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Copy pathfloat_ops.rs
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364 lines (329 loc) · 10.6 KB
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use num_bigint::{BigInt, ToBigInt};
use num_traits::{Float, Signed, ToPrimitive, Zero};
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)
}
}
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> {
if literal.starts_with('_') || literal.ends_with('_') {
return None;
}
let mut buf = String::with_capacity(literal.len());
let mut last_tok: Option<char> = None;
for c in literal.chars() {
if !(c.is_ascii_alphanumeric() || c == '_' || c == '+' || c == '-' || c == '.') {
return None;
}
if !c.is_ascii_alphanumeric() {
if let Some(l) = last_tok {
if !l.is_ascii_alphanumeric() && !(c == '.' && (l == '-' || l == '+')) {
return None;
}
}
}
if c != '_' {
buf.push(c);
}
last_tok = Some(c);
}
if let Ok(f) = lexical_core::parse(buf.as_bytes()) {
Some(f)
} else {
None
}
}
pub fn is_integer(v: f64) -> bool {
(v - v.round()).abs() < std::f64::EPSILON
}
#[derive(Debug)]
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 format_fixed(precision: usize, magnitude: f64, case: Case) -> String {
match magnitude {
magnitude if magnitude.is_finite() => format!("{:.*}", precision, magnitude),
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) -> String {
match magnitude {
magnitude if magnitude.is_finite() => {
let r_exp = format!("{:.*e}", precision, magnitude);
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',
};
format!("{}{}{:+#03}", base, e, exponent)
}
magnitude if magnitude.is_nan() => format_nan(case),
magnitude if magnitude.is_infinite() => format_inf(case),
_ => "".to_string(),
}
}
fn remove_trailing_zeros(s: String) -> String {
let mut s = s;
while s.ends_with('0') || s.ends_with('.') {
s.truncate(s.len() - 1);
}
s
}
pub fn format_general(precision: usize, magnitude: f64, case: Case) -> 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 >= (precision as i64) {
let e = match case {
Case::Lower => 'e',
Case::Upper => 'E',
};
let base = remove_trailing_zeros(format!("{:.*}", precision + 1, base));
format!("{}{}{:+#03}", base, e, exponent)
} else {
let precision = (precision as i64) - 1 - exponent;
let precision = precision as usize;
remove_trailing_zeros(format!("{:.*}", precision, magnitude))
}
}
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!("{:e}", value);
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!("{:.1?}", value)
} else {
value.to_string()
}
} else {
format!("{}e{:+#03}", significand, exponent)
}
} else {
value.to_string()
}
}
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!("{}0x0.0p+0", sign_fmt),
value if value.is_infinite() => format!("{}inf", sign_fmt),
value if value.is_nan() => "nan".to_owned(),
_ => {
const BITS: i16 = 52;
const FRACT_MASK: u64 = 0xf_ffff_ffff_ffff;
format!(
"{}0x{: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 mut val = v1 % v2;
if (val < 0.0) != (v2 < 0.0) {
val += v2;
}
Some(val)
} 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
}
}
#[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);
}
}
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