auto merge of #9810 : huonw/rust/rand3, r=alexcrichton

- Adds the `Sample` and `IndependentSample` traits for generating numbers where there are parameters (e.g. a list of elements to draw from, or the mean/variance of a normal distribution). The former takes `&mut self` and the latter takes `&self` (this is the only difference).
- Adds proper `Normal` and `Exp`-onential distributions
- Adds `Range` which generates `[lo, hi)` generically & properly (via a new trait) replacing the incorrect behaviour of `Rng.gen_integer_range` (this has become `Rng.gen_range` for convenience, it's far more efficient to use `Range` itself)
- Move the `Weighted` struct from `std::rand` to `std::rand::distributions` & improve it
- optimisations and docs

Author: bors

src/libextra/base64.rs

@@ -318,7 +318,7 @@ mod test {
         use std::vec;
 
         do 1000.times {
-            let times = task_rng().gen_integer_range(1u, 100);
+            let times = task_rng().gen_range(1u, 100);
             let v = vec::from_fn(times, |_| random::<u8>());
             assert_eq!(v.to_base64(STANDARD).from_base64().unwrap(), v);
         }

src/libextra/crypto/cryptoutil.rs

@@ -365,7 +365,7 @@ pub mod test {
         digest.reset();
 
         while count < total_size {
-            let next: uint = rng.gen_integer_range(0, 2 * blocksize + 1);
+            let next: uint = rng.gen_range(0, 2 * blocksize + 1);
             let remaining = total_size - count;
             let size = if next > remaining { remaining } else { next };
             digest.input(buffer.slice_to(size));

src/libextra/flate.rs

@@ -113,7 +113,7 @@ mod tests {
         let mut r = rand::rng();
         let mut words = ~[];
         do 20.times {
-            let range = r.gen_integer_range(1u, 10);
+            let range = r.gen_range(1u, 10);
             words.push(r.gen_vec::<u8>(range));
         }
         do 20.times {

src/libextra/sort.rs

@@ -1069,8 +1069,8 @@ mod big_tests {
             isSorted(arr);
 
             do 3.times {
-                let i1 = rng.gen_integer_range(0u, n);
-                let i2 = rng.gen_integer_range(0u, n);
+                let i1 = rng.gen_range(0u, n);
+                let i2 = rng.gen_range(0u, n);
                 arr.swap(i1, i2);
             }
             tim_sort(arr); // 3sort
@@ -1088,7 +1088,7 @@ mod big_tests {
             isSorted(arr);
 
             do (n/100).times {
-                let idx = rng.gen_integer_range(0u, n);
+                let idx = rng.gen_range(0u, n);
                 arr[idx] = rng.gen();
             }
             tim_sort(arr);
@@ -1141,8 +1141,8 @@ mod big_tests {
             isSorted(arr);
 
             do 3.times {
-                let i1 = rng.gen_integer_range(0u, n);
-                let i2 = rng.gen_integer_range(0u, n);
+                let i1 = rng.gen_range(0u, n);
+                let i2 = rng.gen_range(0u, n);
                 arr.swap(i1, i2);
             }
             tim_sort(arr); // 3sort
@@ -1160,7 +1160,7 @@ mod big_tests {
             isSorted(arr);
 
             do (n/100).times {
-                let idx = rng.gen_integer_range(0u, n);
+                let idx = rng.gen_range(0u, n);
                 arr[idx] = @rng.gen();
             }
             tim_sort(arr);

src/libextra/treemap.rs

@@ -1028,7 +1028,7 @@ mod test_treemap {
             }
 
             do 30.times {
-                let r = rng.gen_integer_range(0, ctrl.len());
+                let r = rng.gen_range(0, ctrl.len());
                 let (key, _) = ctrl.remove(r);
                 assert!(map.remove(&key));
                 check_structure(&map);