Hello,
I tried to grep from a string, but got wrong.
irb(main):010:0* x = "hello world baby girl"
=> "hello world baby girl"
irb(main):011:0>
irb(main):012:0*
irb(main):013:0* x.grep(/hello/)
NoMethodError: undefined method `grep' for "hello world baby girl":String
from (irb):13
from /usr/bin/irb:12:in `<main>'
where shall 'grep' method come from?
thanks~
Grep is not defined on Ruby 1.9-Strings.
It was on Ruby 1.8-Strings, but only because they were belonging to the group of objects that mixed in Enumerable.
There, grep behaves like this (line by line):
x = "hello world baby girl"
x.grep(/hello/)
#=> ["hello world baby girl"]
x = "hello\nworld\nbaby\ngirl"
x.grep(/hello/)
#=> ["hello\n"]
The same can be done in Ruby 1.9 by just splitting the String beforehand. Arrays are Enumerable and thus
still have grep:
x = "hello\nworld\nbaby\ngirl"
x.split("\n").grep(/hello/)
#=> ["hello"]
Note the absence of the line-break which might be intended or not :).
Regards,
Florian Gilcher
On Nov 27, 2009, at 11:26 PM, Ruby Newbee wrote:
Hello,
I tried to grep from a string, but got wrong.
irb(main):010:0* x = "hello world baby girl"
=> "hello world baby girl"
irb(main):011:0>
irb(main):012:0*
irb(main):013:0* x.grep(/hello/)
NoMethodError: undefined method `grep' for "hello world baby girl":String
from (irb):13
from /usr/bin/irb:12:in `<main>'where shall 'grep' method come from?
thanks~
- --
Florian Gilcher
smtp: flo@andersground.net
jabber: Skade@jabber.ccc.de
gpg: 533148E2
Thanks, that sounds be more reasonable, b/c I like to grep from an
array not a string (yes perl does this).
btw, why 0/0 got failed but 0.0/0.0 seems valid?
irb(main):144:0> v=0/0
ZeroDivisionError: divided by 0
from (irb):144:in `/'
from (irb):144
from /usr/bin/irb:12:in `<main>'
irb(main):145:0> v=0.0/0.0
=> NaN
2009/11/28 Florian Gilcher <flo@andersground.net>:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1Grep is not defined on Ruby 1.9-Strings.
It was on Ruby 1.8-Strings, but only because they were belonging to the
group of objects that mixed in Enumerable.There, grep behaves like this (line by line):
x = "hello world baby girl"
x.grep(/hello/)
#=> ["hello world baby girl"]
x = "hello\nworld\nbaby\ngirl"
x.grep(/hello/)
#=> ["hello\n"]The same can be done in Ruby 1.9 by just splitting the String beforehand.
Arrays are Enumerable and thus
still have grep:x = "hello\nworld\nbaby\ngirl"
x.split("\n").grep(/hello/)
#=> ["hello"]
Hi --
On Sat, 28 Nov 2009, Florian Gilcher wrote:
Grep is not defined on Ruby 1.9-Strings.
It was on Ruby 1.8-Strings, but only because they were belonging to the group of objects that mixed in Enumerable.
There, grep behaves like this (line by line):
x = "hello world baby girl"
x.grep(/hello/)
#=> ["hello world baby girl"]
x = "hello\nworld\nbaby\ngirl"
x.grep(/hello/)
#=> ["hello\n"]The same can be done in Ruby 1.9 by just splitting the String beforehand. Arrays are Enumerable and thus
still have grep:x = "hello\nworld\nbaby\ngirl"
x.split("\n").grep(/hello/)
#=> ["hello"]Note the absence of the line-break which might be intended or not :).
I would probably do this in 1.9:
string.lines.grep(/pattern/)
where lines returns an enumerator.
David
--
THE COMPLEAT RUBYIST, Ruby training with Black/Brown/McAnally!
January 22-23, Tampa, Florida
Info and registration at http://www.thecompleatrubyist.com
--------------------------------------
My new job: http://tinyurl.com/yfpn9hz
From: Ruby Newbee [mailto:rubynewbee@gmail.com]
Thanks, that sounds be more reasonable, b/c I like to grep from an
array not a string (yes perl does this).btw, why 0/0 got failed but 0.0/0.0 seems valid?
irb(main):144:0> v=0/0
ZeroDivisionError: divided by 0
from (irb):144:in `/'
from (irb):144
from /usr/bin/irb:12:in `<main>'irb(main):145:0> v=0.0/0.0
=> NaN
It's the difference betweeen floating point and integer arithmetic.
When working with integers all results must be valid integers, whereas
floating point can represent NaN (Not a Number), negative zero,
and infinity and negative infinity:
irb(main):001:0> 1.0/0.0
=> Infinity
irb(main):002:0> -0.0
=> -0.0
irb(main):003:0> 0.0/-0.0
=> NaN
irb(main):004:0> -1.0/0.0
=> -Infinity
irb(main):005:0>
See Floating-point arithmetic - Wikipedia for more information.
Jep, there is always room to improve. It also maps better to the old behaviour where you were basically grepping #each_line.
Thanks,
Florian
On Nov 28, 2009, at 3:57 AM, David A. Black wrote:
The same can be done in Ruby 1.9 by just splitting the String beforehand. Arrays are Enumerable and thus
still have grep:x = "hello\nworld\nbaby\ngirl"
x.split("\n").grep(/hello/)
#=> ["hello"]Note the absence of the line-break which might be intended or not :).
I would probably do this in 1.9:
string.lines.grep(/pattern/)
where lines returns an enumerator.
David
Why not just string.scan(/pattern/) ?
Kind regards
robert
On 11/28/2009 08:27 AM, David A. Black wrote:
Hi --
On Sat, 28 Nov 2009, Florian Gilcher wrote:
Grep is not defined on Ruby 1.9-Strings.
It was on Ruby 1.8-Strings, but only because they were belonging to the group of objects that mixed in Enumerable.
There, grep behaves like this (line by line):
x = "hello world baby girl"
x.grep(/hello/)
#=> ["hello world baby girl"]
x = "hello\nworld\nbaby\ngirl"
x.grep(/hello/)
#=> ["hello\n"]The same can be done in Ruby 1.9 by just splitting the String beforehand. Arrays are Enumerable and thus
still have grep:x = "hello\nworld\nbaby\ngirl"
x.split("\n").grep(/hello/)
#=> ["hello"]Note the absence of the line-break which might be intended or not :).
I would probably do this in 1.9:
string.lines.grep(/pattern/)
where lines returns an enumerator.
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
Not the same thing
using 1.9
irb(main):001:0> a = "abe\nbob\nfred\njim"
=> "abe\nbob\nfred\njim"
irb(main):002:0> a.scan(/b/)
=> ["b", "b", "b"]
irb(main):003:0> a.lines.grep(/b/)
=> ["abe\n", "bob\n"]
a.lines.grep does the same thing that a.grep would do in 1.8, a.scan does not.
On Sat, Nov 28, 2009 at 11:10 AM, Robert Klemme <shortcutter@googlemail.com> wrote:
On 11/28/2009 08:27 AM, David A. Black wrote:
Hi --
On Sat, 28 Nov 2009, Florian Gilcher wrote:
Grep is not defined on Ruby 1.9-Strings.
It was on Ruby 1.8-Strings, but only because they were belonging to the
group of objects that mixed in Enumerable.There, grep behaves like this (line by line):
x = "hello world baby girl"
x.grep(/hello/)
#=> ["hello world baby girl"]
x = "hello\nworld\nbaby\ngirl"
x.grep(/hello/)
#=> ["hello\n"]The same can be done in Ruby 1.9 by just splitting the String beforehand.
Arrays are Enumerable and thus
still have grep:x = "hello\nworld\nbaby\ngirl"
x.split("\n").grep(/hello/)
#=> ["hello"]Note the absence of the line-break which might be intended or not :).
I would probably do this in 1.9:
string.lines.grep(/pattern/)
where lines returns an enumerator.
Why not just string.scan(/pattern/) ?
--
Rick DeNatale
Blog: http://talklikeaduck.denhaven2.com/
Twitter: http://twitter.com/RickDeNatale
WWR: http://www.workingwithrails.com/person/9021-rick-denatale
LinkedIn: http://www.linkedin.com/in/rickdenatale
Stupid me, of course! Thanks for the quick enlightenment. I somehow had assumed the text the OP was ultimately interested in was that matched by the expression. But that assumption is not covered by the posting.
Cheers
robert
On 11/28/2009 05:35 PM, Rick DeNatale wrote:
On Sat, Nov 28, 2009 at 11:10 AM, Robert Klemme > <shortcutter@googlemail.com> wrote:
On 11/28/2009 08:27 AM, David A. Black wrote:
I would probably do this in 1.9:
string.lines.grep(/pattern/)
where lines returns an enumerator.
Why not just string.scan(/pattern/) ?
Not the same thing
using 1.9
irb(main):001:0> a = "abe\nbob\nfred\njim"
=> "abe\nbob\nfred\njim"
irb(main):002:0> a.scan(/b/)
=> ["b", "b", "b"]
irb(main):003:0> a.lines.grep(/b/)
=> ["abe\n", "bob\n"]a.lines.grep does the same thing that a.grep would do in 1.8, a.scan does not.
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/