Bug #7092
closedStringScanner start-of-line matches false positives, while lookbehind for a newline gives false negatives
Description
To reproduce:
>> require 'strscan'
>> ss = StringScanner.new("ab")
>> ss.scan(/./)
=> "a"
>> ss.scan(/^./) # expecting nil, since the head is in the middle of a line
=> "b"
As a workaround-that-didn't-work, I also tried looking behind for a newline, which seems never to match, even with the m
flag.
>> ss = StringScanner.new("a\nb")
>> ss.scan(/../m)
=> "a\n"
>> ss.scan(/(?<=\n)./m) # expecting "b", since the previous char is a newline
=> nil
Updated by jayferd (Jay Adkisson) almost 12 years ago
Bump. Can someone confirm whether or not this is expected behavior?
Updated by jayferd (Jay Adkisson) almost 12 years ago
I've now reproduced this in 2.0.0-preview1. Is anyone out there...?
Updated by mame (Yusuke Endoh) almost 12 years ago
- Status changed from Open to Feedback
- Assignee set to mame (Yusuke Endoh)
- Target version set to 2.0.0
Sorry for late reply.
Honestly, it is difficult to say whether it is intended or a bug because there is no strscan maintainer.
But since 1.8, StringScanner#scan has behaved so. I guess there is some existing programs that depends on the behavior.
Therefore, I'd like not to change the behavior unless there is no special reason.
Do you have any special reason? Or do you just want to confirm?
--
Yusuke Endoh mame@tsg.ne.jp
Updated by mame (Yusuke Endoh) almost 12 years ago
FYI: You may want to use StringScanner#beginning_of_line?.
--
Yusuke Endoh mame@tsg.ne.jp
Updated by nobu (Nobuyoshi Nakada) almost 12 years ago
I guess it would be intentional.
'^' and '\A' are `beginning of the target' (and beginning of a line for ^) anchors, so seems reasonable that it matches the beginning of the part to be matched.
Updated by mame (Yusuke Endoh) over 11 years ago
- Priority changed from Normal to 3
- Target version changed from 2.0.0 to 2.6
Updated by mame (Yusuke Endoh) about 11 years ago
- Status changed from Feedback to Rejected
I'm marking this ticket as closed due to no feedback.
--
Yusuke Endoh mame@tsg.ne.jp