95 lines
3.1 KiB
Rust
95 lines
3.1 KiB
Rust
/*
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* MIT License
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*
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* Copyright (c) 2026 YuYuKunKun
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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/// 将 f64 格式化为与 Python `:g` (6 位有效数字) 兼容的字符串。
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pub fn format_f64_g(value: f64) -> String {
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if value.is_nan() {
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return "nan".to_string();
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}
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if value.is_infinite() {
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return if value > 0.0 {
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"inf".to_string()
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} else {
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"-inf".to_string()
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};
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}
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if value == 0.0 {
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return "0".to_string();
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}
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let abs = value.abs();
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let exp = abs.log10().floor() as i32;
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// Python :g 科学计数法边界: exp < -4 或 exp >= p (=6)
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if !(-4..6).contains(&exp) {
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let significand = value / 10_f64.powi(exp);
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let s = format!("{:.5}", significand);
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let s = s.trim_end_matches('0').trim_end_matches('.');
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return format!("{}e{:+03}", s, exp);
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}
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// 定点表示
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if abs >= 1.0 {
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let int_digits = exp as usize + 1;
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if int_digits >= 6 {
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return format!("{:.0}", value);
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}
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let s = format!("{:.prec$}", value, prec = 6 - int_digits);
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let s = s.trim_end_matches('0');
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s.trim_end_matches('.').to_string()
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} else {
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let leading_zeros = (-exp) as usize;
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let s = format!("{:.prec$}", value, prec = leading_zeros + 5);
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let s = s.trim_end_matches('0');
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s.trim_end_matches('.').to_string()
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_format_large() {
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assert_eq!(format_f64_g(82833.0), "82833");
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assert_eq!(format_f64_g(74192.2), "74192.2");
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assert_eq!(format_f64_g(100.0), "100");
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assert_eq!(format_f64_g(0.0), "0");
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assert_eq!(format_f64_g(12345.6789), "12345.7");
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}
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#[test]
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fn test_format_small() {
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assert_eq!(format_f64_g(0.001234), "0.001234");
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assert_eq!(format_f64_g(0.1), "0.1");
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assert_eq!(format_f64_g(0.001), "0.001");
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}
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#[test]
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fn test_format_extreme() {
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assert_eq!(format_f64_g(1e7), "1e+07");
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assert_eq!(format_f64_g(1e-5), "1e-05");
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}
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}
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