# Golang : Arithmetic operation with numerical slices or arrays example

Got an email from a new comer to Golang from South Africa, he or she wanted to know how to perform simple operations like arithmetic on numerical slices. There is a package - GoNum - that can do a better job for these kind of problems ... which I reckon is more efficient for mathematical calculations than using Golang's standard slices. However, there is no harm to use slices if all you wanted is to perform some simple operations like plus, minus, multiplication or division on slices or array.

Below is an example of how to use slices for arithmetic operations:

`````` package main

import (
"fmt"
)

func main() {
a := []int{1, 2, 3, 4}

fmt.Println("Original : ", a)

// a * 2
for i, _ := range a {
a[i] = a[i] * 2
}

fmt.Println("a * 2 : ", a)

// a + 10
for i, _ := range a {
a[i] = a[i] + 10
}

fmt.Println("a + 10 : ", a)

b := []int{5, 6, 7, 8}

fmt.Println("b : ", b)

lengthOfA := len(a)

// will cause non-constant array bound lengthOfA error
//c := [lengthOfA]int{}

// if c size is constant, it is ok to hardcode with size of 4 (hand counted)
// c := int{}

// or to make your program more robust
// figure out the slice c's length during runtime with length of a slice
c := make([]int, lengthOfA)

// a + b
// FOR a slice to plus b slice, the size or number of elements in both slices must be the same!
for i, _ := range a {
c[i] = a[i] + b[i]
}

fmt.Printf("a + b : %v + %v = %v \n", a, b, c)

d := make([]int, lengthOfA)

// a * b
for i, _ := range a {
d[i] = a[i] * b[i]
}

fmt.Printf("a * b : %v * %v = %v \n", a, b, d)

// use float64 instead of int type for division
e := make([]float64, lengthOfA)

// a / b
for i, _ := range a {
e[i] = float64(a[i]) / float64(b[i])
}

fmt.Printf("a / b : %v * %v = %v \n", a, b, e)

f := make([]int, lengthOfA)

// a - b
for i, _ := range a {
f[i] = a[i] - b[i]
}

fmt.Printf("a - b : %v * %v = %v \n", a, b, f)
}
``````

Output:

Original : [1 2 3 4]

a * 2 : [2 4 6 8]

a + 10 : [12 14 16 18]

b : [5 6 7 8]

a + b : [12 14 16 18] + [5 6 7 8] = [17 20 23 26]

a * b : [12 14 16 18] * [5 6 7 8] = [60 84 112 144]

a / b : [12 14 16 18] * [5 6 7 8] = [2.4 2.3333333333333335 2.2857142857142856 2.25]

a - b : [12 14 16 18] * [5 6 7 8] = [7 8 9 10]

References:

https://socketloop.com/tutorials/golang-combine-slices-of-complex-numbers-and-operation-example

https://www.socketloop.com/tutorials/golang-squaring-elements-in-array

https://www.socketloop.com/tutorials/golang-automatically-figure-out-array-length-size-with-three-dots