Substitution weirdness

ruby-talk
1

Hi,

Here’s some behaviour I don’t immediately understand:

irb(main):119:0> foo = “'123”
=> "‘123"
irb(main):120:0> foo.gsub(/’/, “\’”)
=> “123123”

Why does the apostrophe get replaced with a copy of the text that
follows it?

I’m trying to replace every instance of ’ with ’ but it’s proving very
tricky. Nothing I can come up with seems to work, no matter how many
backslashes I use, whether I use single or double quotes, whether or not
I use gsub with a block, etc.

This should be so easy, but it has me stumped.

Ian

···

–
Ian Macdonald | It is better to live rich than to die rich.
System Administrator | – Samuel Johnson
ian@caliban.org |
http://www.caliban.org |
>

2

Hi –

Hi,

Here’s some behaviour I don’t immediately understand:

irb(main):119:0> foo = “'123”
=> “'123”
irb(main):120:0> foo.gsub(/‘/, "\’")
=> “123123”

Why does the apostrophe get replaced with a copy of the text that
follows it?

What you’re hitting is a special meaning of ' – namely, the
post-match part of the match. It’s similar to the $`, $&, $’
variables (pre-match, match, post-match).

I’m trying to replace every instance of ’ with ' but it’s proving very
tricky. Nothing I can come up with seems to work, no matter how many
backslashes I use, whether I use single or double quotes, whether or not
I use gsub with a block, etc.

Try this:

“'123”.gsub(/‘/, "\\’")

David

···

On Fri, 30 May 2003, Ian Macdonald wrote:

–
David Alan Black
home: dblack@superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav

3
> irb(main):119:0> foo = "'123" > => "'123" > irb(main):120:0> foo.gsub(/'/, "\\'") > => "123123" > > Why does the apostrophe get replaced with a copy of the text that > follows it?

’ has special meaning (“after the match”, iirc, which makes sense here).
A string “” requires you to escape , as \, so:

“\’” => ’ => after-the-match substitution

Try:

foo.gsub /’/, “\\’” => “\'123”

(Remember that “\’” is ', because \ is escaped.) This double-escapes
the backslash for the results you want. (Try printing the result when
you get it.)

hth,

···

On Fri, 30 May 2003 06:58:35 +0900 Ian Macdonald ian@caliban.org wrote:

–
Ryan Pavlik rpav@users.sf.net

“Spinal hazards are hazardous…” - 8BT

4

foo = “'123”
puts foo.gsub(/‘/) {’\‘+"’"}

I find it more readable than the multiply-self-escaping string of
backslashes.

martin

···

Ian Macdonald ian@caliban.org wrote:

I’m trying to replace every instance of ’ with ' but it’s proving very
tricky. Nothing I can come up with seems to work, no matter how many
backslashes I use, whether I use single or double quotes, whether or not
I use gsub with a block, etc.

This should be so easy, but it has me stumped.

5

Thanks. I couldn’t see why ' might be getting expanded like that, as I
didn’t see it as being analogous to $’

This works for me, too, and is a little more readable to my eyes:

“'123”.gsub(/‘/) { %q(\’) }

Ian

···

On Fri 30 May 2003 at 07:04:35 +0900, dblack@superlink.net wrote:

On Fri, 30 May 2003, Ian Macdonald wrote:

Hi,

Here’s some behaviour I don’t immediately understand:

irb(main):119:0> foo = “'123”
=> “'123”
irb(main):120:0> foo.gsub(/‘/, "\’")
=> “123123”

Why does the apostrophe get replaced with a copy of the text that
follows it?

What you’re hitting is a special meaning of ' – namely, the
post-match part of the match. It’s similar to the $`, $&, $’
variables (pre-match, match, post-match).

I’m trying to replace every instance of ’ with ' but it’s proving very
tricky. Nothing I can come up with seems to work, no matter how many
backslashes I use, whether I use single or double quotes, whether or not
I use gsub with a block, etc.

Try this:

“'123”.gsub(/‘/, "\\’")

–
Ian Macdonald | If all the world’s economists were laid end
System Administrator | to end, we wouldn’t reach a conclusion.
ian@caliban.org | – William Baumol
http://www.caliban.org |
>

6

But ‘\’ and “\” are the same thing (a single backslash)

puts ‘\’.size #>> 1
puts “\”.size #>> 1

So concatenating two strings like that doesn’t help you at all.

Regards,

Brian.

···

On Fri, May 30, 2003 at 08:48:04PM +0900, Martin DeMello wrote:

Ian Macdonald ian@caliban.org wrote:

I’m trying to replace every instance of ’ with ' but it’s proving very
tricky. Nothing I can come up with seems to work, no matter how many
backslashes I use, whether I use single or double quotes, whether or not
I use gsub with a block, etc.

This should be so easy, but it has me stumped.

foo = “'123”
puts foo.gsub(/‘/) {’\‘+"’"}

I find it more readable than the multiply-self-escaping string of
backslashes.

7

Hi,

···

At Fri, 30 May 2003 07:10:13 +0900, Ian Macdonald wrote:

This works for me, too, and is a little more readable to my eyes:

“'123”.gsub(/‘/) { %q(\’) }

Or:

“'123”.gsub(/'/, ‘\&’)

–
Nobu Nakada

8

foo = “'123”
puts foo.gsub(/‘/) {’\‘+"’"}

I find it more readable than the multiply-self-escaping string of
backslashes.

But ‘\’ and “\” are the same thing (a single backslash)

Yeah, that was simply a matter of defaulting to ‘’ for constant strings
unless I need a “'”

So concatenating two strings like that doesn’t help you at all.

Oops - so it doesn’t. Please to ignore that post. What did help is that
“\'” doesn’t seem to be magic in the {} form of gsub.

martin

···

Brian Candler B.Candler@pobox.com wrote:

On Fri, May 30, 2003 at 08:48:04PM +0900, Martin DeMello wrote:

9

Hi,

···

At Fri, 30 May 2003 13:13:51 +0900, nobu.nokada@softhome.net wrote:

“'123”.gsub(/‘/) { %q(\’) }

Or:

“'123”.gsub(/'/, ‘\&’)

Sorry, too stupid. Ignore the previous post.

–
Nobu Nakada