<Write Your Own Regular Expression Parser ⁄ >

Have you ever wondered how regular expressions work in detail? If the answer is yes, this article is right for you. I will try to guide you step by step on how to create your own mini regular expression library. The purpose of the article is NOT to give you a highly optimized, tested, and great regular expression library, but to explain the principles behind the pattern matching in text files. If you only want a good library and don't care how it works, you probably want boost the regex library, which you can find here. I used a couple of different regular expression libraries but I must say that I am happiest with boost regex. Obviously, you decide for yourself. There is another regular expressions article that could be found here. I must admit I did not read the article completely, but it seems to me that the article focuses mostly on how to use a regular expression library provided by the author. In this article, the author uses a similar technique (I could be wrong, though) to create a more sophisticated library. The aticle you are reading right now could be seen as a prerequisite for the article I just mentioned above.

Regular expressions are part of the MS.NET library or Java SDK (if you write code in Java). As you can see, regular expressions are available in many different programming languages and technologies. Actually, the article does not focus on writing the library in a specific language. I wrote the code in C++, using STL primarily because it is my favorite language/library, but the principles from the article could be applied to any language (obviously). I will try to be as language independent as possible using pseudo code wherever possible. If you want the code in Java, please send me an e-mail. The code provided in this article is free (obviously), but if you like it and use it in your application, it would be great if you would give me the credit for what I deserve. Also please e-mail me, so I can show off to my peers and/or potential employers.



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