mathx

README

mathx

Package mathx contains math utilities. It means to be a complement to the standard math package.

Documentation

Overview

Package mathx contains math utilities. It means to be a complement to the standard math package.

Index

• Constants
• func AbsInt(i int) int
• func Near(a, b, eps float64) bool
• func Round(x, unit float64) float64

Examples

• Round

Constants

const (
	MaxUint = ^uint(0)
	MinUint = 0
	MaxInt  = int(MaxUint >> 1)
	MinInt  = -MaxInt - 1
)

Compile time constants to determine the min and max values of the int and uint types.

Functions

func AbsInt

func AbsInt(i int) int

AbsInt returns the absolute value of i.

func Near

func Near(a, b, eps float64) bool

Near reports if 2 float64 numbers are "near" to each other. The caller is responsible to provide a sensible epsilon.

"near" is defined as the following:

near := math.Abs(a - b) < eps

Corner cases:

1. if a==b, result is true (eps will not be checked, may be NaN)
2. Inf is near to Inf (even if eps=NaN; consequence of 1.)
3. -Inf is near to -Inf (even if eps=NaN; consequence of 1.)
4. NaN is not near to anything (not even to NaN)
5. eps=Inf results in true (unless any of a or b is NaN)

func Round

func Round(x, unit float64) float64

Round returns x rounded to the given unit. Tip: x is "arbitrary", maybe greater than 1. For example:

Round(0.363636, 0.001) // 0.364
Round(0.363636, 0.01)  // 0.36
Round(0.363636, 0.1)   // 0.4
Round(0.363636, 0.05)  // 0.35
Round(3.2, 1)          // 3
Round(32, 5)           // 30
Round(33, 5)           // 35
Round(32, 10)          // 30

For details, see https://stackoverflow.com/a/39544897/1705598

Example

fmt.Printf("%.4f\n", Round(0.363636, 0.001)) // 0.364
fmt.Printf("%.4f\n", Round(0.363636, 0.01))  // 0.36
fmt.Printf("%.4f\n", Round(0.363636, 0.1))   // 0.4
fmt.Printf("%.4f\n", Round(0.363636, 0.05))  // 0.35
fmt.Printf("%.4f\n", Round(3.2, 1))          // 3
fmt.Printf("%.4f\n", Round(32, 5))           // 30
fmt.Printf("%.4f\n", Round(33, 5))           // 35
fmt.Printf("%.4f\n", Round(32, 10))          // 30

fmt.Printf("%.4f\n", Round(-0.363636, 0.001)) // -0.364
fmt.Printf("%.4f\n", Round(-0.363636, 0.01))  // -0.36
fmt.Printf("%.4f\n", Round(-0.363636, 0.1))   // -0.4
fmt.Printf("%.4f\n", Round(-0.363636, 0.05))  // -0.35
fmt.Printf("%.4f\n", Round(-3.2, 1))          // -3
fmt.Printf("%.4f\n", Round(-32, 5))           // -30
fmt.Printf("%.4f\n", Round(-33, 5))           // -35
fmt.Printf("%.4f\n", Round(-32, 10))          // -30

Output:

0.3640
0.3600
0.4000
0.3500
3.0000
30.0000
35.0000
30.0000
-0.3640
-0.3600
-0.4000
-0.3500
-3.0000
-30.0000
-35.0000
-30.0000