paths and segments are now factories instead

the factory/instance deliniation is not clean but it _is_ efficient.

vacuum_gambit.p8

@@ -686,15 +686,28 @@ segment = mknew{
  --  figure out approach/depart
  -- [1..n]: destinations
  init = function(x)
-  x.remain = x.limit
+  x.init = segment.reset
+  mknew(x)
+  if not x.mirror then
+   local mirrored = {mirror=x}
+   for i, v in ipairs(x) do
+    mirrored[i] = destination.new{
+     anchor_frac=v.anchor_frac
+     accel_frac=v.accel_frac
+     x_off_frac=-v.x_off_frac
+     y_off_frac=v.y_off_frac
+    }
+   end
+   x.mirror = x.new(mirrored)
+  end
  end
 }
 
 function segment:reset()
  self.current_idx = 1
  self.remain = self.limit
- self.prev_x = nil
- self.prev_y = nil
+ self.prev_x = false
+ self.prev_y = false
  self.was_approaching = false
 end
 
@@ -745,12 +758,29 @@ end
 
 path = mknew {
  loop_idx = 1,
- current_idx = 1,
  -- [1..n]: destinations
+ init=function(x)
+  if not x.mirror then
+   local mirrored = {
+    mirror = x,
+    loop_idx = x.loop_idx
+   }
+   for i, v in ipairs(x) do
+    mirrored[i]=v.mirror
+   end
+   x.mirror = path.new(mirrored)
+  end
+  x.init = function(y)
+   for i, v in ipairs(x) do
+    y[i]=v.new{}
+   end
+   y:reset()
+  end
+  mknew(x)
+ end,
 }
 
 function path:reset()
- self.loop_idx = 1
  self.current_idx = 1
 end