Learning FLOW3

GSoC 2010 – week summary: May 31st – June 6th

After implementing CLDR reader last week, I focused on various classes which would use data from Common Locale Data Repository.

I started with PluralsReader, a class which will be used in messages (labels) translation process. This class basically returns a form-name (a string, one of: zero, one, two, few, many, other) for a pair of locale and number. In some languages form of noun depends on a number expressed in a sentence – for example, unit such as time or currency. English has only two rules (forms “one” and “other”), for example:

form "one": 1 day
form "other": 0 days, 2 days, 5 days, ...

A rule used here is simple, and can be written like this:

<pluralRule count="one">n is 1</pluralRule>

(it is actually how rules are defined in CLDR)

For other languages, rules can be very complicated:

<pluralRules locales="hr ru sr uk be bs sh">
    <pluralRule count="one">n mod 10 is 1 and n mod 100 is not 11</pluralRule>
    <pluralRule count="few">n mod 10 in 2..4 and n mod 100 not in 12..14</pluralRule>
    <pluralRule count="many">n mod 10 is 0 or n mod 10 in 5..9 or n mod 100 in 11..14</pluralRule>
    <!-- rest are plurals -->
</pluralRules>

PluralsReader class can parse these rules and define which form should be used for particular number. I committed this class (among others related) in Revision 4399.

When I wrote plurals reader, I started with another, similar class – NumbersReader. This one is more complicated. It can format a number (float or integer) using a format string. Syntax of format strings (patterns) is defined in CLDR. It’s very flexible and pretty complicated.

I didn’t implement all features described in CLDR (or to be precise: in Unicode Technical Standard #35), although I wanted the NumbersReader to support as much of the syntax as possible. I came across a solution of similar problem in Yii Framework codebase – it was very good starting point for me.

These are examples of formats supported by NumbersReader (one format per line):

#,##0.###
##0%
#,##0.00
00000.0000
'#,##0.0;(#)
¤ #,##0.00;¤ #,##0.00-
#,##0.05

NumbersReader class can parse format – it stores all parsed formats in the cache – and then can format a number using parsed representation of the format. It has methods for formatting decimal / percent / currency numbers (formats are extracted from CLDR). Formatting with custom format is also possible.

NumbersReader was commited in Revision 4445.

Next week I will work on similar Reader class for date and time. Hopefully I will also have time to do something with currency formatting – as for now, NumbersReader can format a value with currency sign, but it is simplified (just replacing currency placeholder with currency sign provided). CLDR has pretty extensive data for currencies.

Tags: gsoc, summary