Regex: undocumented feature?

ruby-talk
1

p /\AQ/ =~ “aQ” # ==> nil
p /\A=|Q/ =~ “aQ” # ==> 1

2

Apparently, Joel VanderWerf recently wrote:

p /\AQ/ =~ “aQ” # ==> nil
p /\A=|Q/ =~ “aQ” # ==> 1

\A means beginning of the string (mostly the same as ^, except in
multiline mode), and it is lower precidence than |

Notice:

p /^Q/ =~ “aQ” # ==> nil
p /^=|Q/ =~ “aQ” # ==> 1

But:

p /^(=|Q)/ =~ “aQ” # ==> nil
p /\A(=|Q)/ =~ “aQ” # ==> nil

At least with ruby 1.6.8 :wink:

Wes

3

Wesley J. Landaker wrote:

Apparently, Joel VanderWerf recently wrote:

p /\AQ/ =~ “aQ” # ==> nil
p /\A=|Q/ =~ “aQ” # ==> 1

\A means beginning of the string (mostly the same as ^, except in
multiline mode), and it is lower precidence than |

Ah, thanks. I always expect | to have a higher prec than most other things.

4

“Joel VanderWerf” vjoel@PATH.Berkeley.EDU schrieb im Newsbeitrag
news:3EE8F814.5010101@path.berkeley.edu…

Wesley J. Landaker wrote:

Apparently, Joel VanderWerf recently wrote:

p /\AQ/ =~ “aQ” # ==> nil
p /\A=|Q/ =~ “aQ” # ==> 1

\A means beginning of the string (mostly the same as ^, except in
multiline mode), and it is lower precidence than |

Ah, thanks. I always expect | to have a higher prec than most other
things.

??? That’s exactly what Wesley wrote. Then I don’t understand your
initial question.

robert
5

I said lower precedence, but I really meant higher. (I was thinking
backwards as I typed that out, probably :wink:

The key, I think, was that that the expression was being evaluated
relation to | differently than the OP was expecting. =)

···

On Friday 13 June 2003 4:32 am, Robert Klemme wrote:

“Joel VanderWerf” vjoel@PATH.Berkeley.EDU schrieb im Newsbeitrag
news:3EE8F814.5010101@path.berkeley.edu…

Wesley J. Landaker wrote:

Apparently, Joel VanderWerf recently wrote:

p /\AQ/ =~ “aQ” # ==> nil
p /\A=|Q/ =~ “aQ” # ==> 1

\A means beginning of the string (mostly the same as ^, except in
multiline mode), and it is lower precidence than |

Ah, thanks. I always expect | to have a higher prec than most other

things.

??? That’s exactly what Wesley wrote. Then I don’t understand your
initial question.

–
Wesley J. Landaker - wjl@icecavern.net
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