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shortscale.go
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shortscale.go
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package shortscale
import (
"strings"
)
// Shortscale converts numbers into English words.
// Supports positive integers from 0 to 999_999_999_999_999_999.
// Larger values return "(big number)".
func Shortscale(n uint64) string {
if n <= 20 {
return numwords[n]
}
if n > 999_999_999_999_999_999 {
return "(big number)"
}
b := new(strings.Builder)
writeScale(b, n, 1_000_000_000_000_000) // quadrillions
writeScale(b, n, 1_000_000_000_000) // trillions
writeScale(b, n, 1_000_000_000) // billions
writeScale(b, n, 1_000_000) // millions
writeScale(b, n, 1_000) // thousands
writeHundreds(b, n)
writeTensAndUnits(b, n, b.Len() > 0)
return b.String()
}
func writeTensAndUnits(b *strings.Builder, n uint64, ifAnd bool) {
n = n % 100
if n == 0 {
return
}
if ifAnd {
writeWord(b, "and")
}
if n <= 20 {
writeWord(b, numwords[n])
return
}
writeWord(b, numwords[n/10*10]) // tens
units := n % 10
if units > 0 {
writeWord(b, numwords[units])
}
}
func writeHundreds(b *strings.Builder, n uint64) {
n = n / 100 % 10
if n == 0 {
return
}
writeWord(b, numwords[n])
writeWord(b, numwords[100])
}
func writeScale(b *strings.Builder, n uint64, thousands uint64) {
n = n / thousands % 1_000
if n == 0 {
return
}
writeHundreds(b, n)
writeTensAndUnits(b, n, (n/100%10) > 0)
writeWord(b, numwords[thousands])
}
func writeWord(b *strings.Builder, word string) {
if b.Len() > 0 {
b.WriteString(" ")
}
b.WriteString(word)
}
var numwords = map[uint64]string{
0: "zero",
1: "one",
2: "two",
3: "three",
4: "four",
5: "five",
6: "six",
7: "seven",
8: "eight",
9: "nine",
10: "ten",
11: "eleven",
12: "twelve",
13: "thirteen",
14: "fourteen",
15: "fifteen",
16: "sixteen",
17: "seventeen",
18: "eighteen",
19: "nineteen",
20: "twenty",
30: "thirty",
40: "forty",
50: "fifty",
60: "sixty",
70: "seventy",
80: "eighty",
90: "ninety",
100: "hundred",
1_000: "thousand",
1_000_000: "million",
1_000_000_000: "billion",
1_000_000_000_000: "trillion",
1_000_000_000_000_000: "quadrillion",
}