add a bunch more rand::rng extension methods - one for each primitive type and also some choose/shuffle functions (for https://github.com/mozilla/rust/issues/2379)

src/libcore/rand.rs

@@ -1,6 +1,6 @@
 #[doc = "Random number generation"];
 
-export rng, extensions;
+export rng, weighted, extensions;
 
 enum rctx {}
 
@@ -17,19 +17,123 @@ iface rng {
     fn next() -> u32;
 }
 
+#[doc = "A value with a particular weight compared to other values"]
+type weighted<T> = { weight: uint, item: T };
+
 #[doc = "Extension methods for random number generators"]
 impl extensions for rng {
 
-    #[doc = "Return a random float"]
-    fn gen_float() -> float {
-          let u1 = self.next() as float;
-          let u2 = self.next() as float;
-          let u3 = self.next() as float;
-          let scale = u32::max_value as float;
-          ret ((u1 / scale + u2) / scale + u3) / scale;
+    #[doc = "Return a random int"]
+    fn gen_int() -> int {
+        self.gen_i64() as int
     }
 
-    #[doc = "Return a random string composed of A-Z, a-z, 0-9."]
+    #[doc = "Return an int randomly chosen from the range [start, end], \
+             failing if start > end"]
+    fn gen_int_from(start: int, end: int) -> int {
+        assert start <= end;
+        start + int::abs(self.gen_int() % (end - start + 1))
+    }
+
+    #[doc = "Return a random i8"]
+    fn gen_i8() -> i8 {
+        self.next() as i8
+    }
+
+    #[doc = "Return a random i16"]
+    fn gen_i16() -> i16 {
+        self.next() as i16
+    }
+
+    #[doc = "Return a random i32"]
+    fn gen_i32() -> i32 {
+        self.next() as i32
+    }
+
+    #[doc = "Return a random i64"]
+    fn gen_i64() -> i64 {
+        (self.next() as i64 << 32) | self.next() as i64
+    }
+
+    #[doc = "Return a random uint"]
+    fn gen_uint() -> uint {
+        self.gen_u64() as u64
+    }
+
+    #[doc = "Return a uint randomly chosen from the range [start, end], \
+             failing if start > end"]
+    fn gen_uint_from(start: uint, end: uint) -> uint {
+        assert start <= end;
+        start + (self.gen_uint() % (end - start + 1u))
+    }
+
+    #[doc = "Return a random u8"]
+    fn gen_u8() -> u8 {
+        self.next() as u8
+    }
+
+    #[doc = "Return a random u16"]
+    fn gen_u16() -> u16 {
+        self.next() as u16
+    }
+
+    #[doc = "Return a random u32"]
+    fn gen_u32() -> u32 {
+        self.next()
+    }
+
+    #[doc = "Return a random u64"]
+    fn gen_u64() -> u64 {
+        (self.next() as u64 << 32) | self.next() as u64
+    }
+
+    #[doc = "Return a random float"]
+    fn gen_float() -> float {
+        self.gen_f64() as float
+    }
+
+    #[doc = "Return a random f32"]
+    fn gen_f32() -> f32 {
+        self.gen_f64() as f32
+    }
+
+    #[doc = "Return a random f64"]
+    fn gen_f64() -> f64 {
+        let u1 = self.next() as f64;
+        let u2 = self.next() as f64;
+        let u3 = self.next() as f64;
+        let scale = u32::max_value as f64;
+        ret ((u1 / scale + u2) / scale + u3) / scale;
+    }
+
+    #[doc = "Return a random char"]
+    fn gen_char() -> char {
+        self.next() as char
+    }
+
+    #[doc = "Return a char randomly chosen from chars, failing if chars is \
+             empty"]
+    fn gen_char_from(chars: str) -> char {
+        assert !chars.is_empty();
+        self.choose(str::chars(chars))
+    }
+
+    #[doc = "Return a random bool"]
+    fn gen_bool() -> bool {
+        self.next() & 1u32 == 1u32
+    }
+
+    #[doc = "Return a bool with a 1 in n chance of true"]
+    fn gen_weighted_bool(n: uint) -> bool {
+        if n == 0u {
+            true
+        } else {
+            self.gen_uint_from(1u, n) == 1u
+        }
+    }
+
+    #[doc = "Return a random string of the specified length composed of A-Z, \
+             a-z, 0-9"]
     fn gen_str(len: uint) -> str {
         let charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
                       "abcdefghijklmnopqrstuvwxyz" +
@@ -37,24 +141,90 @@ impl extensions for rng {
         let mut s = "";
         let mut i = 0u;
         while (i < len) {
-            let n = self.next() as uint % charset.len();
-            s = s + str::from_char(str::char_at(charset, n));
+            s = s + str::from_char(self.gen_char_from(charset));
             i += 1u;
         }
         s
     }
 
-    #[doc = "Return a random byte string."]
+    #[doc = "Return a random byte string of the specified length"]
     fn gen_bytes(len: uint) -> [u8] {
-        let mut v = [];
-        let mut i = 0u;
-        while i < len {
-            let n = self.next() as uint;
-            v += [(n % (u8::max_value as uint)) as u8];
-            i += 1u;
+        vec::from_fn(len) {|_i|
+            self.gen_u8()
         }
-        v
     }
+
+    #[doc = "Choose an item randomly, failing if values is empty"]
+    fn choose<T:copy>(values: [T]) -> T {
+        self.choose_option(values).get()
+    }
+
+    #[doc = "Choose some(item) randomly, returning none if values is empty"]
+    fn choose_option<T:copy>(values: [T]) -> option<T> {
+        if values.is_empty() {
+            none
+        } else {
+            some(values[self.gen_uint_from(0u, values.len() - 1u)])
+        }
+    }
+
+    #[doc = "Choose an item respecting the relative weights, failing if \
+             the sum of the weights is 0"]
+    fn choose_weighted<T: copy>(v : [weighted<T>]) -> T {
+        self.choose_weighted_option(v).get()
+    }
+
+    #[doc = "Choose some(item) respecting the relative weights, returning \
+             none if the sum of the weights is 0"]
+    fn choose_weighted_option<T:copy>(v: [weighted<T>]) -> option<T> {
+        let mut total = 0u;
+        for v.each {|item|
+            total += item.weight;
+        }
+        if total == 0u {
+            ret none;
+        }
+        let chosen = self.gen_uint_from(0u, total - 1u);
+        let mut so_far = 0u;
+        for v.each {|item|
+            so_far += item.weight;
+            if so_far > chosen {
+                ret some(item.item);
+            }
+        }
+        unreachable();
+    }
+
+    #[doc = "Return a vec containing copies of the items, in order, where \
+             the weight of the item determines how many copies there are"]
+    fn weighted_vec<T:copy>(v: [weighted<T>]) -> [T] {
+        let mut r = [];
+        for v.each {|item|
+            uint::range(0u, item.weight) {|_i|
+                r += [item.item];
+            }
+        }
+        r
+    }
+
+    #[doc = "Shuffle a vec"]
+    fn shuffle<T:copy>(values: [T]) -> [T] {
+        let mut m = vec::to_mut(values);
+        self.shuffle_mut(m);
+        ret vec::from_mut(m);
+    }
+
+    #[doc = "Shuffle a mutable vec in place"]
+    fn shuffle_mut<T>(&values: [mut T]) {
+        let mut i = values.len();
+        while i >= 2u {
+            // invariant: elements with index >= i have been locked in place.
+            i -= 1u;
+            // lock element i in place.
+            vec::swap(values, i, self.gen_uint_from(0u, i));
+        }
+    }
+
 }
 
 #[doc = "Create a random number generator"]
@@ -72,27 +242,33 @@ fn rng() -> rng {
 mod tests {
 
     #[test]
-    fn test() {
-        let r1 = rand::rng();
-        log(debug, r1.next());
-        log(debug, r1.next());
-        {
-            let r2 = rand::rng();
-            log(debug, r1.next());
-            log(debug, r2.next());
-            log(debug, r1.next());
-            log(debug, r1.next());
-            log(debug, r2.next());
-            log(debug, r2.next());
-            log(debug, r1.next());
-            log(debug, r1.next());
-            log(debug, r1.next());
-            log(debug, r2.next());
-            log(debug, r2.next());
-            log(debug, r2.next());
-        }
-        log(debug, r1.next());
-        log(debug, r1.next());
+    fn gen_int_from() {
+        let r = rand::rng();
+        let a = r.gen_int_from(-3, 42);
+        assert a >= -3 && a <= 42;
+        assert r.gen_int_from(0, 0) == 0;
+        assert r.gen_int_from(-12, -12) == -12;
+    }
+
+    #[test]
+    #[should_fail]
+    fn gen_int_from_fail() {
+        rand::rng().gen_int_from(5, -2);
+    }
+
+    #[test]
+    fn gen_uint_from() {
+        let r = rand::rng();
+        let a = r.gen_uint_from(3u, 42u);
+        assert a >= 3u && a <= 42u;
+        assert r.gen_uint_from(0u, 0u) == 0u;
+        assert r.gen_uint_from(12u, 12u) == 12u;
+    }
+
+    #[test]
+    #[should_fail]
+    fn gen_uint_from_fail() {
+        rand::rng().gen_uint_from(5u, 2u);
     }
 
     #[test]
@@ -103,6 +279,13 @@ mod tests {
         log(debug, (a, b));
     }
 
+    #[test]
+    fn gen_weighted_bool() {
+        let r = rand::rng();
+        assert r.gen_weighted_bool(0u) == true;
+        assert r.gen_weighted_bool(1u) == true;
+    }
+
     #[test]
     fn gen_str() {
         let r = rand::rng();
@@ -121,6 +304,60 @@ mod tests {
         assert r.gen_bytes(10u).len() == 10u;
         assert r.gen_bytes(16u).len() == 16u;
     }
+
+    #[test]
+    fn choose() {
+        let r = rand::rng();
+        assert r.choose([1, 1, 1]) == 1;
+    }
+
+    #[test]
+    fn choose_option() {
+        let r = rand::rng();
+        assert r.choose_option([]) == none::<int>;
+        assert r.choose_option([1, 1, 1]) == some(1);
+    }
+
+    #[test]
+    fn choose_weighted() {
+        let r = rand::rng();
+        assert r.choose_weighted([{weight: 1u, item: 42}]) == 42;
+        assert r.choose_weighted([
+            {weight: 0u, item: 42},
+            {weight: 1u, item: 43}
+        ]) == 43;
+    }
+
+    #[test]
+    fn choose_weighted_option() {
+        let r = rand::rng();
+        assert r.choose_weighted_option([{weight: 1u, item: 42}]) == some(42);
+        assert r.choose_weighted_option([
+            {weight: 0u, item: 42},
+            {weight: 1u, item: 43}
+        ]) == some(43);
+        assert r.choose_weighted_option([]) == none::<int>;
+    }
+
+    #[test]
+    fn weighted_vec() {
+        let r = rand::rng();
+        let empty: [int] = [];
+        assert r.weighted_vec([]) == empty;
+        assert r.weighted_vec([
+            {weight: 0u, item: 3u},
+            {weight: 1u, item: 2u},
+            {weight: 2u, item: 1u}
+        ]) == [2u, 1u, 1u];
+    }
+
+    #[test]
+    fn shuffle() {
+        let r = rand::rng();
+        let empty: [int] = [];
+        assert r.shuffle([]) == empty;
+        assert r.shuffle([1, 1, 1]) == [1, 1, 1];
+    }
 }