Update position and speed of all bodies

src/Lib.hs

@@ -70,6 +70,16 @@ update dt (Body m pos speed) neighbours =
         newspeed = speed + dt *^ accel
         newpos = pos + dt *^ P newspeed
 
+-- Update all bodies with a timestep dt
+updateAll :: Double -> [Body] -> [Body]
+updateAll dt bodies = aux [] [] bodies
+  where
+    -- Cycles through all bodies, updates each one and stores it in
+    -- res. Each body already updated is moved to prev.
+    aux res prev [] = res
+    aux res prev (b:next) =
+          aux (newb:res) (b:prev) next
+          where newb = update dt b $ prev ++ next
                     
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 -- EXAMPLES