Add unit tests for integer_decode_f32 and integer_decode_f64

Author: mtilda

src/float.rs

@@ -2397,6 +2397,94 @@ mod tests {
         check::<f64>(1e-12);
     }
 
+    #[test]
+    #[cfg(any(feature = "std", feature = "libm"))]
+    fn integer_decode_f32() {
+        use crate::Float;
+        use core::f32;
+        use std::format;
+
+        fn check(x: f32, x_mantissa: u64, x_exponent: i16, x_sign: i8) {
+            let (mantissa, exponent, sign) = Float::integer_decode(x);
+            assert!(
+                (x_mantissa, x_exponent, x_sign) == (mantissa, exponent, sign),
+                "{}\n\t{}\n\t{}",
+                format!("while testing return value of Float::integer_decode({})", x),
+                format!("expected: ({:#x} {} {})", x_mantissa, x_exponent, x_sign),
+                format!("   found: ({:#x} {} {})", mantissa, exponent, sign),
+            );
+
+            let sign_f = sign as f32;
+            let mantissa_f = mantissa as f32;
+            let exponent_f = exponent as f32;
+
+            let abs_difference = (sign_f * mantissa_f * 2_f32.powf(exponent_f) - x).abs();
+
+            assert!(abs_difference < 1e-10, "absolute difference {} must be less than 1e-10", abs_difference);
+        }
+
+        for sign in [1, -1] {
+            let sign_f = sign as f32;
+            check(sign_f * 0.0_f32, 0x000000, -150, sign);
+            check(sign_f * f32::MIN_POSITIVE, 0x800000, -149, sign);
+            check(sign_f * 0.25_f32, 0x800000, -25, sign);
+            check(sign_f * 0.5_f32, 0x800000, -24, sign);
+            check(sign_f * 1_f32, 0x800000, -23, sign);
+            check(sign_f * 1.5_f32, 0xc00000, -23, sign);
+            check(sign_f * 2_f32, 0x800000, -22, sign);
+            check(sign_f * 2.5_f32, 0xa00000, -22, sign);
+            check(sign_f * 3_f32, 0xc00000, -22, sign);
+            check(sign_f * 4_f32, 0x800000, -21, sign);
+            check(sign_f * 5_f32, 0xa00000, -21, sign);
+            check(sign_f * 42_f32, 0xa80000, -18, sign);
+            check(sign_f * f32::MAX, 0xffffff, 104, sign);
+        }
+    }
+
+    #[test]
+    #[cfg(any(feature = "std", feature = "libm"))]
+    fn integer_decode_f64() {
+        use crate::Float;
+        use core::f64;
+        use std::format;
+
+        fn check(x: f64, x_mantissa: u64, x_exponent: i16, x_sign: i8) {
+            let (mantissa, exponent, sign) = Float::integer_decode(x);
+            assert!(
+                (x_mantissa, x_exponent, x_sign) == (mantissa, exponent, sign),
+                "{}\n\t{}\n\t{}",
+                format!("while testing return value of Float::integer_decode({})", x),
+                format!("expected: ({:#x} {} {})", x_mantissa, x_exponent, x_sign),
+                format!("   found: ({:#x} {} {})", mantissa, exponent, sign),
+            );
+
+            let sign_f = sign as f64;
+            let mantissa_f = mantissa as f64;
+            let exponent_f = exponent as f64;
+
+            let abs_difference = (sign_f * mantissa_f * 2_f64.powf(exponent_f) - x).abs();
+
+            assert!(abs_difference < 1e-10, "absolute difference {} must be less than 1e-10", abs_difference);
+        }
+
+        for sign in [1, -1] {
+            let sign_f = sign as f64;
+            check(sign_f * 0.0_f64, 0x00000000000000, -1075, sign);
+            check(sign_f * f64::MIN_POSITIVE, 0x10000000000000, -1074, sign);
+            check(sign_f * 0.25_f64, 0x10000000000000, -54, sign);
+            check(sign_f * 0.5_f64, 0x10000000000000, -53, sign);
+            check(sign_f * 1_f64, 0x10000000000000, -52, sign);
+            check(sign_f * 1.5_f64, 0x18000000000000, -52, sign);
+            check(sign_f * 2_f64, 0x10000000000000, -51, sign);
+            check(sign_f * 2.5_f64, 0x14000000000000, -51, sign);
+            check(sign_f * 3_f64, 0x18000000000000, -51, sign);
+            check(sign_f * 4_f64, 0x10000000000000, -50, sign);
+            check(sign_f * 5_f64, 0x14000000000000, -50, sign);
+            check(sign_f * 42_f64, 0x15000000000000, -47, sign);
+            check(sign_f * f64::MAX, 0x1fffffffffffff, 971, sign);
+        }
+    }
+
     #[test]
     #[cfg(any(feature = "std", feature = "libm"))]
     fn copysign() {