Math

Languages often have built-in math methods. With Go we import the math module. This provides commonly-used methods like Abs and Pow.

Math methods here operate on the float64 numeric type. So we cannot use an int directly with them—we must cast it first. This requires some extra complexity.

Math.Abs

Let us begin with Abs. We import the math module in the import-statement at the top. Next we introduce the "negative" integer.

package main

import (
    "fmt"
    "math"
)

func main() {
    negative := -10
    fmt.Println(negative)
    // Use math.Abs to convert to a positive number.
    // ... We first convert to a float64.
    result := math.Abs(float64(negative))
    fmt.Println(result)
}
-10
10

Pow, compute exponents

Pow raises one number to another. Here we compute the cube of 2, which is 8. We can also square numbers (with a second argument of 2) or use higher powers.

package main

import (
    "fmt"
    "math"
)

func main() {
    // This can handle ints.
    result := math.Pow(2, 3)
    fmt.Println(result)
}
8

Max, Min

The math.Max and math.Min methods both receive two float64 values. Max returns the higher of the two. Min returns the lower.

package main

import (
    "fmt"
    "math"
)

func main() {
    small := float64(3)
    large := float64(40)

    // Get the larger of the two numbers.
    max := math.Max(small, large)
    fmt.Println(max)

    // Get the smaller value.
    min := math.Min(small, large)
    fmt.Println(min)
}
40
3

Floor

The floor is beneath us. With math.Floor, a number with a fractional part is always reduced so the fractional part does not exist. Both negative and positive numbers are reduced.

package main

import (
    "fmt"
    "math"
)

func main() {
    value1 := 1.23
    fmt.Println(value1)
    fmt.Println(math.Floor(value1))

    value2 := 2.99
    fmt.Println(value2)
    fmt.Println(math.Floor(value2))

    value3 := -1.1
    fmt.Println(value3)
    fmt.Println(math.Floor(value3))
}
1.23
1
2.99
2
-1.1
-2

Signbit

This math method returns a bool. If the number is negative (has a sign bit) then Signbit returns true. For positive numbers, it returns false.

package main

import (
    "fmt"
    "math"
)

func main() {
    value1 := float64(1)
    negative := math.Signbit(value1)
    fmt.Println(negative)

    value2 := float64(-1)
    negative = math.Signbit(value2)
    fmt.Println(negative)

    value3 := float64(0)
    negative = math.Signbit(value3)
    fmt.Println(negative)
}
false
true
false

Odd, even

An int has a parity: this is whether it is odd or even. To compute parity, we use a modulo division. We can define "odd" as "not even."

Fibonacci

In the Fibonacci sequence, each number is equal to the preceding two numbers. This sequence occurs often in the natural world. It has many uses.

Summary

Many math methods are available in the math package. We can implement math methods directly, with imperative statements. But this often leads to unneeded complexity.