As I thought it would be fun to do things a bit differently, I implemented this small exercise using the Pharo platform.

Pharo is a modern Smalltalk implementation that really lets developers enjoy a fully live coding experience.

For the purpose of the exercise, I am fully aware it might be a bit over engineered, but really it was really a good time to develop it, and I hope you'll have a good time reviewing it.

GeoCheck is composed of 3 packages:

• BaselineOfGeoCheck: it is the package that defines the only dependency of the project (PetitParser a parsing engine)
• GeoCheck: the proper code of the app

  • one file per class.

  • one file per extension.

    An extension is a set of methods to be added to classes that already exist in the system --- eg: the method deg in the Number class that return an instance of Angle, so we can write 12 deg and this is an isntance of Angle of 12 degree.

• GeoCheck-Tests: well, you get it, it is all the tests.

First of all you will need the Pharo Virutal Machine, please get the one adapted to your system here:

https://files.pharo.org/get-files/70/.

Then you can download a fully ready image at:

https://github.com/mattonem/GeoCheck/releases/download/v1/geocheckRelease.zip

(64bits --- if you need a 32bits image, you can refer to the next section, or contact me, I would be glad to provide with a 32bits version)

Now you can uncompress the image and the VM, and execute it like so:

/path/toTheVm/pharo --headless /path/toTheImage/geocheckRelease.image geoCheck --file="path/to/customers.txt" --target="53.339428 deg @ -6.257664 deg" --radius="100"

# target/radius options are optional, default will be Dublin with radius 100km 

expected output:

This VM uses a separate heartbeat thread to update its internal clock
and handle events.  For best operation, this thread should run at a
higher priority, however the VM was unable to change the priority.  The
effect is that heavily loaded systems may experience some latency
issues.  If this occurs, please create the appropriate configuration
file in /etc/security/limits.d/ as shown below:

cat <<END | sudo tee /etc/security/limits.d/pharo.conf
*      hard    rtprio  2
*      soft    rtprio  2
END

and report to the pharo mailing list whether this improves behaviour.

You will need to log out and log back in for the limits to take effect.
For more information please see
https://github.com/OpenSmalltalk/opensmalltalk-vm/releases/tag/r3732#linux
======================================
Client ids within 100 km of location -6.257664°  53.339428° are:
12 8 26 6 4 5 11 31 13 15 17 39 24 29 30 23
======================================

NB: because of ressource limitation I was only able to test it in Linux environment. It should work just fine using Windows as it is running on a virtual machine.

In order to load the source code in a brand new image, I would recommend you first install Pharo-launcher.

This app let's handle, all Pharo projects. To start a new project, just double click Pharo7.0-64bits (Stable). Your new project will appear in the right panel. Now run the project (double click). From here we will load the code. First open a playground, to execute some piece of code --- go to Tools -> Playground. In this playground, copy:

Metacello new
   baseline: 'GeoCheck';
   repository: 'github://mattonem/GeoCheck/';
   load.
Smalltalk saveSession

And press the play button on the top right corner. After a couple of second, the image is ready. You can quit and run it via command line. The image should be located in the your USERFOLDER/Pharo/images/<name of the image>/. You can find the vm that pharo-launcher installed in USERFOLDER/Pharo/vm/.

But you can also execute the app from within the GUI and have a taste of what is Pharo --- Follow me the next section.

Let's some fun and execute the application step by step (the best way to assess the architecture of a piece of code).

To do so, clear your playground and execute something like this:

PPGeoCheckParser2Model parse: ('path/to/a/data/file.txt') asFileReference contents.

and press the play button (or do Crtl + G). It will execute the parse on the content of the file and put the result in the right panel.

The result is an array of user nicely parsed. Going the to Raw tab of the result, a text editor will appears at the bottom of the panel. From here you can execute code on the Array instance. So, lets select people close to Dublin by executing:

self select: [ :user | (user geoPosition earthDistanceTo: (53.339428 deg @ -6.257664 deg)) < 100  ] 

Press ctrl + G to execute. A new panel appears displaying only users within 100km from Dublin. If you only want Ids you can execute

self collect: #userId