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//! IEEE 754 floating point compliance tests
//!
//! To understand IEEE 754's requirements on a programming language, one must understand that the
//! requirements of IEEE 754 rest on the total programming environment, and not entirely on any
//! one component. That means the hardware, language, and even libraries are considered part of
//! conforming floating point support in a programming environment.
//!
//! A programming language's duty, accordingly, is:
//! 1. offer access to the hardware where the hardware offers support
//! 2. provide operations that fulfill the remaining requirements of the standard
//! 3. provide the ability to write additional software that can fulfill those requirements
//!
//! This may be fulfilled in any combination that the language sees fit. However, to claim that
//! a language supports IEEE 754 is to suggest that it has fulfilled requirements 1 and 2, without
//! deferring minimum requirements to libraries. This is because support for IEEE 754 is defined
//! as complete support for at least one specified floating point type as an "arithmetic" and
//! "interchange" format, plus specified type conversions to "external character sequences" and
//! integer types.
//!
//! For our purposes,
//! "interchange format" => f32, f64
//! "arithmetic format" => f32, f64, and any "soft floats"
//! "external character sequence" => str from any float
//! "integer format" => {i,u}{8,16,32,64,128}
//!
//! None of these tests are against Rust's own implementation. They are only tests against the
//! standard. That is why they accept wildly diverse inputs or may seem to duplicate other tests.
//! Please consider this carefully when adding, removing, or reorganizing these tests. They are
//! here so that it is clear what tests are required by the standard and what can be changed.
use ::core::str::FromStr;
// IEEE 754 for many tests is applied to specific bit patterns.
// These generally are not applicable to NaN, however.
macro_rules! assert_biteq {
($lhs:expr, $rhs:expr) => {
assert_eq!($lhs.to_bits(), $rhs.to_bits())
};
}
// ToString uses the default fmt::Display impl without special concerns, and bypasses other parts
// of the formatting infrastructure, which makes it ideal for testing here.
#[allow(unused_macros)]
macro_rules! roundtrip {
($f:expr => $t:ty) => {
($f).to_string().parse::<$t>().unwrap()
};
}
macro_rules! assert_floats_roundtrip {
($f:ident) => {
assert_biteq!(f32::$f, roundtrip!(f32::$f => f32));
assert_biteq!(f64::$f, roundtrip!(f64::$f => f64));
};
($f:expr) => {
assert_biteq!($f as f32, roundtrip!($f => f32));
assert_biteq!($f as f64, roundtrip!($f => f64));
}
}
macro_rules! assert_floats_bitne {
($lhs:ident, $rhs:ident) => {
assert_ne!(f32::$lhs.to_bits(), f32::$rhs.to_bits());
assert_ne!(f64::$lhs.to_bits(), f64::$rhs.to_bits());
};
($lhs:expr, $rhs:expr) => {
assert_ne!(f32::to_bits($lhs), f32::to_bits($rhs));
assert_ne!(f64::to_bits($lhs), f64::to_bits($rhs));
};
}
// We must preserve signs on all numbers. That includes zero.
// -0 and 0 are == normally, so test bit equality.
#[test]
fn preserve_signed_zero() {
assert_floats_roundtrip!(-0.0);
assert_floats_roundtrip!(0.0);
assert_floats_bitne!(0.0, -0.0);
}
#[test]
fn preserve_signed_infinity() {
assert_floats_roundtrip!(INFINITY);
assert_floats_roundtrip!(NEG_INFINITY);
assert_floats_bitne!(INFINITY, NEG_INFINITY);
}
#[test]
fn infinity_to_str() {
assert!(match f32::INFINITY.to_string().to_lowercase().as_str() {
"+infinity" | "infinity" => true,
"+inf" | "inf" => true,
_ => false,
});
assert!(
match f64::INFINITY.to_string().to_lowercase().as_str() {
"+infinity" | "infinity" => true,
"+inf" | "inf" => true,
_ => false,
},
"Infinity must write to a string as some casing of inf or infinity, with an optional +."
);
}
#[test]
fn neg_infinity_to_str() {
assert!(match f32::NEG_INFINITY.to_string().to_lowercase().as_str() {
"-infinity" | "-inf" => true,
_ => false,
});
assert!(
match f64::NEG_INFINITY.to_string().to_lowercase().as_str() {
"-infinity" | "-inf" => true,
_ => false,
},
"Negative Infinity must write to a string as some casing of -inf or -infinity"
)
}
#[test]
fn nan_to_str() {
assert!(
match f32::NAN.to_string().to_lowercase().as_str() {
"nan" | "+nan" | "-nan" => true,
_ => false,
},
"NaNs must write to a string as some casing of nan."
)
}
// "+"?("inf"|"infinity") in any case => Infinity
#[test]
fn infinity_from_str() {
assert_biteq!(f32::INFINITY, f32::from_str("infinity").unwrap());
assert_biteq!(f32::INFINITY, f32::from_str("inf").unwrap());
assert_biteq!(f32::INFINITY, f32::from_str("+infinity").unwrap());
assert_biteq!(f32::INFINITY, f32::from_str("+inf").unwrap());
// yes! this means you are weLcOmE tO mY iNfInItElY tWiStEd MiNd
assert_biteq!(f32::INFINITY, f32::from_str("+iNfInItY").unwrap());
}
// "-inf"|"-infinity" in any case => Negative Infinity
#[test]
fn neg_infinity_from_str() {
assert_biteq!(f32::NEG_INFINITY, f32::from_str("-infinity").unwrap());
assert_biteq!(f32::NEG_INFINITY, f32::from_str("-inf").unwrap());
assert_biteq!(f32::NEG_INFINITY, f32::from_str("-INF").unwrap());
assert_biteq!(f32::NEG_INFINITY, f32::from_str("-INFinity").unwrap());
}
// ("+"|"-"")?"s"?"nan" in any case => qNaN
#[test]
fn qnan_from_str() {
assert!("nan".parse::<f32>().unwrap().is_nan());
assert!("-nan".parse::<f32>().unwrap().is_nan());
assert!("+nan".parse::<f32>().unwrap().is_nan());
assert!("+NAN".parse::<f32>().unwrap().is_nan());
assert!("-NaN".parse::<f32>().unwrap().is_nan());
}
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