Capitalize bug?

Hi!

I’m a new member here, though I use and enjoy ruby for about three
years. There’s a beginning to everyuthing, including thing not doing the
way you think they should, even in ruby!

So here’s my problem:

@nom = wnom.gsub(/_+(.)/, ‘\1’.upcase)

What this code should do is taking the string wnom, and removing every _
and at the same time capitalizing the letter immediatly after.

for instance do_it_now would become doItNow. One way to translate ruby
usage into camel case.

but this code does in fact producte doitnow instead of doItNow.

Now, I am not blocked, because I have achieved my goal with this code:

nom = wnom.gsub(/_+(.)/) { |deb| deb[1, 1].upcase }

but this is less clear, and surely less efficient (although this is not
a real problem in my case).

My question is WHY does my first code NOT do what I think it should?

Thank you for your help.


Jean-Pierre

On 11/14/06, Jean-pierre Riviere [email protected] wrote:

What this code should do is taking the string wnom, and removing every _

but this is less clear, and surely less efficient (although this is not
a real problem in my case).

My question is WHY does my first code NOT do what I think it should?

The problem is when the parameters are evaluated:

@nom = wnom.gsub(/_+(.)/, ‘\1’.upcase)

in this case, ‘\1’.upcase is evaluated BEFORE the gsub is called. As
‘\1’.upcase is equal to ‘\1’
what you’re doing is in fact:

@nom = wnom.gsub(/_+(.)/, ‘\1’)

in the block case, the block is evaluated AFTER the match is found and
therefore it works.

Jean-pierre Riviere wrote:

Hi!

I’m a new member here, though I use and enjoy ruby for about three
years. There’s a beginning to everyuthing, including thing not doing the
way you think they should, even in ruby!

So here’s my problem:

@nom = wnom.gsub(/_+(.)/, ‘\1’.upcase)

The parameters to gsub are: 1. a regex, 2. the result of ‘\1’.upcase
(that is, ‘\1’).

nom = wnom.gsub(/_+(.)/) { |deb| deb[1, 1].upcase }
If you want to substitute the substring with the result of applying a
function to it, your only choice is to use the block parameter to gsub,
yes. (Did the previous sentence parse?) Another possibility is to use
$1.upcase.

HTH

spooq wrote:

foo = “do_it_now”
foo.gsub(/_+(.)/, $1.upcase)
=> “doNtNow”

Inside the block…

foo = “do_it_now”
foo.gsub(/_+(.)/, $1.upcase)
=> “doNtNow”

On 11/14/06, Jean-pierre Riviere [email protected] wrote:

nom = wnom.gsub(/_+(.)/) { |deb| deb[1, 1].upcase }

This is clearer… the dollar vars are assigned properly inside the
block.

foo.gsub(/_+(.)/) { $1.upcase }

spooq wrote:

Now you tell me :wink:

Context is all :).

On 11/14/06, Carlos [email protected] wrote:

spooq wrote:

foo = “do_it_now”
foo.gsub(/_+(.)/, $1.upcase)
=> “doNtNow”

Inside the block…

Now you tell me :wink:

spooq wrote:

On 11/14/06, Jean-pierre Riviere [email protected] wrote:

nom = wnom.gsub(/_+(.)/) { |deb| deb[1, 1].upcase }

This is clearer… the dollar vars are assigned properly inside the
block.

foo.gsub(/_+(.)/) { $1.upcase }

thank you for all the explanations guys.

now, I don’t know which one is clearer… which one would you recommend?
Surely yours with $1 has a greater scope, especially if $1 recovered
something more complex in my regexp…

Just have to get used to it, I suppose.


Jean-Pierre

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