Document results of non-positive logarithms

Author: syvb

library/std/src/f128.rs

@@ -468,6 +468,8 @@ impl f128 {
 
     /// Returns the natural logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,
@@ -499,6 +501,8 @@ impl f128 {
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// The result might not be correctly rounded owing to implementation details;
     /// `self.log2()` can produce more accurate results for base 2, and
     /// `self.log10()` can produce more accurate results for base 10.
@@ -532,6 +536,8 @@ impl f128 {
 
     /// Returns the base 2 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,
@@ -561,6 +567,8 @@ impl f128 {
 
     /// Returns the base 10 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,

library/std/src/f16.rs

@@ -468,6 +468,8 @@ impl f16 {
 
     /// Returns the natural logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,
@@ -499,6 +501,8 @@ impl f16 {
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// The result might not be correctly rounded owing to implementation details;
     /// `self.log2()` can produce more accurate results for base 2, and
     /// `self.log10()` can produce more accurate results for base 10.
@@ -532,6 +536,8 @@ impl f16 {
 
     /// Returns the base 2 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,
@@ -561,6 +567,8 @@ impl f16 {
 
     /// Returns the base 10 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,

library/std/src/f32.rs

@@ -424,6 +424,8 @@ impl f32 {
 
     /// Returns the natural logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
@@ -451,6 +453,8 @@ impl f32 {
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// The result might not be correctly rounded owing to implementation details;
     /// `self.log2()` can produce more accurate results for base 2, and
     /// `self.log10()` can produce more accurate results for base 10.
@@ -480,6 +484,8 @@ impl f32 {
 
     /// Returns the base 2 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
@@ -505,6 +511,8 @@ impl f32 {
 
     /// Returns the base 10 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and

library/std/src/f64.rs

@@ -424,6 +424,8 @@ impl f64 {
 
     /// Returns the natural logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
@@ -451,6 +453,8 @@ impl f64 {
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// The result might not be correctly rounded owing to implementation details;
     /// `self.log2()` can produce more accurate results for base 2, and
     /// `self.log10()` can produce more accurate results for base 10.
@@ -480,6 +484,8 @@ impl f64 {
 
     /// Returns the base 2 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
@@ -505,6 +511,8 @@ impl f64 {
 
     /// Returns the base 10 logarithm of the number.
     ///
+    /// This returns NaN when the number is negative, and negative infinity when number is zero.
+    ///
     /// # Unspecified precision
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and