Comment by icsa
4 years ago
And yet regular expressions are a part of most programming languages as a library or built-in syntax.
Why is that?
4 years ago
And yet regular expressions are a part of most programming languages as a library or built-in syntax.
Why is that?
Probably due to they're a great notation for the problem area which for regex is concisely describing text patterns.
For example 'a*b' is any number of 'a's followed by 'b'.
How else would you concisely state that?
How else would you concisely state that?
Presumably people who hate array languages think all 3 character regexes should instead be big nested loops, so they are "readable".
Regexes in the Unix tradition are a user interface as much as a programming language. Not that there's a sharp distinction, but it's almost a trite observation that regexes per se shine for ad hoc string searching but show their weakness when they start becoming parts of programs.
When writing a program, I prefer to use a PEG, giving the less compact notation `'a'* 'b'` but also letting me say `'a'* b` and define b as its own rule, including recursion for the useful cases. It helps that it's more powerful, being little more than a formalization of the post-regular strategies used in Perl-style 'regular' expressions while embracing recursion.
For '/' in vim, grep, wherever? Yeah regex is fine, that's what it was designed for.
I can't remember the names but I've seen at least two alternative syntaxes recently that are a lot more readable. At least one of them fixed the issue of regex mixing up control in-band with data. So your example would be something like
Much more readable and less error-prone.
> the issue of regex mixing up control in-band with data
Could you explain this? I don't quite understand what the problem is. Do you mean something like sed's regex substitute command?
2 replies →
They're very quick to write and they (in appropriate cases) would be quite difficult to implement otherwise (tedious state machine stuff). They are still massively overused though. Using a regex at all is a huge red flag. Sometimes they are appropriate, but not in 90% of cases in my experience.
Anyway I'm not sure the same is true for K. At least for the given example the for loop was not exactly difficult to write.