Merge #163

163: Extended the result of to_f32/to_f64 with infinity r=cuviper a=notoria



Co-authored-by: notoria <notoria@users.noreply.github.com>

Author: bors[bot]

Cargo.toml

@@ -8,7 +8,7 @@ categories = [ "algorithms", "data-structures", "science" ]
 license = "MIT/Apache-2.0"
 name = "num-bigint"
 repository = "https://github.com/rust-num/num-bigint"
-version = "0.3.0"
+version = "0.3.1"
 readme = "README.md"
 build = "build.rs"
 exclude = ["/bors.toml", "/ci/*", "/.github/*"]

src/biguint.rs

@@ -1687,19 +1687,22 @@ impl Roots for BigUint {
         let max_bits = bits / n64 + 1;
 
         #[cfg(feature = "std")]
-        let guess = if let Some(f) = self.to_f64() {
-            // We fit in `f64` (lossy), so get a better initial guess from that.
-            BigUint::from_f64((f.ln() / f64::from(n)).exp()).unwrap()
-        } else {
-            // Try to guess by scaling down such that it does fit in `f64`.
-            // With some (x * 2ⁿᵏ), its nth root ≈ (ⁿ√x * 2ᵏ)
-            let extra_bits = bits - (f64::MAX_EXP as u64 - 1);
-            let root_scale = extra_bits.div_ceil(&n64);
-            let scale = root_scale * n64;
-            if scale < bits && bits - scale > n64 {
-                (self >> scale).nth_root(n) << root_scale
-            } else {
-                BigUint::one() << max_bits
+        let guess = match self.to_f64() {
+            Some(f) if f.is_finite() => {
+                // We fit in `f64` (lossy), so get a better initial guess from that.
+                BigUint::from_f64((f.ln() / f64::from(n)).exp()).unwrap()
+            }
+            _ => {
+                // Try to guess by scaling down such that it does fit in `f64`.
+                // With some (x * 2ⁿᵏ), its nth root ≈ (ⁿ√x * 2ᵏ)
+                let extra_bits = bits - (f64::MAX_EXP as u64 - 1);
+                let root_scale = extra_bits.div_ceil(&n64);
+                let scale = root_scale * n64;
+                if scale < bits && bits - scale > n64 {
+                    (self >> scale).nth_root(n) << root_scale
+                } else {
+                    BigUint::one() << max_bits
+                }
             }
         };
 
@@ -1730,16 +1733,19 @@ impl Roots for BigUint {
         let max_bits = bits / 2 + 1;
 
         #[cfg(feature = "std")]
-        let guess = if let Some(f) = self.to_f64() {
-            // We fit in `f64` (lossy), so get a better initial guess from that.
-            BigUint::from_f64(f.sqrt()).unwrap()
-        } else {
-            // Try to guess by scaling down such that it does fit in `f64`.
-            // With some (x * 2²ᵏ), its sqrt ≈ (√x * 2ᵏ)
-            let extra_bits = bits - (f64::MAX_EXP as u64 - 1);
-            let root_scale = (extra_bits + 1) / 2;
-            let scale = root_scale * 2;
-            (self >> scale).sqrt() << root_scale
+        let guess = match self.to_f64() {
+            Some(f) if f.is_finite() => {
+                // We fit in `f64` (lossy), so get a better initial guess from that.
+                BigUint::from_f64(f.sqrt()).unwrap()
+            }
+            _ => {
+                // Try to guess by scaling down such that it does fit in `f64`.
+                // With some (x * 2²ᵏ), its sqrt ≈ (√x * 2ᵏ)
+                let extra_bits = bits - (f64::MAX_EXP as u64 - 1);
+                let root_scale = (extra_bits + 1) / 2;
+                let scale = root_scale * 2;
+                (self >> scale).sqrt() << root_scale
+            }
         };
 
         #[cfg(not(feature = "std"))]
@@ -1766,16 +1772,19 @@ impl Roots for BigUint {
         let max_bits = bits / 3 + 1;
 
         #[cfg(feature = "std")]
-        let guess = if let Some(f) = self.to_f64() {
-            // We fit in `f64` (lossy), so get a better initial guess from that.
-            BigUint::from_f64(f.cbrt()).unwrap()
-        } else {
-            // Try to guess by scaling down such that it does fit in `f64`.
-            // With some (x * 2³ᵏ), its cbrt ≈ (∛x * 2ᵏ)
-            let extra_bits = bits - (f64::MAX_EXP as u64 - 1);
-            let root_scale = (extra_bits + 2) / 3;
-            let scale = root_scale * 3;
-            (self >> scale).cbrt() << root_scale
+        let guess = match self.to_f64() {
+            Some(f) if f.is_finite() => {
+                // We fit in `f64` (lossy), so get a better initial guess from that.
+                BigUint::from_f64(f.cbrt()).unwrap()
+            }
+            _ => {
+                // Try to guess by scaling down such that it does fit in `f64`.
+                // With some (x * 2³ᵏ), its cbrt ≈ (∛x * 2ᵏ)
+                let extra_bits = bits - (f64::MAX_EXP as u64 - 1);
+                let root_scale = (extra_bits + 2) / 3;
+                let scale = root_scale * 3;
+                (self >> scale).cbrt() << root_scale
+            }
         };
 
         #[cfg(not(feature = "std"))]
@@ -1870,14 +1879,9 @@ impl ToPrimitive for BigUint {
         let exponent = self.bits() - u64::from(fls(mantissa));
 
         if exponent > f32::MAX_EXP as u64 {
-            None
+            Some(f32::INFINITY)
         } else {
-            let ret = (mantissa as f32) * 2.0f32.powi(exponent as i32);
-            if ret.is_infinite() {
-                None
-            } else {
-                Some(ret)
-            }
+            Some((mantissa as f32) * 2.0f32.powi(exponent as i32))
         }
     }
 
@@ -1887,14 +1891,9 @@ impl ToPrimitive for BigUint {
         let exponent = self.bits() - u64::from(fls(mantissa));
 
         if exponent > f64::MAX_EXP as u64 {
-            None
+            Some(f64::INFINITY)
         } else {
-            let ret = (mantissa as f64) * 2.0f64.powi(exponent as i32);
-            if ret.is_infinite() {
-                None
-            } else {
-                Some(ret)
-            }
+            Some((mantissa as f64) * 2.0f64.powi(exponent as i32))
         }
     }
 }

tests/bigint.rs

@@ -448,14 +448,23 @@ fn test_convert_f32() {
     // largest BigInt that will round to a finite f32 value
     let big_num = (BigInt::one() << 128u8) - 1u8 - (BigInt::one() << (128u8 - 25));
     assert_eq!(big_num.to_f32(), Some(f32::MAX));
-    assert_eq!((&big_num + 1u8).to_f32(), None);
+    assert_eq!((&big_num + 1u8).to_f32(), Some(f32::INFINITY));
     assert_eq!((-&big_num).to_f32(), Some(f32::MIN));
-    assert_eq!(((-&big_num) - 1u8).to_f32(), None);
+    assert_eq!(((-&big_num) - 1u8).to_f32(), Some(f32::NEG_INFINITY));
 
-    assert_eq!(((BigInt::one() << 128u8) - 1u8).to_f32(), None);
-    assert_eq!((BigInt::one() << 128u8).to_f32(), None);
-    assert_eq!((-((BigInt::one() << 128u8) - 1u8)).to_f32(), None);
-    assert_eq!((-(BigInt::one() << 128u8)).to_f32(), None);
+    assert_eq!(
+        ((BigInt::one() << 128u8) - 1u8).to_f32(),
+        Some(f32::INFINITY)
+    );
+    assert_eq!((BigInt::one() << 128u8).to_f32(), Some(f32::INFINITY));
+    assert_eq!(
+        (-((BigInt::one() << 128u8) - 1u8)).to_f32(),
+        Some(f32::NEG_INFINITY)
+    );
+    assert_eq!(
+        (-(BigInt::one() << 128u8)).to_f32(),
+        Some(f32::NEG_INFINITY)
+    );
 }
 
 #[test]
@@ -529,14 +538,23 @@ fn test_convert_f64() {
     // largest BigInt that will round to a finite f64 value
     let big_num = (BigInt::one() << 1024u16) - 1u8 - (BigInt::one() << (1024u16 - 54));
     assert_eq!(big_num.to_f64(), Some(f64::MAX));
-    assert_eq!((&big_num + 1u8).to_f64(), None);
+    assert_eq!((&big_num + 1u8).to_f64(), Some(f64::INFINITY));
     assert_eq!((-&big_num).to_f64(), Some(f64::MIN));
-    assert_eq!(((-&big_num) - 1u8).to_f64(), None);
+    assert_eq!(((-&big_num) - 1u8).to_f64(), Some(f64::NEG_INFINITY));
 
-    assert_eq!(((BigInt::one() << 1024u16) - 1u8).to_f64(), None);
-    assert_eq!((BigInt::one() << 1024u16).to_f64(), None);
-    assert_eq!((-((BigInt::one() << 1024u16) - 1u8)).to_f64(), None);
-    assert_eq!((-(BigInt::one() << 1024u16)).to_f64(), None);
+    assert_eq!(
+        ((BigInt::one() << 1024u16) - 1u8).to_f64(),
+        Some(f64::INFINITY)
+    );
+    assert_eq!((BigInt::one() << 1024u16).to_f64(), Some(f64::INFINITY));
+    assert_eq!(
+        (-((BigInt::one() << 1024u16) - 1u8)).to_f64(),
+        Some(f64::NEG_INFINITY)
+    );
+    assert_eq!(
+        (-(BigInt::one() << 1024u16)).to_f64(),
+        Some(f64::NEG_INFINITY)
+    );
 }
 
 #[test]

tests/biguint.rs

@@ -673,10 +673,13 @@ fn test_convert_f32() {
     // largest BigUint that will round to a finite f32 value
     let big_num = (BigUint::one() << 128u8) - 1u8 - (BigUint::one() << (128u8 - 25));
     assert_eq!(big_num.to_f32(), Some(f32::MAX));
-    assert_eq!((big_num + 1u8).to_f32(), None);
+    assert_eq!((big_num + 1u8).to_f32(), Some(f32::INFINITY));
 
-    assert_eq!(((BigUint::one() << 128u8) - 1u8).to_f32(), None);
-    assert_eq!((BigUint::one() << 128u8).to_f32(), None);
+    assert_eq!(
+        ((BigUint::one() << 128u8) - 1u8).to_f32(),
+        Some(f32::INFINITY)
+    );
+    assert_eq!((BigUint::one() << 128u8).to_f32(), Some(f32::INFINITY));
 }
 
 #[test]
@@ -746,10 +749,13 @@ fn test_convert_f64() {
     // largest BigUint that will round to a finite f64 value
     let big_num = (BigUint::one() << 1024u16) - 1u8 - (BigUint::one() << (1024u16 - 54));
     assert_eq!(big_num.to_f64(), Some(f64::MAX));
-    assert_eq!((big_num + 1u8).to_f64(), None);
+    assert_eq!((big_num + 1u8).to_f64(), Some(f64::INFINITY));
 
-    assert_eq!(((BigUint::one() << 1024u16) - 1u8).to_f64(), None);
-    assert_eq!((BigUint::one() << 1024u16).to_f64(), None);
+    assert_eq!(
+        ((BigUint::one() << 1024u16) - 1u8).to_f64(),
+        Some(f64::INFINITY)
+    );
+    assert_eq!((BigUint::one() << 1024u16).to_f64(), Some(f64::INFINITY));
 }
 
 #[test]