1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
#![warn(missing_docs)]
#![warn(rust_2018_idioms)]
#![deny(unsafe_code)]
const NUMBER: [&str; 20] = [
"zero",
"one",
"two",
"three",
"four",
"five",
"six",
"seven",
"eight",
"nine",
"ten",
"eleven",
"twelve",
"thirteen",
"fourteen",
"fifteen",
"sixteen",
"seventeen",
"eighteen",
"nineteen",
];
#[rustfmt::skip]
const TENS: [&str; 10] = [
"",
"",
"twenty",
"thirty",
"forty",
"fifty",
"sixty",
"seventy",
"eighty",
"ninety",
];
const MULTIPLIER: [&str; 9] = [
"",
"thousand",
"million",
"billion",
"trillion",
"quadrillion",
"quintillion",
"sextillion",
"septillion",
];
pub trait Cardinal {
fn cardinal(&self) -> String;
}
macro_rules! impl_numeral_signed {
($($numtype:ty),*) => {$(
impl Cardinal for $numtype {
fn cardinal(&self) -> String {
cardinal_int(i64::from(*self).abs() as u64, self.is_negative())
}
}
)*};
}
impl_numeral_signed!(i8, i16, i32);
macro_rules! impl_numeral_unsigned {
($($numtype:ty),*) => {$(
impl Cardinal for $numtype {
fn cardinal(&self) -> String {
cardinal_int(u64::from(*self), false)
}
}
)*};
}
impl_numeral_unsigned!(u8, u16, u32, u64);
impl Cardinal for i64 {
fn cardinal(&self) -> String {
let n_abs = if *self == i64::MIN { *self as u64 } else { self.abs() as u64 };
cardinal_int(n_abs, self.is_negative())
}
}
impl Cardinal for isize {
fn cardinal(&self) -> String {
let n_abs = if *self == isize::MIN { *self as usize } else { self.abs() as usize };
cardinal_int(n_abs as u64, self.is_negative())
}
}
impl Cardinal for usize {
fn cardinal(&self) -> String {
cardinal_int(*self as u64, false)
}
}
fn cardinal_int(n: u64, negative: bool) -> String {
if n == 0 {
return String::from(NUMBER[0]);
}
let multiple_order = ((n as f32).log10() as u32) / 3;
let max_len = multiple_order as usize * 8 + 6;
let mut cardinal = Vec::with_capacity(max_len);
if negative {
cardinal.push("minus ");
}
compose_cardinal_int(n, multiple_order, &mut cardinal);
debug_assert!(cardinal.len() <= max_len);
cardinal.concat()
}
macro_rules! push {
($vec:ident, $table:ident[$index:ident]) => {
debug_assert!(
($index as usize) < $table.len(),
"{} out of {}'s range", stringify!($index), stringify!($table)
);
$vec.push($table[$index as usize]);
};
}
fn compose_cardinal_int(mut n: u64, mut multiple_order: u32, cardinal: &mut Vec<&str>) {
debug_assert_ne!(n, 0, "n == 0 in compose_cardinal_int()");
debug_assert_eq!(
multiple_order,
((n as f32).log10() as u32) / 3,
"wrong value for multiple_order in compose_cardinal_int()"
);
if multiple_order > 0 {
let mut multiplier = 10u64.pow(multiple_order * 3);
let mut multiplicand;
loop {
multiplicand = n / multiplier;
n %= multiplier;
if multiplicand != 0 {
push_triplet(multiplicand, cardinal);
cardinal.push(" ");
push!(cardinal, MULTIPLIER[multiple_order]);
if n != 0 {
cardinal.push(" ");
} else {
return;
}
}
multiple_order -= 1;
if multiple_order == 0 {
break;
}
multiplier /= 1000;
}
}
push_triplet(n, cardinal);
}
fn push_triplet(n: u64, cardinal: &mut Vec<&str>) {
debug_assert_ne!(n, 0, "n == 0 in push_triplet()");
debug_assert!(n < 1000, "n >= 1000 in push_triplet()");
let hundreds = n / 100;
let rest = n % 100;
if hundreds != 0 {
push!(cardinal, NUMBER[hundreds]);
if rest == 0 {
cardinal.push(" hundred");
return;
} else {
cardinal.push(" hundred ");
}
}
push_doublet(rest, cardinal);
}
fn push_doublet(n: u64, cardinal: &mut Vec<&str>) {
debug_assert_ne!(n, 0, "n == 0 in push_doublet()");
debug_assert!(n < 100, "n >= 100 in push_doublet()");
if n < 20 {
push!(cardinal, NUMBER[n]);
} else {
let tens = n / 10;
let ones = n % 10;
push!(cardinal, TENS[tens]);
if ones != 0 {
cardinal.push("-");
push!(cardinal, NUMBER[ones]);
}
}
}