Why you shouldnt use regex?

When Not to Use Regex Using them is essentially like injecting a small programming language into another programming language. This is a significant level of complexity to introduce when you’re looking for some text parsing. Regex probably won’t be the tool to reach for when parsing source code.

Is it necessary to learn regex?

Regular Expressions, also known as Regex, come in handy in a multitude of text processing scenarios. Regex defines a search pattern using symbols and allows you to find matches within strings. Most text editors also allow you to use Regex in Find and Replace matches in your code. …

Are Regexes fast?

Regular expressions are one possible type of parser, and for the standard case they do parse the string letter by letter (they never require contextual information), so the question is a little unclear. But at least in theory, true regular expressions are very fast indeed.

What are regular expressions used for?

Regular expressions are used in search engines, search and replace dialogs of word processors and text editors, in text processing utilities such as sed and AWK and in lexical analysis. Many programming languages provide regex capabilities either built-in or via libraries, as it has uses in many situations.

Is regex a Turing machine?

So, no, regular languages aren’t Turing-complete. Regular languages (which regular expressions are expressions of) can be processed by a finite-state machine (by a simple table of state/input transitions, if you will).

Is regex bad for performance?

In General, the Longer Regex Is the Better Regex Good regular expressions are often longer than bad regular expressions because they make use of specific characters/character classes and have more structure. This causes good regular expressions to run faster as they predict their input more accurately.

Are regular expressions easy or hard to learn?

Regular expressions are easy to learn but difficult to master. You don’t need to learn everything about it to start using it. Just be sensible about it. You need to know about the technology so that you can make a good decision on when to use it. I work in an embedded code base that does not have a regular expression library available.

Why is it so hard to debug regular expressions?

One “run” of a regular expression is effectively an atomic operation. It’s hard to observe stepwise execution in a debugger. It’s too easy to write a regular expression that accidentally accepts more input than you intend. The value of a regular expression isn’t really to match valid input, it’s to fail to match invalid input.

Why don’t we use regular expressions in C++?

Regular expressions do not support this working style very well. One “run” of a regular expression is effectively an atomic operation. It’s hard to observe stepwise execution in a debugger. It’s too easy to write a regular expression that accidentally accepts more input than you intend.

Is it true that regexes are slow?

And yes, regexes can be extremely extremely slow compared to using simple functions. And not just slow, but the performance of the regex engine can be totally unpredictable when faced with arbitrary (user-supplied) inputs.