Overview

In this tutorial we will study about

• % Operator – applicable to get remainder for integers

• Mod function – can be used to get remainder in case of floats also

• Remainder function – can be used to get IEEE 754 remainder

% Operator

Golang has a modulus operator (‘ %’), that can be used to get the remainder on dividing two integer numbers. Let’s see a working program illustrating this

Code

package main

import (
    "fmt"
)

func main() {
    res := 4 % 2
    fmt.Println(res)

    res = 5 % 2
    fmt.Println(res)

    res = 8 % 3
    fmt.Println(res)
}

Output:

0
1
2

Mod function for floats

% function doesn’t work for floats. For getting remainder when dividing two floats we can use the Mod function provided by the math package itself. Below is the signature of the function. It takes in two floats and returns a float. It will return floating point remainder of x/y. The output will take the sign on x

func Mod(x, y float64) float64

Some special cases of Mod function are

• Mod(±Inf, y) = NaN
• Mod(NaN, y) = NaN
• Mod(x, 0) = NaN
• Mod(x, ±Inf) = x
• Mod(x, NaN) = NaN

Code

package main

import (
    "fmt"
    "math"
)

func main() {
    res := math.Mod(4, 2)
    fmt.Println(res)

    res = math.Mod(4.2, 2)
    fmt.Println(res)

    res = math.Mod(5, 2)
    fmt.Println(res)

    res = math.Mod(-5, 2)
    fmt.Println(res)
}

Output

0
0.20000000000000018
1
-1

IEEE 754 Remainder

math package of GO provides a Remainder method that can be used to get IEEE 754 Remainder of two numbers, one acting as a Numerator and the acting as a denominator.

You can read more about why do we need IEEE 754 Remainder here – https://stackoverflow.com/questions/26671975/why-do-we-need-ieee-754-remainder

Below is the signature of the function. It takes input two numbers as float64 and returns a remainder which is also an IEEE 754 float64 Remainder.

func Remainder(x, y float64) float64

Some special cases of Remainder function are

• Remainder(±Inf, y) = NaN
• Remainder(NaN, y) = NaN
• Remainder(x, 0) = NaN
• Remainder(x, ±Inf) = x
• Remainder(x, NaN) = NaN

Code

package main

import (
    "fmt"
    "math"
)

func main() {
    res := math.Remainder(4, 2)
    fmt.Println(res)

    res = math.Remainder(5, 2)
    fmt.Println(res)

    res = math.Remainder(5.5, 2)
    fmt.Println(res)

    res = math.Remainder(5.5, 1.5)
    fmt.Println(res)
}

Output

0
1
-0.5
-0.5