Array problem

Ruby
1

I have an array like this:
array = [ “manyThings.mp3”, “myLike.gif”, “moreCoco.bmp”,
“theFormat.bmp”]

and I want to make some comparison to eliminate all the words in the
array that are NOT of the bmp format. So at the end the array will look
like this:

array = [“moreCoco.bmp”, “theFormat.bmp”]

is there a way to do this???

Many thanks for the help

2

John Zoldiark wrote:

I have an array like this:
array = [ “manyThings.mp3”, “myLike.gif”, “moreCoco.bmp”,
“theFormat.bmp”]

and I want to make some comparison to eliminate all the words in the
array that are NOT of the bmp format. So at the end the array will look
like this:

array = [“moreCoco.bmp”, “theFormat.bmp”]

is there a way to do this???

Many thanks for the help

Hi John,
Yep, try this:

array.reject! {|elem| elem.split(".").last != “bmp”}

Cheers,
Sebastian

3

And just another note: generally, for transforming and/or iterating over
arrays, finding/removing elements, extracting values, and so on, you’ll
want to take a look at Ruby’s “Enumerable” module. It’s available on all
the main collections in Ruby and is extremely handy.

Particularly, the “each”, “select”, “map”, “partition” and “reject”
methods are very handy. I use “map” and “select” all the time.

4

I think this should do it:

array.delete_if { |elem| not elem =~ /.bmp/i }
It worked for the following test:
array = [ “manyThings.mp3”, “myLike.gif”, “moreCoco.BmP”,
“theFormat.bmp”]
array.delete_if { |elem| not elem =~ /.bmp/i }
array.each do |elem|
puts elem
end

5

See Array#select
irb(main):007:0> array.select{|x| x.match(/.*.bmp/)}
=> [“moreCoco.bmp”, “theFormat.bmp”]

6

you might also want to anchor your regex
(the $ at the end) so that it won’t work on
file names like ‘foo.bmp.gz’. and be sure
to escape your . in front of bmp with .

array.delete_if { |elem| elem !~ /.bmp$/i }

also note the regex not match operator !~

cheers,
_c

7

Actually, the regex should have the end of string anchor:
array.delete_if { |elem| not elem =~ /.bmp$/i }

8

Joshua B. wrote:

Actually,  the regex should have the end of string anchor:
array.delete_if { |elem| not elem =~ /.bmp$/i }

Also, remember that . is any character, whereas . is just . for the
sake of getting exactly what you want. !~ looks cleaner to me, but
that’s just personal preference in most cases.

9

Arg… regex…I am new to them. :wink: You are right, of course.
Thanks (for the correction and the !~)

10

if you are like me an ignorant of regex, you could try this

array.delete_if { |elem| elem.index_of(".bmp") + 4 = elem.size}
though I don’t have an interpreter at the moment, so it hasn’t been
tested…

11

This works fine:

array.select { |item| item =~ /.bmp/ }

– Josh
http://iammrjoshua.com

Pierre P. wrote:

if you are like me an ignorant of regex, you could try this

array.delete_if { |elem| elem.index_of(“.bmp”) + 4 = elem.size}
though I don’t have an interpreter at the moment, so it hasn’t been
tested…

12

array.grep /bmp$/
=> [“moreCoco.bmp”, “theFormat.bmp”]

13

John Zoldiark wrote:

I have an array like this:
array = [ “manyThings.mp3”, “myLike.gif”, “moreCoco.bmp”,
“theFormat.bmp”]

and I want to make some comparison to eliminate all the words in the
array that are NOT of the bmp format. So at the end the array will look
like this:

array = [“moreCoco.bmp”, “theFormat.bmp”]

Instead of a reject/select you can also use grep when working with
regexen:
array.grep(/.bmp$/)
Instead of using a regex you could also use File.extname here:
array.select {|x| File.extname(x)==".bmp"}
Of course all these only tell you that the filenames end with .bmp, not
in
which format the files actually are.

HTH,
Sebastian