Eoin Prout

Yes! Regular Expressions are simple once you learn the grammar, and thats also the biggest problem with them, unless you learn the grammar, Regular Expressions look like the gibberish of some dark art, And unless you actually sit down and study you’ll not make much progress with them.

There are some good books on Regular Expressions.
Regular Expression Pocket Reference

Mastering Regular Expressions

Once you have Regular Expressions in your tool box you’ll quickly see many uses they can be put to such as page scraping or data validation, I’ve even seen them used them for updating Delphi code bases to the latest version of Delphi.

In the train timetable service I used 3 Regular expressions to extract the information need to output optimized version of the time table.

The first two

/<input type=”hidden” name=”DepTime” value=”[0-9][0-9]:[0-9][0-9]

/<nput type=”hidden” name=”ArrTime” value=”[0-9][0-9]:[0-9][0-9]

Are used to strip out the table elements which contain the departure and arrival times,
The strings which match the patterns are stored in two arrays, one for arrival and one of departures.

Then iterating through the two arrays a third regular expression is used

[0-9][0-9]:[0-9][0-9]

This Regular Expression returns the times from the strings contained in the two arrays and it is this information which is used to produce the timetables you see when using the service.

I’d be interested to hear an if there is an even easier way to do this.

There is an excellent tool available for working with Regular Expression, Regex Buddy It is a fantastic piece of software.

Most languages and platforms support Regular Expressions, For Delphi you can use the TRegex component which is free, for Delphi .NET it’s not needed as .NET supports Regular Expressions.

In one of my previous posts I moaned about the high cost of the mobile internet in Ireland, The site I used as an example was Irishrail.com, I use this site a lot, checking the Cork/Cobh timetables. I wanted to be able to check the train times on my mobile but I wouldn’t use the Irish Rail website when it costs so much to do so. I decided to create a REST style web service optimized for the mobile internet, i.e. use as little bandwidth as possible.
It’s also be a chance to try out some ideas related to REST.

IMHO REST is the way to construct web services.

The Service is available here and you get your timetable by traversing the links.
OR
You can go directly to the timetable you want by constructing the URL based in the Format
http://www.eoinprout.com/trains/DeparturePoint/Destination
For Example
http://www.eoinprout.com/Cobh/Cork/
http://www.eoinprout.com/Cork/Cobh/

The service will show the timetable for trains between your destination and point of departure for the day, bookmarking the timetable will allow you to quickly check “Todays” timetable.
The service returns “Todays” timetables, If I’m planning journeys far in advance I’ll use my PC, The phone is for when I need to check when the next train home is :). If anyone really wants it changed to support dates in the future just ask.

Of course the first question you ask is, “How much bandwidth does it save ?”
It saves a lot.

It’s not possible to construct the URL for a particular timetable on Irishrail.com because it’s using a POST to send parameters rather then a GET, Interestingly this means that the timetable cannot be bookmarked to allow quick access.

The service was created using PHP and mod_rewrite, which I’ll talk more about in the future as I’m going to be using this service to illustrate REST.

Most new mobile phones have internet capabilities which makes it possible to browse the web while out and about.
The big problem with these services is the high cost of bandwidth on the mobile networks .
The basic price plans range from 1 to 2 cents per KB, This may not seem like a lot but it very quickly adds up.

For example, to check today’s train timetable between Cork and Cobh on Irishrail.com requires approx 167kb of data, this can cost as much as €3.34 depending price plan you have chosen with your mobile operator, Expensive for a train timetable.

3G networks have cheaper data rates then the GPRS ones but are still hugely expensive compared to standard broadband.

You can try reducing the amount of unnecessary data that downloads by turning off images, sounds and animations. But what is really needed are sites with content optimized for the mobile web.
In the old days, as a rule of thumb, we tried to keep a web page to 50kb or less.
We shouldn’t always assume a fast cheap Internet connection is being used.