So, on my birthday this year I was expecting a lot of wishes on facebook. I mean who doesnt right? And I wanted to automate the replies instead of going through them manually. So I started looking up the facebook graph api and fql, both of which, now that I have had a brief interaction with, totally rock!
It was easy right. I only needed to go through two steps:
- GET all the posts on my wall between 00:00 hours to 23:59 hours on 1st February 2014.
- Scan through each of them, if it was a birthday wish, POST a generous thank you.
My friends, some of them, aren’t really used to forming complete words, leave apart sentences. So the challenge was not just to form a regular expression for “Happy Birthday” but also for all possible short forms of Happy Birthday. Ones like these:
- Hpy Bday!
- Hhhhppppyyyyy Bddaeee…
This list could be anything that sounds marginally close to a birthday wish. Oh and not to forget, a couple of variants like:
- Many many happy returns of the day.
- Best wishes.
Hell! I even got a HBD in one of the posts! Intensifies my reason to hate sms language even more. But then, thats what programmers should do right? Fix the problems (read bugs) at hand right?
And with a comprehensive data set at my disposal, I set off.
So I broke down the problem into smaller ones. Initially I only focussed on forming a regex for Happy and needless to say also for any other sms variant of the word. And with python, my favourite and most powerful weapon in my arsenal yet, I formed the following regex:
- h+ - One or more occurrences of h.
- a* - Zero or more occurrences of a.
- p+ - One or more occurrences of p. Eg: happppyyy
- i* - Zero or more occurrences of i. Eg: hppiiiii!!
- y* - Zero or more occurrences of y. Eg: hppyyy..
- e* - Zero or more occurrences of e. Eg; haappeeee..
And I ran it against the data set. It failed to catch the following wishes:
many many happy returns of the day sensai. many many happy returns of the day many happy returns of the day :) many many happy returns of the day buddy hbd..sensei.. many happy return`s of the day netcamp wishes you a happy wala birthday wishes wish u many many happy returns of the day
The reason was quite clear. Happy may not be the first word. And it failed for such cases. So all I had to do was add a little ”.*“ before the regex, which essentially means anything before the regex. Thus I got this:
And this time it only missed out for the following:
But I couldn’t possibly rely on just this regex. Although my posts all but contained wishes only, it may not be the case always. There could be a post from a friend which could say:
Thanks for recommending Happy Days. Awesome watch!
Got the point right?
So I wrote one for Birthday and all other possible variants. It was:
What the hell is that! Wait I can explain it.
- .* - For anything before that regex.
- b - Match for the character b.
- [irthday] - To match birthday”
** ‘** - The pipe indicates an OR. So after b it will either look for irthday or ‘.
*(u(d+(a+e+ a+y+ y+)))** - I will break this down further:
- u* - Zero or more instances of “u”. Eg: buuddddayyy!
- d+ - At least one instance of “d”.
**(a+e+ a+y+ y+)** - Any one of the following:
- a+e+ - One or more occurrence of “a” and one or more occurrence of “e”. Eg: bdae.
- a+y+ - One or more occurrence of “a” and one or more occurrence of “y. Eg: bday.
- y+- One or more occurrence of “y”
I ran only this regex against the data set and it failed for these:
many many happy returns of the day sensai. many many happy returns of the day happy b.day...... many happy returns of the day :) many happy return`s of the day wishes wish u many many happy returns of the day
So it missed out for “happy returns of the day” type wishes with one exception. The third one - “happy b.day……“ So before moving on, I modified it to expect one of ‘ or . after b. Although you can skip this, a ”.” between “b” and “day” is actually rare. But I felt like doing it at the time. So for “birthday” I ended up with this:
Now I wrote another regex for “returns”, which is very simple:
Now I combined the above three regular expressions to form one that logically looked like this:
[Match "happy" and then look for either "birthday" or "returns"]
Thus the end product:
Now I ran this against my data set one last time and it missed out the following:
hbd..sensei.. many happy return`s of the day wishes
So I kept a manual override switch in my code for expressions for which my regex failed. Just a failsafe so I could manually force my code to comment a generous Thanks if it indeed was a birthday wish that my regex failed to match. Note the second one contains a back tick (`) and not a single quotation mark.
I am sure there is still some scope of refining the regex even futher for some corner case I may missed because in the end my tests are only limited by the data set I have. Please do let me know if you spot one! Until then, Happy Coding!comments powered by Disqus