How to assign elements of an array from another array using indexes in Scala/Java?

Question

I want to assign a part of an array to a part of another array in Scala. For example, I want to do the Scala or Java equivalent of the following Python code.

x[i:j] = y[k:l]

How can I do that in Scala or even Java?

Assume that not all Scala coders know python. Be more specific in your description. You may want to remove the python tag as well. This isn't a python question. — WillD
– WillD, Commented Feb 2, 2017 at 19:54

Marth · Accepted Answer · 2017-02-02 17:35:16Z

1

You can use a combination of .patch and .slice:

scala> val a = Array.range(1, 20)
a: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)

scala> val b = Array.range(30, 50)
b: Array[Int] = Array(30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49)

scala> a.patch(5, b.slice(5, 10), 5)
res5: Array[Int] = Array(1, 2, 3, 4, 5, 35, 36, 37, 38, 39, 11, 12, 13, 14, 15, 16, 17, 18, 19)

The parameters of .slice are:

the element to start from (i in your python exemple)
the array to insert (y[k:l], here using .slice to select from k to l)
the number of element to replace in the array (unclear about what happens in your exemple when i:j is smaller than k:l, but I would guess it would be j-i here)

answered Feb 2, 2017 at 17:35

Marth

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2 Comments

pythonic Over a year ago

Would this be as efficient as System.arraycopy?

kouty Over a year ago

the first index is not 0, so the 19 is the 18th index in your first array?

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