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Copy pathfloat_ops.rs
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524 lines (479 loc) · 16.1 KB
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use num_bigint::{BigInt, ToBigInt};
use num_traits::{Float, Signed, ToPrimitive, Zero};
use std::f64;
pub fn ufrexp(value: f64) -> (f64, i32) {
if 0.0 == value {
(0.0, 0i32)
} else {
let bits = value.to_bits();
let exponent: i32 = ((bits >> 52) & 0x7ff) as i32 - 1022;
let mantissa_bits = bits & (0x000f_ffff_ffff_ffff) | (1022 << 52);
(f64::from_bits(mantissa_bits), exponent)
}
}
/// Equate an integer to a float.
///
/// Returns true if and only if, when converted to each others types, both are equal.
///
/// # Examples
///
/// ```
/// use num_bigint::BigInt;
/// use rustpython_common::float_ops::eq_int;
/// let a = 1.0f64;
/// let b = BigInt::from(1);
/// let c = 2.0f64;
/// assert!(eq_int(a, &b));
/// assert!(!eq_int(c, &b));
/// ```
///
pub fn eq_int(value: f64, other: &BigInt) -> bool {
if let (Some(self_int), Some(other_float)) = (value.to_bigint(), other.to_f64()) {
value == other_float && self_int == *other
} else {
false
}
}
pub fn lt_int(value: f64, other_int: &BigInt) -> bool {
match (value.to_bigint(), other_int.to_f64()) {
(Some(self_int), Some(other_float)) => value < other_float || self_int < *other_int,
// finite float, other_int too big for float,
// the result depends only on other_int’s sign
(Some(_), None) => other_int.is_positive(),
// infinite float must be bigger or lower than any int, depending on its sign
_ if value.is_infinite() => value.is_sign_negative(),
// NaN, always false
_ => false,
}
}
pub fn gt_int(value: f64, other_int: &BigInt) -> bool {
match (value.to_bigint(), other_int.to_f64()) {
(Some(self_int), Some(other_float)) => value > other_float || self_int > *other_int,
// finite float, other_int too big for float,
// the result depends only on other_int’s sign
(Some(_), None) => other_int.is_negative(),
// infinite float must be bigger or lower than any int, depending on its sign
_ if value.is_infinite() => value.is_sign_positive(),
// NaN, always false
_ => false,
}
}
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
}
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Case {
Lower,
Upper,
}
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(),
}
}
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
)
}
}
}
pub fn div(v1: f64, v2: f64) -> Option<f64> {
if v2 != 0.0 {
Some(v1 / v2)
} else {
None
}
}
pub fn mod_(v1: f64, v2: f64) -> Option<f64> {
if v2 != 0.0 {
let val = v1 % v2;
match (v1.signum() as i32, v2.signum() as i32) {
(1, 1) | (-1, -1) => Some(val),
_ if (v1 == 0.0) || (v1.abs() == v2.abs()) => Some(val.copysign(v2)),
_ => Some((val + v2).copysign(v2)),
}
} else {
None
}
}
pub fn floordiv(v1: f64, v2: f64) -> Option<f64> {
if v2 != 0.0 {
Some((v1 / v2).floor())
} else {
None
}
}
pub fn divmod(v1: f64, v2: f64) -> Option<(f64, f64)> {
if v2 != 0.0 {
let mut m = v1 % v2;
let mut d = (v1 - m) / v2;
if v2.is_sign_negative() != m.is_sign_negative() {
m += v2;
d -= 1.0;
}
Some((d, m))
} else {
None
}
}
// nextafter algorithm based off of https://gitlab.com/bronsonbdevost/next_afterf
#[allow(clippy::float_cmp)]
pub fn nextafter(x: f64, y: f64) -> f64 {
if x == y {
y
} else if x.is_nan() || y.is_nan() {
f64::NAN
} else if x >= f64::INFINITY {
f64::MAX
} else if x <= f64::NEG_INFINITY {
f64::MIN
} else if x == 0.0 {
f64::from_bits(1).copysign(y)
} else {
// next x after 0 if y is farther from 0 than x, otherwise next towards 0
// the sign is a separate bit in floats, so bits+1 moves away from 0 no matter the float
let b = x.to_bits();
let bits = if (y > x) == (x > 0.0) { b + 1 } else { b - 1 };
let ret = f64::from_bits(bits);
if ret == 0.0 {
ret.copysign(x)
} else {
ret
}
}
}
pub fn ulp(x: f64) -> f64 {
if x.is_nan() {
return x;
}
let x = x.abs();
let x2 = nextafter(x, f64::INFINITY);
if x2.is_infinite() {
// special case: x is the largest positive representable float
let x2 = nextafter(x, f64::NEG_INFINITY);
x - x2
} else {
x2 - x
}
}
pub fn round_float_digits(x: f64, ndigits: i32) -> Option<f64> {
let float = if ndigits.is_zero() {
let fract = x.fract();
if (fract.abs() - 0.5).abs() < f64::EPSILON {
if x.trunc() % 2.0 == 0.0 {
x - fract
} else {
x + fract
}
} else {
x.round()
}
} else {
const NDIGITS_MAX: i32 =
((f64::MANTISSA_DIGITS as i32 - f64::MIN_EXP) as f64 * f64::consts::LOG10_2) as i32;
const NDIGITS_MIN: i32 = -(((f64::MAX_EXP + 1) as f64 * f64::consts::LOG10_2) as i32);
if ndigits > NDIGITS_MAX {
x
} else if ndigits < NDIGITS_MIN {
0.0f64.copysign(x)
} else {
let (y, pow1, pow2) = if ndigits >= 0 {
// according to cpython: pow1 and pow2 are each safe from overflow, but
// pow1*pow2 ~= pow(10.0, ndigits) might overflow
let (pow1, pow2) = if ndigits > 22 {
(10.0.powf((ndigits - 22) as f64), 1e22)
} else {
(10.0.powf(ndigits as f64), 1.0)
};
let y = (x * pow1) * pow2;
if !y.is_finite() {
return Some(x);
}
(y, pow1, Some(pow2))
} else {
let pow1 = 10.0.powf((-ndigits) as f64);
(x / pow1, pow1, None)
};
let z = y.round();
#[allow(clippy::float_cmp)]
let z = if (y - z).abs() == 0.5 {
2.0 * (y / 2.0).round()
} else {
z
};
let z = if let Some(pow2) = pow2 {
// ndigits >= 0
(z / pow2) / pow1
} else {
z * pow1
};
if !z.is_finite() {
// overflow
return None;
}
z
}
};
Some(float)
}
#[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");
}