Add gen_bool method to Rng

Author: pitdicker

src/lib.rs

@@ -537,6 +537,21 @@ pub trait Rng: RngCore {
         n <= 1 || self.gen_range(0, n) == 0
     }
 
+    /// Return a bool with a `p` probability of being true.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use rand::{thread_rng, Rng};
+    ///
+    /// let mut rng = thread_rng();
+    /// println!("{}", rng.gen_bool(1.0 / 3.0));
+    /// ```
+    fn gen_bool(&mut self, p: f64) -> bool {
+        assert!(p >= 0.0 && p <= 1.0);
+        self.sample::<f64, _>(distributions::HighPrecision01) < p
+    }
+
     /// Return an iterator of random characters from the set A-Z,a-z,0-9.
     ///
     /// # Example