How to mimic Perl's `s///' in Ruby?

[Jos Backus]

Given Perl's

$_ = "123 foo";

s/^(\d+)\s+//;
$pid = $1;

print "$_\n$pid\n";

all I can come up with is

line = "123 foo"

pid = nil
line.sub!(/^(\d+)\s+/) {pid = $1; ''}

puts line, pid

Is there a better way perhaps?

--
Jos Backus _/ _/_/_/ Sunnyvale, CA
_/ _/ _/
_/ _/_/_/
_/ _/ _/ _/
jos at catnook.com _/_/ _/_/_/ require 'std/disclaimer'

 

[James Edward Gray II]

Given Perl's

$_ = "123 foo";

s/^(\d+)\s+//;
$pid = $1;

print "$_\n$pid\n";

all I can come up with is

line = "123 foo"

pid = nil
line.sub!(/^(\d+)\s+/) {pid = $1; ''}

puts line, pid

Is there a better way perhaps?

I don't think I understand the question. Ruby supports replacement
with and empty string and even $1, just like Perl.

line.sub!(/^((\d+)\s+/, "")
puts "#{line}\n#{$1}"

Hope that helps.

James Edward Gray II

 

[Daniel Berger]

Given Perl's

$_ = "123 foo";

s/^(\d+)\s+//;
$pid = $1;

print "$_\n$pid\n";

all I can come up with is

line = "123 foo"

pid = nil
line.sub!(/^(\d+)\s+/) {pid = $1; ''}

puts line, pid

Is there a better way perhaps?

Use split over a regex when you can:

pid, line = "123 foo".split

puts pid
puts line

Also keep in mind that 'pid' is currently still a string, not a number
(if that matters to you).

Regards,

Dan

 

[Glenn Parker]

Given Perl's

$_ = "123 foo";

s/^(\d+)\s+//;
$pid = $1;

print "$_\n$pid\n";

all I can come up with is

line = "123 foo"

pid = nil
line.sub!(/^(\d+)\s+/) {pid = $1; ''}

puts line, pid

Closer to the original Perl:

line = "123 foo"
line.sub!(/^(\d+)\s+/, '')
pid = $1
puts line, pid

The Pickaxe doc for String#sub states the MatchData $-variables will be
available using the block form of String#sub!, but it doesn't bother to
remind you that they are available in the non-block form as well.

 

[Thomas E Enebo]

Closer to the original Perl:

line = "123 foo"
line.sub!(/^(\d+)\s+/, '')
pid = $1
puts line, pid

Even a little closer to the original perl...Though I am sure you are
not asking how to get ruby syntax closer to Perls

alias :s :sub

$_ = "123 foo";

s /^(\d+)\s+/, '';
$pid = $1;

print "#$_\n#$pid\n";

-Tom

 

[Florian Gross]

Closer to the original Perl:

line = "123 foo"
line.sub!(/^(\d+)\s+/, '')
pid = $1
puts line, pid

line = "123 foo"
pid = line.slice!(/\d+/, 1).to_i
puts line, pid

..slice!() is the in-place version of [] that will delete the matched
stuff as well as returning it. Note that you can use Regexps with [] and
even []=.

str = "hello world"
str[/.(.)/, 1] # => "e"
str[/\s(.+)/, 1] = "bar"
str # => "hello bar"

 

[Jos Backus]

The Pickaxe doc for String#sub states the MatchData $-variables will be
available using the block form of String#sub!, but it doesn't bother to
remind you that they are available in the non-block form as well.

Duh, for some reason I didn't realize that $1 etc. are available _outside_ the
block in the first place as they are global.

Thanks for all your responses people, enlightening as always.

--
Jos Backus _/ _/_/_/ Sunnyvale, CA
_/ _/ _/
_/ _/_/_/
_/ _/ _/ _/
jos at catnook.com _/_/ _/_/_/ require 'std/disclaimer'

 

[Jos Backus]

I don't think I understand the question. Ruby supports replacement
with and empty string and even $1, just like Perl.

Somehow I didn't realize the significance of the $ in $1.

line.sub!(/^((\d+)\s+/, "")
puts "#{line}\n#{$1}"

Hope that helps.

Sure does, thanks.

--
Jos Backus _/ _/_/_/ Sunnyvale, CA
_/ _/ _/
_/ _/_/_/
_/ _/ _/ _/
jos at catnook.com _/_/ _/_/_/ require 'std/disclaimer'

 

[Jos Backus]

On Thu, Feb 10, 2005 at 06:25:06AM +0900, Florian Gross wrote:
[snip]

str = "hello world"
str[/.(.)/, 1] # => "e"
str[/\s(.+)/, 1] = "bar"
str # => "hello bar"

and

$1 # => "world"

Isn't it too bad a non-match raises an IndexError instead of returning nil?

irb(main):006:0> if str[/(hello)/, 1] = ""; puts "match", $1; end
match
hello
=> nil
irb(main):007:0> if str[/(hallo)/, 1] = ""; puts "match", $1; end
IndexError: regexp not matched
from (irb):7:in `[]='
from (irb):7
irb(main):008:0>

--
Jos Backus _/ _/_/_/ Sunnyvale, CA
_/ _/ _/
_/ _/_/_/
_/ _/ _/ _/
jos at catnook.com _/_/ _/_/_/ require 'std/disclaimer'

 

[Robert Klemme]

Given Perl's

$_ = "123 foo";

s/^(\d+)\s+//;
$pid = $1;

print "$_\n$pid\n";

all I can come up with is

line = "123 foo"

pid = nil
line.sub!(/^(\d+)\s+/) {pid = $1; ''}

puts line, pid

Is there a better way perhaps?

Others have shown ways to mimic Perl - even so far as to include the
trailing semicolons. I don't know why you want to mimic Perl, but here's
how I'd do it in Ruby:

if /^(\d+)\s+(.*)$/ =~ str
pid, name = $1, $2
else
# no match
end

Or, if you expect it to always match:

raise "String error: #{str}" unless /^(\d+)\s+(.*)$/ =~ str
pid, name = $1, $2

Kind regards

robert

 

[Wybo Dekker]

Given Perl's

$_ = "123 foo";

s/^(\d+)\s+//;
$pid = $1;

print "$_\n$pid\n";

all I can come up with is

line = "123 foo"

pid = nil
line.sub!(/^(\d+)\s+/) {pid = $1; ''}

puts line, pid

Is there a better way perhaps?

irb(main):001:0> $_='123 foo'
=> "123 foo"
irb(main):002:0> puts (sub(/(\d+)\s*/,'')),$1
foo
123
=> nil

 

[Assaph Mehr]

raise "String error: #{str}" unless /^(\d+)\s+(.*)$/ =~ str
pid, name = $1, $2

One thing I've wondered about: is this thread safe? Is there a chance
that between the first and second statements something will change the
result of the global variables?

I tend to use the more verbose:
.. pid, name = str.match(/^(\d+)\s+(.*)$/).captures
or
.. pid, name = str.scan(/^(\d+)\s+(.*)$/).flatten

Cheers,
Assaph

 

[Florian Gross]

Isn't it too bad a non-match raises an IndexError instead of returning nil?

irb(main):006:0> if str[/(hello)/, 1] = ""; puts "match", $1; end
match
hello
=> nil
irb(main):007:0> if str[/(hallo)/, 1] = ""; puts "match", $1; end
IndexError: regexp not matched
from (irb):7:in `[]='
from (irb):7
irb(main):008:0>

Not sure why you'd want to do that (.slice!() works better IMHO), but
perhaps you can do it like this:

"hello"[/((?:hallo)?)/, 1] = ""

 

[Florian Gross]

One thing I've wondered about: is this thread safe? Is there a chance
that between the first and second statements something will change the
result of the global variables?

They are thread-global variables. The same applies for $_.

I still prefer this form for complex matches, though:

if md = re.match(str) then
capture1, capture2 = md.captures
...
end

 

[Assaph Mehr]

They are thread-global variables. The same applies for $_.

I still prefer this form for complex matches, though:

if md = re.match(str) then
capture1, capture2 = md.captures
...
end

Nice, thanks.

 

[Glenn Parker]

Duh, for some reason I didn't realize that $1 etc. are available _outside_ the
block in the first place as they are global.

Not truly global, but per-thread instead.

 

[Jos Backus]

Jos Backus wrote:
Not sure why you'd want to do that (.slice!() works better IMHO), but
perhaps you can do it like this:

"hello"[/((?:hallo)?)/, 1] = ""

Yes, that works too. And I just tried the slice! version and it is more
elegant than the [] solution. Thanks Florian.

--
Jos Backus _/ _/_/_/ Sunnyvale, CA
_/ _/ _/
_/ _/_/_/
_/ _/ _/ _/
jos at catnook.com _/_/ _/_/_/ require 'std/disclaimer'

 

[Jos Backus]

Not truly global, but per-thread instead.

Oops, you're right. Thanks Glenn.

--
Jos Backus _/ _/_/_/ Sunnyvale, CA
_/ _/ _/
_/ _/_/_/
_/ _/ _/ _/
jos at catnook.com _/_/ _/_/_/ require 'std/disclaimer'