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Regex character "$" doesn't mean "end-of-string"

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Re: Regex character "$" doesn't mean "end-of-string"

#351

Post by wlonkly »

TristanBall wrote: post #332
emporas wrote: post #324

Earlier quoted context omitted.

Regexes originate from Perl, or they were popularized by Perl if i got this right. In Perl readable code is not ranked as one of it's top 100 priorities. Regexes could originate from J and situation could be even worse though!

Regex's predate perl quite substantially. Think grep and friends if nothing else. Certainly making the perlre library available separate to perl encouraged its widespread use, and lots of others copied or were inspired by it. "Popularized" doesn't seem like quite the right word though, I don't disagree with the point, but if I shout "Hey everyone let's write regex's" at the office people throw stationary at me, which…

Perl spread regexes.

Re: Regex character "$" doesn't mean "end-of-string"

#352

Post by emporas »

wlonkly wrote: post #351
TristanBall wrote: post #332

Earlier quoted context omitted.

Regex's predate perl quite substantially. Think grep and friends if nothing else. Certainly making the perlre library available separate to perl encouraged its widespread use, and lots of others copied or were inspired by it. "Popularized" doesn't seem like quite the right word though, I don't disagree with the point, but if I shout "Hey everyone let's write regex's" at the office people throw stationary at me, which…

Perl spread regexes.

Super spreader event we've got ourselves into.

I took a look at Raku, which claims be a better Perl maybe, or closely related but more modern, it certainly looks nice. Although i am a big fan of typed languages, Raku piqued my interest.

Re: Regex character "$" doesn't mean "end-of-string"

#353

Post by [deleted] »

sltkr wrote: post #315
danbruc wrote: post #305

Earlier quoted context omitted.

Python's behavior is not a hack, it is the common behavior. $ matches at the end of the string or before the last character if that is a newline, which is logically the same as the end of a single line. But as you said, you can have additional newlines inside of the string which is also the common behavior and not specific to python. Personally I think of this as you just assume that the string is a single line and m…

> Python's behavior [..] is the common behavior. The very post we're commenting on shows that that's not true: PHP, Python, Java and .NET (C#) share one behavior (accept "\n" as "$"), and ECMAScript (Javascript), Golang, and Rust share another behavior (do not accept "\n" as $). Let's not argue about which is “the most common”; all of these languages are sufficiently common to say that there is no single common behav…

[deleted]

Re: Regex character "$" doesn't mean "end-of-string"

#354

Post by gordonfish »

saghm wrote: post #334
gordonfish wrote: post #326

Earlier quoted context omitted.

> I guess it shows how far off the radar Perl currently is. This is a serious misconception. Perl is far, far from dead. The constant activity of the gargantuan CPAN library more than demonstrates very much the opposite. I would say Perl and its community has done quite well considering it hasn't had the same mountain of corporate funds thrust into it like more highlighted have. Mainstream ain't everything.

I don't think "off the radar" means dead, but that people aren't generally aware of what's going on with it. I think this is actually pretty consistent with what you're saying; stuff is going on with it, but it's not on people's radar, so they don't realize it.

Fair enough point.

Re: Regex character "$" doesn't mean "end-of-string"

#355

Post by Dylan16807 »

denzquix wrote: post #211
vitiral wrote: post #202

In Lua it's only the start/end of the string > A pattern is a sequence of pattern items. A caret '^' at the beginning of a pattern anchors the match at the beginning of the subject string. A '$' at the end of a pattern anchors the match at the end of the subject string. At other positions, '^' and '$' have no special meaning and represent themselves. https://www.lua.org/manual/5.3/manual.html#6.4.1 Lua's pattern matc…

> In Lua it's only the start/end of the string There's an additional caveat: if you use the optional "init" parameter to specify an offset into the string to start matching, the ^ anchor will match at that offset , which may or may not be what you expect.

> which may or may not be what you expect

I find it hard to imagine any other expectation passing the rubber duck test.

"Oh, so you expected the match to always fail, no matter what the string was?"

Re: Regex character "$" doesn't mean "end-of-string"

#356

Post by lizmat »

emporas wrote: post #352
wlonkly wrote: post #351

Earlier quoted context omitted.

Perl spread regexes.

Super spreader event we've got ourselves into. I took a look at Raku, which claims be a better Perl maybe, or closely related but more modern, it certainly looks nice. Although i am a big fan of typed languages, Raku piqued my interest.

In Raku, if you want to go typed, you can! It's called "gradually typed".

my Int $a = 42; # ok

my Int $a = "foo"; # Type check failed in assignment to $a; expected Int but got Str ("foo")

Re: Regex character "$" doesn't mean "end-of-string"

#357

Post by keybored »

jkrejcha wrote: post #340
keybored wrote: post #244

Earlier quoted context omitted.

Why did they even decide to use two characters for the end of line? Seems bizarre. I could have imagined that `\r` and `\n` was a tossup. But why both?

Carriage Return (\r) - move to start of line Line Feed (\n) - move down 1 line Essentially, when you're sending commands to teletypes, that's how you'd have to do it.

I know what the symbols mean and their original purpose. No one has answered why Windows and apparently only Windows acts like this. It’s not like Windows is the only platform that cares about hysterical raisins.

Re: Regex character "$" doesn't mean "end-of-string"

#358

Post by rusk »

psd1 wrote: post #339
ykonstant wrote: post #79

Earlier quoted context omitted.

I am pretty sure even pure Awk can do it; or am I mistaken? I thought there was an even more sophisticated example in the Awk book. Edit: oh, you mean via regex engines available in GNU tools; I am dumb. Hmm... is there no GNU extension with PCRE?

Nope. Gnu regex tools also do not support lookahead or alternation. Lookahead is really useful. It's a problem for Linux that it can't move on. The cold dead hand of gnu is firmly around the community's neck.

> the cold dead hand …

Android, Busybox and Muscl have entered the chat

Re: Regex character "$" doesn't mean "end-of-string"

#359

Post by denzquix »

Dylan16807 wrote: post #355
denzquix wrote: post #211

Earlier quoted context omitted.

> In Lua it's only the start/end of the string There's an additional caveat: if you use the optional "init" parameter to specify an offset into the string to start matching, the ^ anchor will match at that offset , which may or may not be what you expect.

> which may or may not be what you expect I find it hard to imagine any other expectation passing the rubber duck test. "Oh, so you expected the match to always fail, no matter what the string was?"

Well, it's not a completely outlandish scenario that the value of `init` might come from a variable that is sometimes at the start of the string and sometimes not, and a newcomer might expect `^` to only match when it is.

Don't get me wrong, it's certainly far more useful as it is, I'm glad it works this way.

Re: Regex character "$" doesn't mean "end-of-string"

#360

Post by emporas »

lizmat wrote: post #356
emporas wrote: post #352

Earlier quoted context omitted.

Super spreader event we've got ourselves into. I took a look at Raku, which claims be a better Perl maybe, or closely related but more modern, it certainly looks nice. Although i am a big fan of typed languages, Raku piqued my interest.

In Raku, if you want to go typed, you can! It's called "gradually typed". my Int $a = 42; # ok my Int $a = "foo"; # Type check failed in assignment to $a; expected Int but got Str ("foo")

Very nice, good to know. Yes i know gradual typing, Python has a form of that i think. I will check out Raku at some point, the type system will not go unnoticed. I didn't even know it had one!
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