C#•2y ago

❔ trim string according to regex

I've got this regex string, ^(?:\b\w+\b[\s\r\n]*){1,25}$ which is supposed to verify the string doesn't have more than 25 words. How do I use this regex (or modifications of it) to trim the string to 25 words if it's longer than that? (when the regex check fails)

42 Replies

Anton•2y ago

well remove the dollar sign, and then ig slice the rest the string with the help of the capture groups (they contain the start index information and such I think) or do ^(your_inner_expr)(.+)$ and then modify your match logic to check if the last group is empty and if it's not, then that's the rest of the string come to think of it, you could just slice off the match off of the original string, after removing the dollar from the regex ofc either way, you have to remove the dollar for any of that to work

Chris TCCOP•2y ago

I was thinking along these lines just chop off the end no need to split or anything the dollar sign is for prior logic I'll remove it for the string processing

Anton•2y ago

idk what you mean by splitting, but splitting by words might actually make your code way easier

Chris TCCOP•2y ago

really? I thought there would be a simple way to just use regex and delete anything that isn't the regex

Anton•2y ago

well I mean assuming you probably will need the words at some point

Chris TCCOP•2y ago

I just need the 25 anything except that doesn't matter to me

Anton•2y ago

if you split by words, you could do something along these lines:

var words = line.SplitterWords();
int i = 0;
var t = words.Skip(25);
using var e = t.GetEnumerator();
if (t.MoveNext())
    // use the words from t
else
    // no more words

var words = line.SplitterWords();
int i = 0;
var t = words.Skip(25);
using var e = t.GetEnumerator();
if (t.MoveNext())
    // use the words from t
else
    // no more words

Chris TCCOP•2y ago

I don't understand this code it uses enums?

Anton•2y ago

enumerators & enumerables and linq

Chris TCCOP•2y ago

uh I have no idea what those are

Anton•2y ago

are you a beginner?

Chris TCCOP•2y ago

very much also self-taught

Anton•2y ago

well an enumerable is a collection that you can loop through an enumerator is an object that holds the state of enumeration example: an enumerable can be an array, and an enumerator would be a struct with a reference to the array and the current index since enumerables are designed for enumeration, they can be lazily computed there's too much details to explain, you better read some docs or articles

Chris TCCOP•2y ago

I tried to learn enums on a few occasions I never understood them

Anton•2y ago

not enums enums have nothing to do with it enums is short for an enumeration

Chris TCCOP•2y ago

oh I thought enums are enumerators

Anton•2y ago

while these are a able and an ator do you know what constants and static classes are?

Chris TCCOP•2y ago

statics can't be changed no? read-only?

Anton•2y ago

not classes for classes it means they can't be instantiated and hence can only hold static things

Chris TCCOP•2y ago

yeah so read only right?

Anton•2y ago

what

Chris TCCOP•2y ago

as in, it's essentially like a book

Anton•2y ago

Chris TCCOP•2y ago

you can read from it but can't change the values

Anton•2y ago

yeah you seem to not know classes either yet well I suggest you do some reading find some book maybe

Chris TCCOP•2y ago

all my C# experience is programming some mobile app prototypes in unity and using it as a scripting language

Anton•2y ago

you can't make more or less complicated systems without this knowledge tho well if it's simple scripts I guess you'll manage but if you ever want to go beyond, take your time

Chris TCCOP•2y ago

hm. as of now I've only been doing very simple things for the past 6 years So is it possible to truncate a string based on number of words? as of now, the only way I could think of would be to just split the string, then stitch them together again, then ditch the remaining array indices

Anton•2y ago

the pseudocode would be kinda like this

var regex = ...;
string? match = regex.GetMatch(input);
if (match is not null)
    return input[match.Length ..];

var regex = ...;
string? match = regex.GetMatch(input);
if (match is not null)
    return input[match.Length ..];

Chris TCCOP•2y ago

but length is in characters not words would I have to use regex to split the string into words first?

Anton•2y ago

well yeah that's what you need there you wanted everything after the first 25 words

Chris TCCOP•2y ago

but words can have different character amounts, no?

Anton•2y ago

explain your logic

Chris TCCOP•2y ago

"purple" and "christmas" have different character amounts so you can't really use character amounts to determine where a word boundary is, right?

Anton•2y ago

I don't see why that would matter in your problem you just needed to slice off the first 25 words, you said

Chris TCCOP•2y ago

I want to keep the first 25 words and slice off the rest sorry if I wasn't clear with my wording

Anton•2y ago

well then just take the match from the regex the first group is the whole match

Chris TCCOP•2y ago

string match = filter.Match(string);
print match;

string match = filter.Match(string);
print match;

Anton•2y ago

I don't remember the API exactly, you have to look that up I almost never use regexes

Florian Voß•2y ago

I think you shouldn't be solving this with regex in the first place just check if length or count is greater than 25? after splitting the string on what ever seperates the words from each other

Chris TCCOP•2y ago

that was the other option that I saw yeah

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ trim string according to regex