Short Number Count

shortcount.go

package main

import (
	"fmt"
	"math"
	"strconv"
)

func Round(input float64, places int) (rounded float64) {
	if math.IsNaN(input) {
		return input
	}
	sign := 1.0
	if input < 0 {
		sign = -1
		input *= -1
	}
	precision := math.Pow(10, float64(places))
	digit := input * precision
	_, decimal := math.Modf(digit)

	if decimal >= 0.5 {
		rounded = math.Ceil(digit)
	} else {
		rounded = math.Floor(digit)
	}
	return rounded / precision * sign
}

func ShortCount(n float64) string {
	var s string
	prefix := []byte{'T', 'B', 'M', 'k'}
	powers := []float64{1e+12, 1e+09, 1e+06, 1000}
	for i := range prefix {
		limit := powers[i]
		if n > limit {
			n = Round(n/limit, 0)
			rounded := strconv.FormatFloat(n, 'f', -1, 64)
			prefixed := string(prefix[i])
			return fmt.Sprintf("%s%s", rounded, prefixed)
		}
		if i == len(prefix)-1 {
			n = Round(n, 0)
			return strconv.FormatFloat(n, 'f', -1, 64)
		}
	}
	return s
}

func main() {
	fmt.Println(ShortCount(30534533333443.023423))
	fmt.Println(ShortCount(3054533333443.023423))
	fmt.Println(ShortCount(305353333443.023423))
	fmt.Println(ShortCount(30534333443.023423))
	fmt.Println(ShortCount(3053534443.023423))
	fmt.Println(ShortCount(305334443.023423))
	fmt.Println(ShortCount(30533443.023423))
	fmt.Println(ShortCount(3033443.023423))
	fmt.Println(ShortCount(344443.023423))
	fmt.Println(ShortCount(34443.023423))
	fmt.Println(ShortCount(3043.023423))
	fmt.Println(ShortCount(30.023423))
}