Adding a time interval to an interval

On Mon, Jul 22, 2013 at 8:24 PM, Simon Schick simonsimcity@gmail.comwrote:

On Tue, Jul 2, 2013 at 8:21 AM, Simon Schick simonsimcity@gmail.com
wrote:

On Fri, Jun 28, 2013 at 11:20 PM, Derick Rethans derick@php.net
wrote:

Hey Simon,

PS, please don't top-reply as per mailinglist guidelines:
http://us2.php.net/reST/README.MAILINGLIST_RULES

On Fri, Jun 28, 2013 at 7:10 PM, Derick Rethans derick@php.net
wrote:

I'd like to extend the API of php by a method.

Great, let me know if you need any help with the implementation,
or
when you have any questions on how it currently works.

Sorry - I that was easy to missunderstand ;) I thought of providing
the idea. But I would happily also try to implement it by my own -
just to also have contributed to the php-core. If you could give me
a
hint where to start - I feel quite lost in the code right now ...
even
so I read the great tutorials about php-internals provided by
Anthony
Ferrara.

And this may take some time! I've just started with C/C++.

Do you think this is an easy task to start? Depending on knowledge
of
php-internals ;)

It's not that difficult, but not the easiest thing either. Basically,
you have to do the following steps:

1. in ext/date/lib/interval.c add a function that has two arguments of
   the timelib_rel_time* type. It should return a new
   timelib_rel_time* structure that has the two intervals added up
   together. It shouldn't change either of the original
   timelib_rel_time* arguments. Add the function definition to
   ext/date/lib/timelib.h too.

2. You can only add two timelib_rel_time* arguments if neither of
   first_last_day_of, special, have_weekday_relative, and
   have_special_relative are set. You can'd add a "first day of next
   month" to a "+5 days" interval - it only works for simple y:m:d
   h:i:s
   intervals.

3. In ext/date/php_date.c add:

   a. a new ARG_INFO struct after the one for
   arginfo_date_interval_construct,
   b. Add a new method, "add" after
   PHP_ME_MAPPING(createFromDateString,
   date_interval_create_from_date_string,...
   c. Add a new PHP_FUNCTION(date_interval_add) after the function
   PHP_FUNCTION(date_interval_format) that takes two DateInterval
   objects, extract the timelib_rel_time information, call the new
   function that you've added in step 1, and replace the
   timelib_rel_time* that is part of the DateInterval object with
   the
   returned value.
   d. Add a forwards declaration to php_date.h after
   PHP_FUNCTION(date_interval_create_from_date_string);

4. Make sure that the function can be called both as a procedural way
   (date_interval_add) and an object oriented way
   (DateInterval->add()).

5. Write test cases and put them in ext/date/tests.

That's what I can think off right now.

cheers,
Derick

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Hi, Derick

I thought a bit about the changes here and came up with the following
feedback:

If I can't add intervals where either one is relative, I'd also add a
method isRelative() to the class, where the user can check if it's a
relative interval.
But anyways - what happens if the interval is relative and you try to
access one of the public properties? They're all designed for static
intervals (let's say +5days), right?

What, if the user tries to add a relative to a fixed interval? Should
I trigger a E_WARNING, because it's no breaking error, but the value
can't be calculated?

Bye,
Simon

--

Hi,

here is the patch: https://github.com/php/php-src/pull/390

It's basically what Derick suggested. However there is one issue that
needs
to be resolved - interval normalization (timelib_do_rel_normalize). The
problem is that currently there is no way how to get a base timelib_time
from the interval. It means that it's not possible to find out how many
days
use for normalization. For example if interval1 is 20 days and interval2
is
21 days, then the resulted normalized interval will be 1 month and ??
days... :)

There are few solution that come to my mind:

1. no normalization (currently implemented) - this is the easiest
   solution
   but the result from the example will be 0 months and 41 days can give
   interval that has over 31 days...
2. warning if the resulted interval has more than 28 days (February :) )
3. save base timelib_time with the interval when created and then use it
   as
   a base class - it will probably require some sort of copying or ref
   counting
   but it seems like the most logical solution

What do you think?

Jakub

Hi, Jakub

Many thanks for the implementation. I haven't had the time to do it,
but would really have enjoyed it :)

Now, I'll contribute by a comment:
I think, the most valuable result would be the first option.

Reason: I can also create a date-interval for "90 days".

Here's my example:
php > var_dump(DateInterval::createFromDateString("90 days"));
class DateInterval#3 (8) {
public $y =>
int(0)
public $m =>
int(0)
public $d =>
int(90)
public $h =>
int(0)
public $i =>
int(0)
public $s =>
int(0)
public $invert =>
int(0)
public $days =>
int(0)
}

Adding or substracting some interval from this wouldn't be that
different as something like this:

php > var_dump(DateInterval::createFromDateString("90 days and -3
months"));
class DateInterval#3 (8) {
public $y =>
int(0)
public $m =>
int(-3)
public $d =>
int(90)
public $h =>
int(0)
public $i =>
int(0)
public $s =>
int(0)
public $invert =>
int(0)
public $days =>
int(0)
}

I think, we shouldn't care, as long as both intervals are not relative
(like "next monday").

Btw ... wouldn't be that hard to add a "sub()" method to the class,
substracting a DateInterval ;)

Bye
Simon

Hi Simon,

Thanks for the feedback. I have just added the sub method:
https://github.com/bukka/php-src/commit/88824d475cf8e8dd9b4fa4a09cb252f2f441acad

We just need to wait for Derick when he gets time to review it :) Think
that this is for 5.6 so we have got lots of time anyway... :)

Cheers

Jakub