Find matching elements in array

Ruby
1

Hi,
I have one array for example[1,2,3,4]

i need to find the matching elements of another array is there any way
to find…
for example [1,2,3,4].include?(2)
it will return true
but i need to find one or more elements
example : [1,2,3,4].include?(2,3)
it is throwing an error

If you have solution reply me

Thanx
Pragash

2

On Mon, Jul 7, 2008 at 4:04 PM, Pragash Mr.
[email protected] wrote:

I have one array for example[1,2,3,4]
i need to find the matching elements of another array is there any way
to find…
for example [1,2,3,4].include?(2)
it will return true
but i need to find one or more elements
example : [1,2,3,4].include?(2,3)
it is throwing an error

Depends what you want, if you just want to find out if the numbers 2
and 3 are in the other array, you could use:

== Array RDoc:
array & other_array
Set Intersection—Returns a new array containing elements common to
the two arrays, with no duplicates.
[ 1, 1, 3, 5 ] & [ 1, 2, 3 ] #=> [ 1, 3 ]

so you could do something like this:

class Array
def contains?(array)
(self & array) == array
end
end
=> nil

?> [1,2,3,4].contains?([1,2])
=> true
?> [1,2,3,4].contains?([1,3])
=> true

[1,2,3,4].contains?([1,9])
=> false
[1,2,3,4].contains?([12,3])
=> false
[1,2,3,4].contains?([2,3])
=> true

Mikel

3

class Array
def contains?(array)
(self & array) == array
end
end

Note however, this will only work if the match is in order.

For example

[1,2,3,4].contains?([2,1]) #=> false

But

[1,2,3,4].contains?([1,4]) #=> true

That might be what you want. If not, you could call sort on it as well.

ANyway… the point is, you can have a look at the ruby rdoc and find
a lot about this. Arrays have been around for a while and Ruby
handles them more elegantly than any other language I have used.

Go have a read: class Array - RDoc Documentation

Mikel

4

On 07.07.2008, at 08:04, Pragash Mr. wrote:

If you have solution reply me

class Array
alias old_include? include?
def include?(*args)

 if args.length <= 1
   old_include?(args)
 else
   args.all? do |a|
     old_include?(a)
   end
 end

end
end

puts("#{(0…9).to_a.include?(3,5)}") # true
puts("#{(‘a’…‘z’).to_a.include?(3,5)}") # false
puts("#{(‘A’…‘ZZ’).to_a.include?(‘G’,‘AB’)}")# true

regards, Sandor
Szücs

5

On Jul 7, 1:04 am, “Pragash Mr.” [email protected]
wrote:

If you have solution reply me

Thanx
Pragash

Posted viahttp://www.ruby-forum.com/.

How about something like this?

a = [1,2,3,4]
x = [2,3]

x.all? { |n| a.include?(n) }

(warning, this is slow for large arrays)

Jeff

6

On Jul 7, 1:32 am, Sandor Szücs [email protected] wrote:

 end

end
end

puts(“#{(0…9).to_a.include?(3,5)}”) # true
puts(“#{(‘a’…‘z’).to_a.include?(3,5)}”) # false
puts(“#{(‘A’…‘ZZ’).to_a.include?(‘G’,‘AB’)}”)# true

regards, Sandor Szücs

Two things:

  1. This doesn’t work. Try (‘a’…‘z’).to_a.include?(‘a’)
  2. The length check isn’t necessary. It’s sufficient to just use
    args.all? { |a| old_include?(a) }, assuming it’s okay that calling
    include? with no arguments now returns true.

I like Mikel’s set-intersection solution (which, incidentally, is what
I was thinking), assuming once again that the order is important.

7

Hi –

On Tue, 8 Jul 2008, Yossef M. wrote:

   args.all? do |a|

regards, Sandor Szücs

Two things:

  1. This doesn’t work. Try (‘a’…‘z’).to_a.include?(‘a’)
  2. The length check isn’t necessary. It’s sufficient to just use
    args.all? { |a| old_include?(a) }, assuming it’s okay that calling
    include? with no arguments now returns true.

I’d be in favor of keeping that safeguard, partly because it feels
weird for [1,2,3].include?() to be true and partly because there might
be some edge case or test where having it succeed silently might be
problematic.

A case statement might be a nice way to handle it:

def include?(*args)
case args.size
when 0
old_include?
else
args.all? {|a| old_include?(a) }
end
end

I also think this one is kind of cool, though I would assume it’s a
good bit slower:

def include?(head,*tail)
case tail
when []
old_include?(head)
else
include?(head) && include?(*tail)
end
end

David

8

On Jul 7, 9:12 pm, “David A. Black” [email protected] wrote:

On Tue, 8 Jul 2008, Yossef M. wrote:

  1. The length check isn’t necessary. It’s sufficient to just use
    args.all? { |a| old_include?(a) }, assuming it’s okay that calling
    include? with no arguments now returns true.

I’d be in favor of keeping that safeguard, partly because it feels
weird for [1,2,3].include?() to be true and partly because there might
be some edge case or test where having it succeed silently might be
problematic.

Oh, I’d probably put a safeguard in there, possibly a check on the
number of arguments so that [1,2,3].include?() still raises an
ArgumentError.

My comment about the length check not being necessary wasn’t a
judgement of how I would write it
as much as it was just saying that code doesn’t perform any useful
function in that context. Personally, I think [].all? shouldn’t be
true, but that debate has happened before.

9

Hi,

On 08.07.2008, at 02:24, Yossef M. wrote:

   end

Two things:

  1. This doesn’t work. Try (‘a’…‘z’).to_a.include?(‘a’)

ack.

  1. The length check isn’t necessary. It’s sufficient to just use
    args.all? { |a| old_include?(a) }, assuming it’s okay that calling
    include? with no arguments now returns true.

ack.

I like Mikel’s set-intersection solution (which, incidentally, is what
I was thinking), assuming once again that the order is important.

That’s also what I thought if I read that e-mail.

regards, Sandor
Szücs