Problem regarding regular expression

[Stanford Ng]

puts( /^[a-z 0-9]*$/ =~ 'Well hello 123' ) # no match due to ^ and
uppercase 'W'


puts( /^[a-z 0-9]*/ =~ 'Well hello 123' ) # * zero (or more) matches at
start ^ = 0

i could barely understand why the existence of $ makes such a
difference.
any help?

 

[Stanford Ng]

puts( /[a-z 0-9]*$/ =~ 'Well hello 123' ) # no ^, so match made at char
1 'e'

puts( /[a-z 0-9]$/ =~ 'Well hello 123' ) # $ match from end = 13
so as this one,why does * makes such a difference?

 

[Victor Deryagin]

i could barely understand why the existence of $ makes such a

difference.
any help?

/^[a-z 0-9]*$/ must match the whole string (and it can't due to
uppercase 'W'

/^[a-z 0-9]*/ may match only empty string at the beginning (and it does)

 

[Victor Deryagin]

puts( /[a-z 0-9]$/ =~ 'Well hello 123' ) # $ match from end = 13

so as this one,why does * makes such a difference?

Without * regexp may match only one char at the end of the string.

 

[Josh Cheek]

[Note: parts of this message were removed to make it a legal post.]

puts( /^[a-z 0-9]*$/ =~ 'Well hello 123' ) # no match due to ^ and
uppercase 'W'


puts( /^[a-z 0-9]*/ =~ 'Well hello 123' ) # * zero (or more) matches at
start ^ = 0

i could barely understand why the existence of $ makes such a
difference.
any help?

Why don't you play with it at rubular.com for a while, it will help you to
see easier what is happening when you change your regexp.

http://rubular.com/r/2f1DxHl33E

 

[Stanford Ng]

dudes,i am really confused with this.
could someone elaborate more on this?
/^\s*#/

 

[Stanford Ng]

pal,i think i need more elaborate on these two expressions if possible.
/^[a-z]*/
/[a-z]*$/
please

 

[Josh Cheek]

[Note: parts of this message were removed to make it a legal post.]

dudes,i am really confused with this.
could someone elaborate more on this?
/^\s*#/

Could you elaborate on what has you confused? What do you expect it to
match? What text are you matching it against? What methods are using it and
how are you calling them?

 

[Stanford Ng]

i think i roughly understand by now.
thanks for your help

 

[Ammar Ali]

pal,i think i need more elaborate on these two expressions if possible.
/^[a-z]*/
/[a-z]*$/
please

This might help. The following two expressions are matching the same thing:

'Well hello 123' =~ /^[a-z]*/ => 0
'Well hello 123' =~ /^/

=> 0

Same here:

'Well hello 123' =~ /[a-z]*$/ => 14
'Well hello 123' =~ /$/

=> 14

For more details, take a look at the matched data

/^[a-z]*/.match('Well hello 123').to_a => [""]
/[a-z]*$/.match('Well hello 123').to_a

=> [""]

HTH,
Ammar

 

[Robert Klemme]

pal,i think i need more elaborate on these two expressions if possible.
/^[a-z]*/
/[a-z]*$/
please

Please don't write "need" and ask specific questions. It's just too
broad a question you are posing here. People could write books in
answer to this. See also:

http://www.catb.org/~esr/faqs/smart-questions.html

Kind regards

robert