The Advent calendar idea ended up terribly. Let us never speak of it again. The holiday season was particularly busy this year with a higher-than-average load of family- friend- and work-related activities. Combine that with an unexpected (and absolutely unappreciated) invasion of a particularly unpleasant and long-lasting stomach bug, and you have something of a perfect storm. I won’t go into the details any further on this particular blog, but I will mention in passing that I’ve become extremely suspicious about the basic hygene habits of the other little turdbags that my son goes to daycare with.

To start 2012 off, and to get back into the swing of coding-for-pleasure, yesterday I went through and got the new Rosella Date library ready for prime time. The library is imperfect and incomplete, but those are things that can be fixed using the patented Andrew Style (tm) of meandering iterative development. For now, however, the library does seem to work well enough for basic tasks and it’s already proven to be a valuable tool for some tasks. Here I’m going to introduce the new library and talk about some of the things I changed in Rosella to support it and some of the ways I’ve already integrated it into the rest of the collection.

String Formatters

When you use sprintf to print out an integer (for instance) you can use some basic modifiers to control how the value is printed. %d prints out the basic version, but you can specify field width, padding, alignment and a few other details by using a format specifier like %-02d. Or, if you want to print the same value out as hex instead of base-10, you can use %x or %X, and use modifiers with those as well.

The problem with something more complex like a date/time representation is that sprintf is not able to handle them natively and some kind of mapping is needed.

Rosella has added a new StringFormatter type to the Core library to help with this problem. A StringFormatter is a type that takes an object and a format string and outputs a new string according to the two. The default StringFormatter uses sprintf internally, but other formatters may use different mechanisms and syntaxes.

var sf = new Rosella.StringFormatter();
string s = sf.format(my_obj, "This is %s");

As an aside, this does demonstrate the fact that our get_string vtable really is insufficient for a lot of purposes. I suggest that get_string should take a parameter for a format string. We could easily incorporate that into the default sprintf implementation like this:

$S0 = sprintf "%{foobar}p", $P0

In that invocation, the get_string vtable on the first parameter would be called with the string argument “foobar”. A normal invocation like this:

$S0 = sprintf "%p", $P0

…would call get_string with a null format and the behavior could be whatever the default string representation for that type is. By overriding get_string in your types to take different formats or to respond to common formats differently, you could have pretty detailed control over stringification at all levels.

Date Library

The new Date library provides a Date type for working with dates and times. You can create one in three ways:

var d = new Rosella.Date(t);
var d = new Rosella.Date(year, month, day);
var d = new Rosella.Date(year, month, day, hour, minute, second);

The first uses a system-specific time integer value to represent a time since the system epoch. This is the kind of value you get from the time opcode, or from stat calls on filesystem objects, for instance. In the third option, hours are specified on a 24-hour clock.

There are also a few functions you can call to get particular dates:

var d =;
var n = Rosella.Date.min();
var x = Rosella.Date.max();

The first value should be the current date/time (as gotten from Parrot’s time opcode). The second value is a minimum date object which corresponds to the minimum possible date value to display and is guaranteed to be evaluated as less than any other date. The third one similarly is a maximum date value which corresponds to the maximum possible date and is guaranteed to always be compared greater than any other date.

Dates are immutable. Once you create them, they cannot be modified in-place. Instead, several operations are provided to perform operations and return new Date objects with the results. Here are some examples:

var d =;
var e = d.add_seconds(20);
e = d.add_hours(15);
e = d.add_months(24);
e = d.add_years(1000);

In each case, the variable e becomes a new date value and d is left unmodified. Two other methods let you pick out just the date components or just the time components:

var n =;
var d =;
var t = n.time();

Finally, you can use a new DateFormatter type to format the date value into a proper stringification:

var d =;
string s = d.format_string("yyyy - MM - dd and the time is: hh:mm:ss");

At the moment the formatter is dirt simple and only supports a few formatting codes such as yyyy, MM, dd, hh, mm, and ss. I will be making it much more useful in the coming days, if I can settle on an algorithm which doesn’t completely stink.


The FileSystem library now returns Date objects from certain file-time methods:

var f = new Rosella.FileSystem.File("t/harness");
var ct = f.change_time();
var at = f.access_time();
var mt = f.modify_time();

In each case, the value returned from the stat call on the file is used to create a new Date object.


Dates are completely comparible, so you can sort them and work with them like other values in an iterable:

var a = [,
    .foreach(function(d) { say(d); });

This toy example sorts the three Date values, with the min first, then now, then max, and prints them out to the console. The stringified versions of the special min/max dates aren’t particularly instructive, but they do get the point across.

So that’s the new Date library. It does need more functionality and definitely needs more tests, but it is working pretty well for me now and has already proven itself useful for a number of purposes. Expect to see more of it in 2012.