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Copy pathfloat.rs
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310 lines (279 loc) · 9.99 KB
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use crate::format::Case;
use num_traits::{Float, Zero};
use std::f64;
pub fn parse_str(literal: &str) -> Option<f64> {
parse_inner(literal.trim().as_bytes())
}
pub fn parse_bytes(literal: &[u8]) -> Option<f64> {
parse_inner(trim_slice(literal, |b| b.is_ascii_whitespace()))
}
fn trim_slice<T>(v: &[T], mut trim: impl FnMut(&T) -> bool) -> &[T] {
let mut it = v.iter();
// it.take_while_ref(&mut trim).for_each(drop);
// hmm.. `&mut slice::Iter<_>` is not `Clone`
// it.by_ref().rev().take_while_ref(&mut trim).for_each(drop);
while it.clone().next().map_or(false, &mut trim) {
it.next();
}
while it.clone().next_back().map_or(false, &mut trim) {
it.next_back();
}
it.as_slice()
}
fn parse_inner(literal: &[u8]) -> Option<f64> {
use lexical_parse_float::{
format::PYTHON3_LITERAL, FromLexicalWithOptions, NumberFormatBuilder, Options,
};
// lexical-core's format::PYTHON_STRING is inaccurate
const PYTHON_STRING: u128 = NumberFormatBuilder::rebuild(PYTHON3_LITERAL)
.no_special(false)
.build();
f64::from_lexical_with_options::<PYTHON_STRING>(literal, &Options::new()).ok()
}
pub fn is_integer(v: f64) -> bool {
(v - v.round()).abs() < f64::EPSILON
}
fn format_nan(case: Case) -> String {
let nan = match case {
Case::Lower => "nan",
Case::Upper => "NAN",
};
nan.to_string()
}
fn format_inf(case: Case) -> String {
let inf = match case {
Case::Lower => "inf",
Case::Upper => "INF",
};
inf.to_string()
}
pub fn decimal_point_or_empty(precision: usize, alternate_form: bool) -> &'static str {
match (precision, alternate_form) {
(0, true) => ".",
_ => "",
}
}
pub fn format_fixed(precision: usize, magnitude: f64, case: Case, alternate_form: bool) -> String {
match magnitude {
magnitude if magnitude.is_finite() => {
let point = decimal_point_or_empty(precision, alternate_form);
format!("{magnitude:.precision$}{point}")
}
magnitude if magnitude.is_nan() => format_nan(case),
magnitude if magnitude.is_infinite() => format_inf(case),
_ => "".to_string(),
}
}
// Formats floats into Python style exponent notation, by first formatting in Rust style
// exponent notation (`1.0000e0`), then convert to Python style (`1.0000e+00`).
pub fn format_exponent(
precision: usize,
magnitude: f64,
case: Case,
alternate_form: bool,
) -> String {
match magnitude {
magnitude if magnitude.is_finite() => {
let r_exp = format!("{magnitude:.precision$e}");
let mut parts = r_exp.splitn(2, 'e');
let base = parts.next().unwrap();
let exponent = parts.next().unwrap().parse::<i64>().unwrap();
let e = match case {
Case::Lower => 'e',
Case::Upper => 'E',
};
let point = decimal_point_or_empty(precision, alternate_form);
format!("{base}{point}{e}{exponent:+#03}")
}
magnitude if magnitude.is_nan() => format_nan(case),
magnitude if magnitude.is_infinite() => format_inf(case),
_ => "".to_string(),
}
}
/// If s represents a floating point value, trailing zeros and a possibly trailing
/// decimal point will be removed.
/// This function does NOT work with decimal commas.
fn maybe_remove_trailing_redundant_chars(s: String, alternate_form: bool) -> String {
if !alternate_form && s.contains('.') {
// only truncate floating point values when not in alternate form
let s = remove_trailing_zeros(s);
remove_trailing_decimal_point(s)
} else {
s
}
}
fn remove_trailing_zeros(s: String) -> String {
let mut s = s;
while s.ends_with('0') {
s.pop();
}
s
}
fn remove_trailing_decimal_point(s: String) -> String {
let mut s = s;
if s.ends_with('.') {
s.pop();
}
s
}
pub fn format_general(
precision: usize,
magnitude: f64,
case: Case,
alternate_form: bool,
always_shows_fract: bool,
) -> String {
match magnitude {
magnitude if magnitude.is_finite() => {
let r_exp = format!("{:.*e}", precision.saturating_sub(1), magnitude);
let mut parts = r_exp.splitn(2, 'e');
let base = parts.next().unwrap();
let exponent = parts.next().unwrap().parse::<i64>().unwrap();
if exponent < -4 || exponent + (always_shows_fract as i64) >= (precision as i64) {
let e = match case {
Case::Lower => 'e',
Case::Upper => 'E',
};
let magnitude = format!("{:.*}", precision + 1, base);
let base = maybe_remove_trailing_redundant_chars(magnitude, alternate_form);
let point = decimal_point_or_empty(precision.saturating_sub(1), alternate_form);
format!("{base}{point}{e}{exponent:+#03}")
} else {
let precision = ((precision as i64) - 1 - exponent) as usize;
let magnitude = format!("{magnitude:.precision$}");
let base = maybe_remove_trailing_redundant_chars(magnitude, alternate_form);
let point = decimal_point_or_empty(precision, alternate_form);
format!("{base}{point}")
}
}
magnitude if magnitude.is_nan() => format_nan(case),
magnitude if magnitude.is_infinite() => format_inf(case),
_ => "".to_string(),
}
}
// TODO: rewrite using format_general
pub fn to_string(value: f64) -> String {
let lit = format!("{value:e}");
if let Some(position) = lit.find('e') {
let significand = &lit[..position];
let exponent = &lit[position + 1..];
let exponent = exponent.parse::<i32>().unwrap();
if exponent < 16 && exponent > -5 {
if is_integer(value) {
format!("{value:.1?}")
} else {
value.to_string()
}
} else {
format!("{significand}e{exponent:+#03}")
}
} else {
let mut s = value.to_string();
s.make_ascii_lowercase();
s
}
}
pub fn from_hex(s: &str) -> Option<f64> {
if let Ok(f) = hexf_parse::parse_hexf64(s, false) {
return Some(f);
}
match s.to_ascii_lowercase().as_str() {
"nan" | "+nan" | "-nan" => Some(f64::NAN),
"inf" | "infinity" | "+inf" | "+infinity" => Some(f64::INFINITY),
"-inf" | "-infinity" => Some(f64::NEG_INFINITY),
value => {
let mut hex = String::with_capacity(value.len());
let has_0x = value.contains("0x");
let has_p = value.contains('p');
let has_dot = value.contains('.');
let mut start = 0;
if !has_0x && value.starts_with('-') {
hex.push_str("-0x");
start += 1;
} else if !has_0x {
hex.push_str("0x");
if value.starts_with('+') {
start += 1;
}
}
for (index, ch) in value.chars().enumerate() {
if ch == 'p' {
if has_dot {
hex.push('p');
} else {
hex.push_str(".p");
}
} else if index >= start {
hex.push(ch);
}
}
if !has_p && has_dot {
hex.push_str("p0");
} else if !has_p && !has_dot {
hex.push_str(".p0")
}
hexf_parse::parse_hexf64(hex.as_str(), false).ok()
}
}
}
pub fn to_hex(value: f64) -> String {
let (mantissa, exponent, sign) = value.integer_decode();
let sign_fmt = if sign < 0 { "-" } else { "" };
match value {
value if value.is_zero() => format!("{sign_fmt}0x0.0p+0"),
value if value.is_infinite() => format!("{sign_fmt}inf"),
value if value.is_nan() => "nan".to_owned(),
_ => {
const BITS: i16 = 52;
const FRACT_MASK: u64 = 0xf_ffff_ffff_ffff;
format!(
"{}{:#x}.{:013x}p{:+}",
sign_fmt,
mantissa >> BITS,
mantissa & FRACT_MASK,
exponent + BITS
)
}
}
}
#[test]
fn test_to_hex() {
use rand::Rng;
for _ in 0..20000 {
let bytes = rand::thread_rng().gen::<[u64; 1]>();
let f = f64::from_bits(bytes[0]);
if !f.is_finite() {
continue;
}
let hex = to_hex(f);
// println!("{} -> {}", f, hex);
let roundtrip = hexf_parse::parse_hexf64(&hex, false).unwrap();
// println!(" -> {}", roundtrip);
assert!(f == roundtrip, "{} {} {}", f, hex, roundtrip);
}
}
#[test]
fn test_remove_trailing_zeros() {
assert!(remove_trailing_zeros(String::from("100")) == *"1");
assert!(remove_trailing_zeros(String::from("100.00")) == *"100.");
// leave leading zeros untouched
assert!(remove_trailing_zeros(String::from("001")) == *"001");
// leave strings untouched if they don't end with 0
assert!(remove_trailing_zeros(String::from("101")) == *"101");
}
#[test]
fn test_remove_trailing_decimal_point() {
assert!(remove_trailing_decimal_point(String::from("100.")) == *"100");
assert!(remove_trailing_decimal_point(String::from("1.")) == *"1");
// leave leading decimal points untouched
assert!(remove_trailing_decimal_point(String::from(".5")) == *".5");
}
#[test]
fn test_maybe_remove_trailing_redundant_chars() {
assert!(maybe_remove_trailing_redundant_chars(String::from("100."), true) == *"100.");
assert!(maybe_remove_trailing_redundant_chars(String::from("100."), false) == *"100");
assert!(maybe_remove_trailing_redundant_chars(String::from("1."), false) == *"1");
assert!(maybe_remove_trailing_redundant_chars(String::from("10.0"), false) == *"10");
// don't truncate integers
assert!(maybe_remove_trailing_redundant_chars(String::from("1000"), false) == *"1000");
}