# Question about array.each{|x| delete x}

**URL:** <https://www.ruby-forum.com/t/question-about-array-each-x-delete-x/135701>\
**Category:** Ruby\
**Created:** [April 24, 2008, 11:11am UTC](https://www.ruby-forum.com/t/question-about-array-each-x-delete-x/135701 "2008-04-24T11:11:16Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Frisco\_Del\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/eb9ed0/32.png) [@Frisco\_Del\_R](https://www.ruby-forum.com/u/Frisco_Del_R)\
**Post date:** [April 24, 2008, 11:11am UTC](https://www.ruby-forum.com/t/question-about-array-each-x-delete-x/135701/1 "2008-04-24T11:11:16Z")

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myArray = [1, 2, 3]

puts myArray

myArray.each {|x|  
if x == 1  
then puts “one”  
elsif x == 2  
then  
myArray.delete x  
elsif x == 3  
then puts “three”  
end  
}

puts myArray

The output of the above is:  
1  
2  
3  
one  
1  
3

And my question is “why isn’t it 1 2 3 one three 1 3?”. What if I wanted  
to make it so?

---

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**Author:** ![Frisco\_Del\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/eb9ed0/32.png) [@Frisco\_Del\_R](https://www.ruby-forum.com/u/Frisco_Del_R)\
**Post date:** [April 24, 2008, 11:57am UTC](https://www.ruby-forum.com/t/question-about-array-each-x-delete-x/135701/2 "2008-04-24T11:57:26Z")

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From: Frisco Del R. [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]

# “why isn’t it 1 2 3 one three 1 3?”.

a delete (of some element) on an array will really be deleted, ergo, the  
elements will rearrange/move to logically occupy that deleted space.

eg,  
b=[1,2,3,4,5]  
#=\> [1, 2, 3, 4, 5]  
b.delete 2  
#=\> 2  
b  
#=\> [1, 3, 4, 5]

also, array#delete(obj) will delete all elements eql to obj. see below.  
now, if you combine these behaviours while walking the array itself,  
expect some surprises if you’re not ready 🙂

maybe if you show the index, ruby can help you, eg

a=[1,2,3,1,1,4]  
#=\> [1, 2, 3, 1, 1, 4]  
a.each\_with\_index{|x,i| a.delete x if x==1; puts “#{i} → #{x}”}  
0 → 1  
1 → 3  
2 → 4  
#=\> [2, 3, 4]

# What if I wanted to make it so?

there are many better ways, but i will just modify your sample,

myArray = [1, 2, 3]  
puts myArray  
myArray.delete 2 #here i delete 2 first  
myArray.each {|x|  
if x == 1  
then puts “one”  
elsif x == 3  
then puts “three”  
end  
}  
puts myArray

1  
2  
3  
one  
three  
1  
3

kind regards -botp

---

<div class="post-metadata">

**Author:** ![Frisco\_Del\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/eb9ed0/32.png) [@Frisco\_Del\_R](https://www.ruby-forum.com/u/Frisco_Del_R)\
**Post date:** [April 24, 2008, 1:11pm UTC](https://www.ruby-forum.com/t/question-about-array-each-x-delete-x/135701/3 "2008-04-24T13:11:48Z")

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On Apr 24, 10:04 am, Frisco Del R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> elsif x == 3  
> one  
> 1  
> 3
> 
> And my question is “why isn’t it 1 2 3 one three 1 3?”. What if I wanted  
> to make it so?

I just dup, like this:  
myArray.dup.each {|x| … delete from (original) myArray in  
here … }

I’m sure there are more elegant solutions, and it’s a bit pants from a  
performance perspective for large arrays, but it works for me.

---

<div class="post-metadata">

**Author:** ![Frisco\_Del\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/eb9ed0/32.png) [@Frisco\_Del\_R](https://www.ruby-forum.com/u/Frisco_Del_R)\
**Post date:** [April 24, 2008, 11:21pm UTC](https://www.ruby-forum.com/t/question-about-array-each-x-delete-x/135701/4 "2008-04-24T23:21:01Z")

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On 24.04.2008 11:56, Peña wrote:

> b  
> 0 -\> 1  
> puts myArray  
> 1  
> 2  
> 3  
> one  
> three  
> 1  
> 3
> 
> kind regards -botp

Well, you can as well do

myArray = [1, 2, 3]

puts myArray

myArray.delete\_if {|x|  
if x == 1 then  
puts “one”  
elsif x == 2 then  
true  
elsif x == 3 then  
puts “three”  
end  
}

puts myArray

Note, this works because puts returns nil. 🙂

But I’d prefer using case

myArray.delete\_if do |x|  
case x  
when 1  
puts “one”  
when 2  
true  
when 3  
puts “three”  
end  
end

Cheers

robert