Constructing regex

Question

Hi,

I use regex buddy which takes in a regex and then gives out the meaning of it from which one gets what it could be doing? On similar lines is it possible to have some engine which takes natural language input describing about the pattern one needs to match/replace and gives out the correct(almost correct) regex for that description?

e.g. Match the whole word 'dio' in some file

So regex for that could be : <dio> or

\bdio\b

-AD.

P.S. = I think few guys here might think this as a 'subjective' 'not-related-to-programming' question, but i just need to ask this question nonetheless. For myself. - Thanks.

Answer 1

Yeah, I agree with you that it is subjective. But I will answer your question because I think that you have asked a wrong question.

The answer is "YES". Almost anything can be coded and this would be a rather simple application to code. Will it work perfectly? No, it wouldn't because natural language is quite complex to parse and interpret. But it is possible to write such an engine with some constraints.

Answer 2

This would be complicated to program, because you need a natural language parser able to derive meaning. Unless you limit it to a strict subset -- in which case, you're reinventing an expression language, and you'll eventually wind up back at regular expressions -- only with bigger symbols. so what's the gain?

Regexes were developed for a reason -- they're the simplest, most accurate representation possible.

There is a Symbolix Regular Expression Builder package for Emacs, but looking at it, I think that regular expressions are easier to work with.

Answer 3

Short answer: no, not until artificial intelligence improves A LOT.

If you wrote something like this, you'd have a very limited syntax. For someone to know "Match the whole word 'dio' in some file", they would basically need to have significant knowledge of regular expressions. At that point, just use regular expressions.

For non-technical users, this will never work unless you limit it to basic "find this phrase" or, maybe, "find lines starting/ending with ??". They're never going to come up with something like this:

Find lines containing a less-than symbol followed by the string 'img' followed by one or more groupings of: some whitespace followed by one or more letters followed by either a double-quoted string or a single-quoted string, and those groupings are followed by any length of whitespace then a slash and a greater-than sign.

That's my attempt at a plain-language version of this relatively simple regex:

/<img(\s+[a-z]+=("[^"]*"|'[^']*'))+\s*/>/i

Answer 4

Generating a regex via the use of a natural language processor is quite possible. Prolog is supposed to be a good language choice for this kind of problem. In practice, however, what you'd be doing, in effect, is designing your own input language which provides a regex as output. If your goal is to produce regexs for a specific task, this might in fact be useful. Perhaps the task you are doing tends to require certain formulations that are doable but not built into regular expressions. Though whether this will be more effective than just creating the regexs one at a time depends on your project. Usually this is probably not the case, since your own language is not going to be as well-known or as well-documented as regex. If your goal is to produce a replacement for regex whose output will be parsed as a regex, I think you're asking a lot. Not to say people haven't done the same sort of thing before (e.g. the C++ language as an 'improvement' that runs, originally, on C++).