mirror of
https://github.com/sile/hls_m3u8.git
synced 2024-05-13 05:52:56 +00:00
312 lines
9 KiB
Rust
312 lines
9 KiB
Rust
use core::cmp::Ordering;
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use core::convert::TryFrom;
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use core::str::FromStr;
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use derive_more::{AsRef, Deref, Display};
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use crate::Error;
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/// A wrapper type around an [`f32`] that can not be constructed
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/// with [`NaN`], [`INFINITY`] or [`NEG_INFINITY`].
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///
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/// [`NaN`]: core::f32::NAN
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/// [`INFINITY`]: core::f32::INFINITY
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/// [`NEG_INFINITY`]: core::f32::NEG_INFINITY
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#[derive(AsRef, Deref, Default, Debug, Copy, Clone, Display)]
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pub struct Float(f32);
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impl Float {
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/// Makes a new [`Float`] from an [`f32`].
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///
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/// # Panics
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///
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/// If the given float is infinite or [`NaN`].
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///
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/// # Examples
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///
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/// ```
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/// # use hls_m3u8::types::Float;
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/// let float = Float::new(1.0);
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/// ```
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///
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/// This would panic:
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///
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/// ```should_panic
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/// # use hls_m3u8::types::Float;
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/// use core::f32::NAN;
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///
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/// let float = Float::new(NAN);
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/// ```
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///
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/// [`NaN`]: core::f32::NAN
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#[must_use]
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pub fn new(float: f32) -> Self {
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if float.is_infinite() {
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panic!("float must be finite: `{}`", float);
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}
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if float.is_nan() {
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panic!("float must not be `NaN`");
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}
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Self(float)
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}
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/// Returns the underlying [`f32`].
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///
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/// # Example
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///
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/// ```
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/// # use hls_m3u8::types::Float;
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/// assert_eq!(Float::new(1.1_f32).as_f32(), 1.1_f32);
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/// ```
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#[must_use]
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pub const fn as_f32(self) -> f32 { self.0 }
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}
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impl FromStr for Float {
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type Err = Error;
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fn from_str(input: &str) -> Result<Self, Self::Err> {
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let float = f32::from_str(input).map_err(|e| Error::parse_float(input, e))?;
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Self::try_from(float)
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}
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}
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impl TryFrom<f32> for Float {
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type Error = Error;
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fn try_from(float: f32) -> Result<Self, Self::Error> {
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if float.is_infinite() {
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return Err(Error::custom(format!("float must be finite: `{}`", float)));
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}
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if float.is_nan() {
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return Err(Error::custom("float must not be `NaN`"));
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}
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Ok(Self(float))
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}
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}
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macro_rules! implement_from {
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( $( $type:tt ),+ ) => {
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$(
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impl ::core::convert::From<$type> for Float {
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fn from(value: $type) -> Self {
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Self(value as f32)
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}
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}
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)+
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}
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}
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implement_from!(i16, u16, i8, u8);
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impl PartialEq for Float {
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#[inline]
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fn eq(&self, other: &Self) -> bool { self.0 == other.0 }
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}
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// convenience implementation to compare f32 with a Float.
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impl PartialEq<f32> for Float {
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#[inline]
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fn eq(&self, other: &f32) -> bool { &self.0 == other }
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}
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// In order to implement `Eq` a struct has to satisfy
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// the following requirements:
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// - reflexive: a == a;
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// - symmetric: a == b implies b == a; and
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// - transitive: a == b and b == c implies a == c.
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//
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// The symmetric and transitive parts are already satisfied
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// through `PartialEq`. The reflexive part is not satisfied for f32,
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// because `f32::NAN` never equals `f32::NAN`. (`assert!(f32::NAN, f32::NAN)`)
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//
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// It is ensured, that this struct can not be constructed
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// with NaN so all of the above requirements are satisfied and therefore Eq can
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// be soundly implemented.
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impl Eq for Float {}
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impl PartialOrd for Float {
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#[inline]
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fn partial_cmp(&self, other: &Self) -> Option<Ordering> { Some(self.cmp(other)) }
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}
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impl Ord for Float {
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#[inline]
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fn cmp(&self, other: &Self) -> Ordering {
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if self.0 < other.0 {
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Ordering::Less
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} else if self == other {
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Ordering::Equal
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} else {
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Ordering::Greater
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}
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}
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}
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/// The output of Hash cannot be relied upon to be stable. The same version of
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/// rust can return different values in different architectures. This is not a
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/// property of the Hasher that you’re using but instead of the way Hash happens
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/// to be implemented for the type you’re using (e.g., the current
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/// implementation of Hash for slices of integers returns different values in
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/// big and little-endian architectures).
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///
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/// See <https://internals.rust-lang.org/t/f32-f64-should-implement-hash/5436/33>
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#[doc(hidden)]
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impl ::core::hash::Hash for Float {
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fn hash<H>(&self, state: &mut H)
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where
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H: ::core::hash::Hasher,
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{
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// this implementation assumes, that the internal float is:
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// - not NaN
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// - neither negative nor positive infinity
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// to validate those assumptions debug_assertions are here
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// (those will be removed in a release build)
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debug_assert!(self.0.is_finite());
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debug_assert!(!self.0.is_nan());
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// this implementation is based on
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// https://internals.rust-lang.org/t/f32-f64-should-implement-hash/5436/33
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//
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// The important points are:
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// - NaN == NaN (Float does not allow NaN, so this should be satisfied)
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// - +0 == -0
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if self.0 == 0.0 || self.0 == -0.0 {
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state.write(&0.0_f32.to_be_bytes());
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} else {
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// I do not think it matters to differentiate between architectures, that use
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// big endian by default and those, that use little endian.
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state.write(&self.to_be_bytes())
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}
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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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use core::hash::{Hash, Hasher};
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use pretty_assertions::assert_eq;
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#[allow(clippy::all, clippy::unreadable_literal)]
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const PI: f32 = 3.14159265359;
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#[test]
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fn test_ord() {
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assert_eq!(Float::new(1.1).cmp(&Float::new(1.1)), Ordering::Equal);
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assert_eq!(Float::new(1.1).cmp(&Float::new(2.1)), Ordering::Less);
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assert_eq!(Float::new(1.1).cmp(&Float::new(0.1)), Ordering::Greater);
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}
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#[test]
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fn test_partial_ord() {
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assert_eq!(
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Float::new(1.1).partial_cmp(&Float::new(1.1)),
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Some(Ordering::Equal)
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);
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assert_eq!(
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Float::new(1.1).partial_cmp(&Float::new(2.1)),
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Some(Ordering::Less)
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);
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assert_eq!(
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Float::new(1.1).partial_cmp(&Float::new(0.1)),
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Some(Ordering::Greater)
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);
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}
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#[test]
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fn test_hash() {
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let mut hasher_left = std::collections::hash_map::DefaultHasher::new();
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let mut hasher_right = std::collections::hash_map::DefaultHasher::new();
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assert_eq!(
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Float::new(0.0).hash(&mut hasher_left),
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Float::new(-0.0).hash(&mut hasher_right)
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);
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assert_eq!(hasher_left.finish(), hasher_right.finish());
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let mut hasher_left = std::collections::hash_map::DefaultHasher::new();
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let mut hasher_right = std::collections::hash_map::DefaultHasher::new();
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assert_eq!(
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Float::new(1.0).hash(&mut hasher_left),
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Float::new(1.0).hash(&mut hasher_right)
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);
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assert_eq!(hasher_left.finish(), hasher_right.finish());
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}
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#[test]
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const fn test_eq() {
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struct _AssertEq
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where
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Float: Eq;
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}
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#[test]
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fn test_partial_eq() {
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assert_eq!(Float::new(1.0).eq(&Float::new(1.0)), true);
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assert_eq!(Float::new(1.0).eq(&Float::new(33.3)), false);
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assert_eq!(Float::new(1.1), 1.1);
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}
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#[test]
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fn test_display() {
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assert_eq!(Float::new(22.0).to_string(), "22".to_string());
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assert_eq!(Float::new(PI).to_string(), "3.1415927".to_string());
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assert_eq!(Float::new(-PI).to_string(), "-3.1415927".to_string());
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}
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#[test]
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fn test_parser() {
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assert_eq!(Float::new(22.0), Float::from_str("22").unwrap());
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assert_eq!(Float::new(-22.0), Float::from_str("-22").unwrap());
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assert_eq!(Float::new(PI), Float::from_str("3.14159265359").unwrap());
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assert!(Float::from_str("1#").is_err());
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assert!(Float::from_str("NaN").is_err());
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assert!(Float::from_str("inf").is_err());
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assert!(Float::from_str("-inf").is_err());
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}
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#[test]
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#[should_panic = "float must be finite: `inf`"]
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fn test_new_infinite() { let _ = Float::new(::core::f32::INFINITY); }
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#[test]
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#[should_panic = "float must be finite: `-inf`"]
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fn test_new_neg_infinite() { let _ = Float::new(::core::f32::NEG_INFINITY); }
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#[test]
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#[should_panic = "float must not be `NaN`"]
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fn test_new_nan() { let _ = Float::new(::core::f32::NAN); }
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#[test]
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fn test_as_f32() {
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assert_eq!(Float::new(1.1).as_f32(), 1.1_f32);
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}
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#[test]
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fn test_from() {
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assert_eq!(Float::from(-1_i8), Float::new(-1.0));
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assert_eq!(Float::from(1_u8), Float::new(1.0));
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assert_eq!(Float::from(-1_i16), Float::new(-1.0));
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assert_eq!(Float::from(1_u16), Float::new(1.0));
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}
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#[test]
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fn test_try_from() {
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assert_eq!(Float::try_from(1.1_f32).unwrap(), Float::new(1.1));
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assert_eq!(Float::try_from(-1.1_f32).unwrap(), Float::new(-1.1));
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assert!(Float::try_from(::core::f32::INFINITY).is_err());
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assert!(Float::try_from(::core::f32::NAN).is_err());
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assert!(Float::try_from(::core::f32::NEG_INFINITY).is_err());
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}
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}
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