Add exercise: phone-number

[Teo-ShaoWei]

This is a call-to-arm to issue #87. First time here, pardon me if anything is out of spec. Feel free to inform me on how I can polish it and I will get it fixed.

Some design decisions...

• The main machinery of this question is regex. Instead of mixing up regex with language specifics like some other language tracks, I decided to put the full power on regex. Instead the example demonstrates how Julia can call regex, and create regex using interpolation to improve code readability.
• I did not put in type declaration for the input variable, pending discussion on issue Consider consistency for the exercises #2. I will adhere to the convention of this repo after we concluded the discussion.

[SaschaMann]

This looks good to me. That said, I don't know anything about regex, so I can't say much about the example solution :D

I would leave this as a floating non-core exercise. Understanding regex is not really important in many applications of Julia, so I don't think it should be part of the main progression line in exercism v2. Unless you have another suggestion.

[SaschaMann]

You could use regex string literals here, might look a bit neater.

[Teo-ShaoWei]

Yes I would have preferred to demonstrate regex string literals but I think it is not possible to do regex interpolation (refer to this issue). At the end of it the suggested solution is to use the Regex constructor (as per this discourse). The string looks more unwieldy without interpolation, so I took the lesser of the two evils.

Another way is to extract all the digits first and then check only the digits, but there will be a lot of false positives.

I am not good with regex myself too actually haha... I think the test cases are ok, so we can consider publish it first, and then we might have a submission that solve this nicely =)

[SaschaMann]

Ah okay, I didn't know of that issue.

[Teo-ShaoWei]

Thanks for the review @SaschaMann =)

Yupz I agree with you that this would be a floating non-core exercise. I think I left the config.json entry of this problem as "core": false,. Is that the correct setting?

Exercism v2? That's new to me. Where can I find out more about it?

[SaschaMann]

Yep, that's the correct setting.

Info about exercism v2 is spread out over the discussion and docs repos. One of the major changes is the progression tree as opposed to the current, linear progression.

Some info:
exercism/discussions#175
exercism/discussions#159
exercism/discussions#154

The prototype/beta is available here: v2.exercism.io (Julia isn't deployed on that yet)

[SaschaMann]

Thanks for adding this! :)

[Teo-ShaoWei]

Ah I will give Exercism v2 info a good read. It will be good if we can prepare for it while we import questions.

Thanks for reviewing too. I look forward to working with you and the rest of the team on other imports =)