bench: fix nbody bugs, r=burningtree.

src/test/bench/shootout-nbody.rs

@@ -24,10 +24,13 @@ fn main() {
         args
     };
     let n = int::from_str(args[1]).get();
-    let bodies: ~[Body::props] = NBodySystem::make();
-    io::println(fmt!("%f", NBodySystem::energy(copy bodies)));
+    let mut bodies: ~[Body::props] = NBodySystem::make();
+    io::println(fmt!("%f", NBodySystem::energy(bodies)));
     let mut i = 0;
-    while i < n { NBodySystem::advance(bodies, 0.01); i += 1; }
+    while i < n {
+        NBodySystem::advance(bodies, 0.01);
+        i += 1;
+    }
     io::println(fmt!("%f", NBodySystem::energy(bodies)));
 }
 
@@ -35,8 +38,11 @@ mod NBodySystem {
     #[legacy_exports];
 
     fn make() -> ~[Body::props] {
-        let bodies: ~[Body::props] =
-            ~[Body::sun(), Body::jupiter(), Body::saturn(), Body::uranus(),
+        let mut bodies: ~[Body::props] =
+            ~[Body::sun(),
+              Body::jupiter(),
+              Body::saturn(),
+              Body::uranus(),
               Body::neptune()];
 
         let mut px = 0.0;
@@ -53,26 +59,35 @@ mod NBodySystem {
         }
 
         // side-effecting
-        Body::offset_momentum(bodies[0], px, py, pz);
+        Body::offset_momentum(&mut bodies[0], px, py, pz);
 
         return bodies;
     }
 
-    fn advance(bodies: ~[Body::props], dt: float) {
+    fn advance(bodies: &mut [Body::props], dt: float) {
 
         let mut i = 0;
         while i < 5 {
             let mut j = i + 1;
-            while j < 5 { advance_one(bodies[i], bodies[j], dt); j += 1; }
+            while j < 5 {
+                advance_one(&mut bodies[i],
+                            &mut bodies[j], dt);
+                j += 1;
+            }
 
             i += 1;
         }
 
         i = 0;
-        while i < 5 { move_(bodies[i], dt); i += 1; }
+        while i < 5 {
+            move_(&mut bodies[i], dt);
+            i += 1;
+        }
     }
 
-    fn advance_one(bi: Body::props, bj: Body::props, dt: float) unsafe {
+    fn advance_one(bi: &mut Body::props,
+                   bj: &mut Body::props,
+                   dt: float) unsafe {
         let dx = bi.x - bj.x;
         let dy = bi.y - bj.y;
         let dz = bi.z - bj.z;
@@ -91,13 +106,13 @@ mod NBodySystem {
         bj.vz += dz * bi.mass * mag;
     }
 
-    fn move_(b: Body::props, dt: float) {
+    fn move_(b: &mut Body::props, dt: float) {
         b.x += dt * b.vx;
         b.y += dt * b.vy;
         b.z += dt * b.vz;
     }
 
-    fn energy(bodies: ~[Body::props]) -> float unsafe {
+    fn energy(bodies: &[Body::props]) -> float unsafe {
         let mut dx;
         let mut dy;
         let mut dz;
@@ -197,7 +212,8 @@ mod Body {
              mass: SOLAR_MASS};
     }
 
-    fn offset_momentum(props: Body::props, px: float, py: float, pz: float) {
+    fn offset_momentum(props: &mut Body::props,
+                       px: float, py: float, pz: float) {
         props.vx = -px / SOLAR_MASS;
         props.vy = -py / SOLAR_MASS;
         props.vz = -pz / SOLAR_MASS;