Slicing array in Ruby

Question

for slicing an array, we can use

 2.0.0p247 :021 > arr = [1,2,3,4,5] 
 => [1, 2, 3, 4, 5] 
2.0.0p247 :022 > arr.each_slice(3).to_a
 => [[1, 2, 3], [4, 5]] 
2.0.0p247 :034 > arr  # does not change array
 => [1, 2, 3, 4, 5]

i want to take only first part of sliced array, so i did it in the following way

2.0.0p247 :029 > arr = [1,2,3,4,5]
 => [1, 2, 3, 4, 5] 
2.0.0p247 :030 > arr[0..2]
 => [1, 2, 3] 
2.0.0p247 :031 > arr # does not change array
 => [1, 2, 3, 4, 5]

but it return a new array, and i want to do it in such a way that i can take a part of array in the same array without creating a new array As in Ruby there are some methods of changing same array by putting a '!' sign as - sort!,reject! etc

Is there any method of doing this?

when slicing, a new object is created anyway; just test with repeated arr[0..2].object_id in irb, for example. You might as well make it readable, so I'd go with Amy Hua's arr = arr.first 3 — icy
– icy, Commented Aug 9, 2013 at 20:31

Amy.js · Accepted Answer · 2013-08-08 21:58:33Z

5

Given

array = [1,2,3,4,5]

To return array=[1,2,3], you can:

Slice! off the last half, so you return the first half.
```
array.slice!(3..5)
```
Return the first three elements and assign it to the variable.
```
array = array.first 3
```
Or
```
array = array[0..2]
```

...Or use a number of other array methods.

answered Aug 8, 2013 at 21:58

Amy.js

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Cadoiz · Accepted Answer · 2022-11-28 05:53:26Z

2

Do you mean slice! as found in the ruby docs?:

1.9.3p392 :001 >     ar = [1,2,3,4,5]
=> [1, 2, 3, 4, 5]
1.9.3p392 :002 >     ar.slice!(0,2)
=> [1, 2]
1.9.3p392 :003 > ar
=> [3, 4, 5]

edited Nov 28, 2022 at 5:53

Cadoiz

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answered Aug 8, 2013 at 21:41

Rob Di Marco

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1 Comment

Ashish Kumar Over a year ago

nice, but i want to take only starting part to remain in the array.so i can do it as arr.slice!(2,arr.length-1)

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