Rollup merge of rust-lang#140150 - RalfJung:MAX_EXP, r=tgross35

fix MAX_EXP and MIN_EXP docs

As pointed out in rust-lang#88734, the docs for these constants are wrong.

r? ``@tgross35``

Author: matthiaskrgr

core/src/num/f128.rs

@@ -197,16 +197,22 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     pub const MAX: f128 = 1.18973149535723176508575932662800702e+4932_f128;
 
-    /// One greater than the minimum possible normal power of 2 exponent.
+    /// One greater than the minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MIN_EXP`, then normal numbers
-    /// ≥&nbsp;0.5&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all normal numbers representable by this type are
+    /// greater than or equal to 0.5&nbsp;×&nbsp;2<sup><i>MIN_EXP</i></sup>.
     #[unstable(feature = "f128", issue = "116909")]
     pub const MIN_EXP: i32 = -16_381;
-    /// Maximum possible power of 2 exponent.
+    /// One greater than the maximum possible power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MAX_EXP`, then normal numbers
-    /// &lt;&nbsp;1&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact maximum possible power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all numbers representable by this type are
+    /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
     #[unstable(feature = "f128", issue = "116909")]
     pub const MAX_EXP: i32 = 16_384;
 

core/src/num/f16.rs

@@ -192,16 +192,22 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     pub const MAX: f16 = 6.5504e+4_f16;
 
-    /// One greater than the minimum possible normal power of 2 exponent.
+    /// One greater than the minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MIN_EXP`, then normal numbers
-    /// ≥&nbsp;0.5&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all normal numbers representable by this type are
+    /// greater than or equal to 0.5&nbsp;×&nbsp;2<sup><i>MIN_EXP</i></sup>.
     #[unstable(feature = "f16", issue = "116909")]
     pub const MIN_EXP: i32 = -13;
-    /// Maximum possible power of 2 exponent.
+    /// One greater than the maximum possible power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MAX_EXP`, then normal numbers
-    /// &lt;&nbsp;1&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact maximum possible power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all numbers representable by this type are
+    /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
     #[unstable(feature = "f16", issue = "116909")]
     pub const MAX_EXP: i32 = 16;
 

core/src/num/f32.rs

@@ -443,16 +443,22 @@ impl f32 {
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MAX: f32 = 3.40282347e+38_f32;
 
-    /// One greater than the minimum possible normal power of 2 exponent.
+    /// One greater than the minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MIN_EXP`, then normal numbers
-    /// ≥&nbsp;0.5&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all normal numbers representable by this type are
+    /// greater than or equal to 0.5&nbsp;×&nbsp;2<sup><i>MIN_EXP</i></sup>.
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MIN_EXP: i32 = -125;
-    /// Maximum possible power of 2 exponent.
+    /// One greater than the maximum possible power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MAX_EXP`, then normal numbers
-    /// &lt;&nbsp;1&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact maximum possible power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all numbers representable by this type are
+    /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MAX_EXP: i32 = 128;
 

core/src/num/f64.rs

@@ -442,16 +442,22 @@ impl f64 {
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MAX: f64 = 1.7976931348623157e+308_f64;
 
-    /// One greater than the minimum possible normal power of 2 exponent.
+    /// One greater than the minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MIN_EXP`, then normal numbers
-    /// ≥&nbsp;0.5&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact minimum possible *normal* power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all normal numbers representable by this type are
+    /// greater than or equal to 0.5&nbsp;×&nbsp;2<sup><i>MIN_EXP</i></sup>.
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MIN_EXP: i32 = -1021;
-    /// Maximum possible power of 2 exponent.
+    /// One greater than the maximum possible power of 2 exponent
+    /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
     ///
-    /// If <i>x</i>&nbsp;=&nbsp;`MAX_EXP`, then normal numbers
-    /// &lt;&nbsp;1&nbsp;×&nbsp;2<sup><i>x</i></sup>.
+    /// This corresponds to the exact maximum possible power of 2 exponent
+    /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
+    /// In other words, all numbers representable by this type are
+    /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MAX_EXP: i32 = 1024;