[ruby-core:78903] [Ruby trunk Bug#13082] Regex match from position behavior with start of line/string special character

Issue #13082 has been updated by Vincent Woo.


Thanks, I didn't know about \G! It's a little hard to understand in this situation, do you think it might be helpful to add to the doc on matching with position?

"\G - Matches point where last match finished"

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Bug #13082: Regex match from position behavior with start of line/string special character
https://bugs.ruby-lang.org/issues/13082#change-62314

* Author: Vincent Woo
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.4.0p0 (2016-12-24 revision 57164) [x86_64-darwin16]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
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Hello,

Apologies in advance if this question was addressed already, I could not find any information on it.

Regexp#match [provides this behavior](https://ruby-doc.org/core-2.4.0/Regexp.html#method-i-match):

> If the second parameter (pos) is present, it specifies the position in the string to begin the search.

So, if you run:

`/test/.match "a test", 2`

it will return a match. This becomes an issue when you try to write a regex to match "if the pattern begins at the specified point in the string".

`/^test/.match "a test", 2`

Does not return a match. Using `\A` does not work either. It's an open question whether this *should* work, but I think it should. I would expect calling match with a position to treat the string passed in as essentially truncated up to that point.

I should add that the reason I want it to work this way is that queries like

`/test/.match "a longer test", 2`

will return a match. My real goal is to find if `/test/` *starts* at position 2, so I do need the special line/string start character.

What do you think?

Cheers,
Vincent



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