Is it possible to initialize slice with specific values?

Question

Is it possible to initialize an slice with all 1's like in python?

PYTHON:

onesArray = np.ones(5)
onesList = [1]*5

GOLANG

onesSlice := make([]int, 5)
for i:= 0; i < len(onesSlice); i++{
    onesSlice[i] = 1
}

Is it possible to do better than this?

Performative

Answer 1

Yes but you have to use a different syntax.

oneSlice := []int{1, 1, 1, 1, 1}

It's referred to as 'composite literal'

Also, if there is reason to iterate (like calculating the values based loop variable or something) then you could use the range keyword rather than the old school for i is equal to, i is less than, i++ loop.

for i := range onesSlice {
    onesSlice[i] = 1
}

Almira

len(oneSlice) == cap(oneSlice) – Ruhnke

I want to create a slice containing n copies of integer val. Is there an easier way than looping? For example, in C++ I can do vector<int> a(n, val). – Clay

There is no easy way in Go as of 1.16. It would be nice if you could write eg make_init([]int, N, INIT_VAL) could create a slice of N times INIT_VAL (with capacity N). – Diggins

Answer 2

Starting with Go 1.23 which will be released in August 2024, there will be a special function Repeat() in the slices package, so the code would be like this:

onesArray := slices.Repeat([]int{1}, 5)

This code will solve the problem according to Adam Jones' proposal which was accepted a month ago.

Sam