]

Georg Bauhaus <rm.dash-bauhaus@futureapps.de> writes:

> On 04.11.11 13:18, Stephen Leake wrote:
>
>> In current OpenToken, we have 'procedure Parse' instead of 'procedure
>> Produce_Subprograms'; the rest is the same. I gather
>> 'Produce_Subprograms' generates Ada code, that must then be compiled.
>
> Yes.
>
>> I'm not clear what the benefit of this is over the current OpenToken
>> approach.
>
> Meant only to be a possible alternative, its implementation is trivial,
> and it automatically reuses mechanisms such as a stack that
> a traditional computer features as a built-in. :-)

It occured to me that one reason to not use the current OpenToken is the
need to run on Ravenscar, with a "no allocations" restriction. But I
think I'd rather use bounded containers in that case; it should not be
too hard to build a generic common interface.

> The given method is exhaustive, if that's needed, it's there.
> If there are no loops in the grammar itself (such as left recursion),
> then the length of input determines the number of recursive
> calls for this method, too, so use of stack space has a known
> maximum.

Ah; I hadn't thought of it that way. That makes this approach ok for
Ravenscar.

> From a programmer's perspective, the method shown will pass tokens
> to handlers. Writers of SAX style content handlers will recognize
> the scheme and find it familiar, I think.

Yes. The equivalent "handlers" in OpenToken are just dispatching
subprograms. 

> Following are some ideas that I would find fairly easy to add
> to the resulting parsers, to make them more useful, more efficient,
> or even more powerful.
> Are they equally easy to add to, for example, bottom up parsers?

I think these are all just moving towards LR parsing; might as well just
go there!

-- 
-- Stephe