dec2flt: Rename fields to be consistent with documented notation

Author: tgross35

library/core/src/num/dec2flt/common.rs

@@ -63,19 +63,20 @@ pub(crate) fn is_8digits(v: u64) -> bool {
     (a | b) & 0x8080_8080_8080_8080 == 0
 }
 
-/// A custom 64-bit floating point type, representing `f * 2^e`.
-/// e is biased, so it be directly shifted into the exponent bits.
+/// A custom 64-bit floating point type, representing `m * 2^p`.
+/// p is biased, so it be directly shifted into the exponent bits.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Default)]
 pub struct BiasedFp {
     /// The significant digits.
-    pub f: u64,
+    pub m: u64,
     /// The biased, binary exponent.
-    pub e: i32,
+    pub p_biased: i32,
 }
 
 impl BiasedFp {
+    /// Represent `0 ^ p`
     #[inline]
-    pub const fn zero_pow2(e: i32) -> Self {
-        Self { f: 0, e }
+    pub const fn zero_pow2(p_biased: i32) -> Self {
+        Self { m: 0, p_biased }
     }
 }

library/core/src/num/dec2flt/lemire.rs

@@ -73,7 +73,7 @@ pub fn compute_float<F: RawFloat>(q: i64, mut w: u64) -> BiasedFp {
         mantissa += mantissa & 1;
         mantissa >>= 1;
         power2 = (mantissa >= (1_u64 << F::MANTISSA_EXPLICIT_BITS)) as i32;
-        return BiasedFp { f: mantissa, e: power2 };
+        return BiasedFp { m: mantissa, p_biased: power2 };
     }
     // Need to handle rounding ties. Normally, we need to round up,
     // but if we fall right in between and we have an even basis, we
@@ -111,7 +111,7 @@ pub fn compute_float<F: RawFloat>(q: i64, mut w: u64) -> BiasedFp {
         // Exponent is above largest normal value, must be infinite.
         return fp_inf;
     }
-    BiasedFp { f: mantissa, e: power2 }
+    BiasedFp { m: mantissa, p_biased: power2 }
 }
 
 /// Calculate a base 2 exponent from a decimal exponent.

library/core/src/num/dec2flt/mod.rs

@@ -233,8 +233,8 @@ pub fn pfe_invalid() -> ParseFloatError {
 
 /// Converts a `BiasedFp` to the closest machine float type.
 fn biased_fp_to_float<T: RawFloat>(x: BiasedFp) -> T {
-    let mut word = x.f;
-    word |= (x.e as u64) << T::MANTISSA_EXPLICIT_BITS;
+    let mut word = x.m;
+    word |= (x.p_biased as u64) << T::MANTISSA_EXPLICIT_BITS;
     T::from_u64_bits(word)
 }
 
@@ -272,12 +272,15 @@ pub fn dec2flt<F: RawFloat>(s: &str) -> Result<F, ParseFloatError> {
     // redundantly using the Eisel-Lemire algorithm if it was unable to
     // correctly round on the first pass.
     let mut fp = compute_float::<F>(num.exponent, num.mantissa);
-    if num.many_digits && fp.e >= 0 && fp != compute_float::<F>(num.exponent, num.mantissa + 1) {
-        fp.e = -1;
+    if num.many_digits
+        && fp.p_biased >= 0
+        && fp != compute_float::<F>(num.exponent, num.mantissa + 1)
+    {
+        fp.p_biased = -1;
     }
     // Unable to correctly round the float using the Eisel-Lemire algorithm.
     // Fallback to a slower, but always correct algorithm.
-    if fp.e < 0 {
+    if fp.p_biased < 0 {
         fp = parse_long_mantissa::<F>(s);
     }
 

library/core/src/num/dec2flt/slow.rs

@@ -105,5 +105,5 @@ pub(crate) fn parse_long_mantissa<F: RawFloat>(s: &[u8]) -> BiasedFp {
     }
     // Zero out all the bits above the explicit mantissa bits.
     mantissa &= (1_u64 << F::MANTISSA_EXPLICIT_BITS) - 1;
-    BiasedFp { f: mantissa, e: power2 }
+    BiasedFp { m: mantissa, p_biased: power2 }
 }

library/core/tests/num/dec2flt/float.rs

@@ -12,8 +12,8 @@ fn test_f32_integer_decode() {
 
     // Ignore the "sign" (quiet / signalling flag) of NAN.
     // It can vary between runtime operations and LLVM folding.
-    let (nan_m, nan_e, _nan_s) = f32::NAN.integer_decode();
-    assert_eq!((nan_m, nan_e), (12582912, 105));
+    let (nan_m, nan_p, _nan_s) = f32::NAN.integer_decode();
+    assert_eq!((nan_m, nan_p), (12582912, 105));
 }
 
 #[test]
@@ -28,6 +28,6 @@ fn test_f64_integer_decode() {
 
     // Ignore the "sign" (quiet / signalling flag) of NAN.
     // It can vary between runtime operations and LLVM folding.
-    let (nan_m, nan_e, _nan_s) = f64::NAN.integer_decode();
-    assert_eq!((nan_m, nan_e), (6755399441055744, 972));
+    let (nan_m, nan_p, _nan_s) = f64::NAN.integer_decode();
+    assert_eq!((nan_m, nan_p), (6755399441055744, 972));
 }

library/core/tests/num/dec2flt/lemire.rs

@@ -2,12 +2,12 @@ use core::num::dec2flt::lemire::compute_float;
 
 fn compute_float32(q: i64, w: u64) -> (i32, u64) {
     let fp = compute_float::<f32>(q, w);
-    (fp.e, fp.f)
+    (fp.p_biased, fp.m)
 }
 
 fn compute_float64(q: i64, w: u64) -> (i32, u64) {
     let fp = compute_float::<f64>(q, w);
-    (fp.e, fp.f)
+    (fp.p_biased, fp.m)
 }
 
 #[test]