One approach is to make ISO dates lexemes. That way the longest match
discipline works for you, slurping up all the minus signs before the
subtraction logic gets to see them. And whitespace won't be allowed,
which I assume is the intent. I've tried it out in a pull request.
Some of your tests fail, but I am assuming that's because you're working
on that stuff.
-- jeffrey
On 05/20/2014 10:18 AM, Steven Haryanto wrote:
Still playing with Marpa. Recently released a small utility to
calculate dates: https://metacpan.org/pod/App::datecalc
The calculator allows writing date literals in the form of YYYY-MM-DD,
e.g. 2014-05-20. Other allowable literals include date duration in the
form of ISO 8601 notation (e.g. P1Y2M3D) or natural (e.g. "1 year 2
months 3 days").
I'm also trying to add some numeric arithmetics capability to the
calculator, so it can do simple arithmetics on numbers e.g. '2014 -
10' (2004) or '3*2 * P1D' (meaning 6 times the duration of 1 day).
And that's where I'm currently stuck. My latest attempt at the time of
this writing:
https://github.com/sharyanto/perl-App-datecalc/commit/3df0bd0cc681be7bd3a535469ac0fbe439df7deb
If I define op_addsub ~ [+-] then Marpa will treat a date literal
'2014-05-20' as subtraction operation, yielding 1979. If I require
whitespaces around the subtraction operator (i.e. op_addsub ~ [+] | '
- ') then Marpa will refuse to parse '1-2' (no whitespaces around the
minus sign). Moreover, DATE-DATE (subtraction of two dates) doesn't
work anymore.
Pointers are very much appreciated.
Regards,
Steven
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