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

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?

From: Frisco Del R. [mailto:[email protected]]

“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 :slight_smile:

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

On Apr 24, 10:04 am, Frisco Del R. [email protected] 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.

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. :slight_smile:

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

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