array in array, like include?

[Ben]

Is there a function to checking to see if the elements of one array
exist in another?

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

Thanks!
Ben

 

[Joel VanderWerf]

Is there a function to checking to see if the elements of one array
exist in another?

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

Thanks!
Ben

require 'set'

[1,4].to_set.subset?([1,2,3,4,5].to_set)

=> true

 

[Joe Cheng]

Is there a function to checking to see if the elements of one array
exist in another?

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

How about:
(a & b).length == b.length

 

[Joel VanderWerf]

Is there a function to checking to see if the elements of one array
exist in another?

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

How about:
(a & b).length == b.length

(a&[1,4,4]).length == [1,4,4].length
=> false

so it might or might not be ok...

 

[Charles Steinman]

Is there a function to checking to see if the elements of one array
exist in another?

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

How about:
(a & b).length == b.length

That should be

==code==
(a & B).length != 0
==endcode==

Because & gives an array of the common members. So if they have no
common members, it will return a zero-length array, and a
nonzero-length array otherwise.

 

[Charles Steinman]

Is there a function to checking to see if the elements of one array
exist in another?

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

How about:
(a & b).length == b.length

That should be

==code==
(a & B).length != 0
==endcode==

Because & gives an array of the common members. So if they have no
common members, it will return a zero-length array, and a
nonzero-length array otherwise.

Immediately realized that I completely misread the requirements. Sorry
for the incorrect correction. D'oh.

 

[Pete Elmore]

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

The to_set solution is probably better, but you could do something like
class Array
def subset(s)
!s.find { |el| !self.include? el }
end
end

irb(main):018:0> [1, 2, 3, 4].subset([1, 2])
=> true
irb(main):019:0> [1, 2, 3, 4].subset([1, :seventy_five])
=> false

 

[Charles Steinman]

a = [1,2,3,4,5]
b = [1,4]

a.include?(b) will only work if b is a string. I'd like to get a
true/false if b exists in a.

The to_set solution is probably better, but you could do something like
class Array
def subset(s)
!s.find { |el| !self.include? el }
end
end

irb(main):018:0> [1, 2, 3, 4].subset([1, 2])
=> true
irb(main):019:0> [1, 2, 3, 4].subset([1, :seventy_five])
=> false

I benchmarked, and to_set came out way slower:

to_set.subset? another.to_set
0m19.089s

!another.find {|member| !include?(member)}
0m2.628s

another.all? {|member| include? member} # my solution
0m2.493s

 

[why the lucky stiff]

Is there a function to checking to see if the elements of one array
exist in another?

a = [1,2,3,4,5]
b = [1,4]

Elsewhere...

a = [1,2,3,4,5]
b = [1,4]
(b-a).empty?

=> true

c = [6, 4]
(c-a).empty?

=> false

_why

 

[dave.burt]

a = [1,2,3,4,5]
b = [1,4]
b.all? {|x| a.include? x } #=> true