[ruby-talk:14182] Re: Ruby way to delete entries from an array

On Wed, 25 Apr 2001, Dave Thomas wrote:

> Jim Freeze <[e-mail]> writes:
>
> > I have an array where I need to delete several entries.
> > Here is how I am doing it.
> >
> > a = ["cat\n", "dog\n", "bird \n"]
> > rm = ["cat", "bird"]
> >
> > rm.each do |del|
> >   for i in (0...a.size).collect.reverse
> >     a.delete_at(i) if /#{del}/ =~ a[i]
> >   end
> > end
> >
> > Is there a more compact way to do this?
>
>
> Well, this is more compact. The fact that you're using regexp matches
> makes it a little tricky.
>
>  pattern = Regexp.new(rm.join('|'))
>  a.delete_if {|entry| entry =~ pattern }


Another possibility, for those who just can't get enough iteration:

  a.delete_if do |e|
    rm.detect do |r| /#{r}/.match(e) end
  end

>
> In the general case, where the elements of 'rm' might contain meta
> characters, you'd need the somewhat more cumbersome:
>
>  pattern = Regexp.new(rm.collect {|str| Regexp.escape(str) } .join('|'))

The equivalent for the above version (for completeness :-)

  a.delete_if do |e|
    rm.detect do |r| /#{Regexp.escape(r)}/.match e end
  end


David

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David Alan Black
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