Contents
Why you should avoid regex?
When Not to Use Regex Regular expressions can be a good tool, but if you try apply them to every situation, you’ll be in for a world of hurt and confusion down the line. Regex isn’t suited to parse HTML because HTML isn’t a regular language. Regex probably won’t be the tool to reach for when parsing source code.
When should I use regular expression?
Regular expressions are useful in search and replace operations. The typical use case is to look for a sub-string that matches a pattern and replace it with something else. Most APIs using regular expressions allow you to reference capture groups from the search pattern in the replacement string.
How do you prove a language is regular?
To prove if a language is a regular language, one can simply provide the finite state machine that generates it. If the finite state machine for a given language is not obvious (and this might certainly be the case if a language is, in fact, non-regular), the pumping lemma for regular languages is a useful tool.
Are regular expressions worth it?
Regular Expressions are VERY powerful and a valuable tool. Use them but use them carefully, and think about how to make it clear what the intent of the regular expression is. With great power comes great responsibility! Regular expressions are great, but there can be a tendancy to over-use them!
What is type1 grammar?
According to Chomsky hierarchy, grammars are divided of 4 types: Type 0 known as unrestricted grammar. Type 1 known as context sensitive grammar. Type 2 known as context free grammar. Type 3 Regular Grammar.
When to use regular expressions and how to use them?
Regular expressions (or regex) are incredibly helpful tools to have at your disposal as a software developer, but they’re often dangerous tools. In this post, I’m going to focus on the times where you shouldn’t use regex, and then I’ll go over some strategies and features to use when you do write regular expressions.
Can You parse HTML with only regular expressions?
So when you hear that HTML or C# cannot be parsed by regular expressions, be aware that regular expressions still are a critical part of the parsers. You just cannot parse such language using only regular expressions and no helper code. Not the answer you’re looking for?
Why do people ask for regexes on Stackoverflow?
On stackoverflow one often sees people ask for regexes that find out whether a given string does not contain this or that. This is, IMHO, reversing the purpose of regular expression.
Is it better to use regex or program logic?
This is, IMHO, reversing the purpose of regular expression. Even if a solution exists (employing negative lookbehind assertions or such stuff), it is often much better to use the regex for what it was made for and handle the negative case with program logic.