(?:)
It is a valid ruby regular expression, could anyone tell me what it means?
Thanks
+3
A:
It will not capture the part of the matching string in a backreference (i.e \1).
gpojd
2009-02-23 16:31:37
@gpojd, How should I understand the '?' and ':' here?
eric2323223
2009-02-23 16:34:03
For example, (\d+) will capture consecutive digits in a backreference like \1. If you want to group part of the regex, but do not want to capture them, you would use (?:\d+). Needlessly capturing the data can decrease performance.
gpojd
2009-02-23 16:36:54
+2
A:
This is an empty, non-capturing group. It has no meaning in this case and can be dropped.
Gumbo
2009-02-23 16:32:43
+9
A:
Like others have said, it's used as the non-capturing syntax for a regex, but, it's also valid ruby syntax outside of a regex.
In ruby ?: is the integer value for the colon character:
% irb
irb> ?:
=> 58
irb ":"[0]
=> 58
Adding parenthesis doesn't change the value: (?:) == ?:
When you add spaces (? :), it's the ternary operator, which is essentially shorthand for if/then/else in ruby, so the statement ( bool ? truish : falsy ) is equivalent to
if bool then
truish
else
falsy
end
rampion
2009-02-23 17:59:30