Regular expression match

Ruby
#1

Hi,

Can anyone explain to me this regular expression, please:
str[/\A([a-z]\w*)/, 1]

what’s the use of 1 in this expression
regards,

#2

Hello,

This syntax is used to return the matching portion of supplied regxp.
For
example:

“hello world”[/(\w+)(\s)(\w+)/, 0] #=> “hello world”
“hello world”[/(\w+)(\s)(\w+)/, 1] #=> “hello”
“hello world”[/(\w+)(\s)(\w+)/, 2] #=> " "
“hello world”[/(\w+)(\s)(\w+)/, 3] #=> “world”

#3

On Nov 21, 2011, at 11:02 PM, rubix Rubix wrote:

Hi,

Can anyone explain to me this regular expression, please:
str[/\A([a-z]\w*)/, 1]

Check out the documentation:

ri String#[]

When given a regular expression and a fixnum, you’re matching the string
against the regular expression and returning the capturing group
indicated by the fixnum. That is to say, your example will match a word
beginning with a lower case letter at the beginning of the string. Since
\A is an anchor and therefore not part of the matched string and if I am
not mistaken, your expression is actually equivalent to just

str[/\A[a-z]\w*/]

If there is a particular reason for using the capturing group over the
entire expression there you should probably add a comment to document
it!

Sylvester

#4

Thank you for your answer
I am using this code to parse a text to search the first word and see if
the word is one of the words of an array of strings and then increment
an index with the size of the word to parse the rest of the text
It is working good but when I try it with unicode characters, I obtain
the letters of the first word and not the hole first word:
str[/[\u0627-\u064A]+/,1]

best regards,

#5

On Mon, Nov 21, 2011 at 11:55 PM, rubix Rubix [email protected]
wrote:

I am using this code to parse a text to search the first word and see if
the word is one of the words of an array of strings and then increment
an index with the size of the word to parse the rest of the text

Sounds like you rather want String#scan.

It is working good but when I try it with unicode characters, I obtain
the letters of the first word and not the hole first word:
str[/[\u0627-\u064A]+/,1]

Maybe your range is missing something. I’d rather use specific
character classes for this anyway:

str.scan /\p{Word}+/ do |word|
printf “Found word: %p\n”, word
end

http://www.geocities.jp/kosako3/oniguruma/doc/RE.txt

Kind regards

robert