fix eternal horizontal bullets

The only use of a collider is intertwined with the ship list, so I can combine the "prepare to yoink" and "populate collider" and "iterate list" steps, and I can combine the "hide" and "yoink" steps. This doesn't save tokens now but it's about to, when I use the eship collider to test pship collision.

vacuum_gambit.p8

@@ -60,7 +60,7 @@ function mknew(tt)
 end
 
 -- intrusive singly-linked list.
--- cannot be nested!
+-- cannot be nested or crossed!
 linked_list = mknew{
  is_linked_list=true,
  init = function(x)
@@ -93,9 +93,7 @@ end
 
 -- strip calls f(x) for each
 -- node, removing each node for
--- which f(x) returns true. it
+-- which f(x) returns true.
--- returns the new tail; nil
--- if the list is now empty.
 function linked_list:strip(f)
  local p, n = self, self.next
  while n do
@@ -107,7 +105,6 @@ function linked_list:strip(f)
   n = n.next
  end
  self.tail = p
- return p
 end
 
 -- optimized special case -
@@ -237,52 +234,38 @@ function updategame()
  end
  events:vore(new_events)
  events:strip(call_move)
- for _, lst in ipairs{intangibles_bg, eships, pbullets, ebullets} do
+ for _, lst in ipairs{intangibles_bg, eships, pbullets} do
   lst:strip(call_move)
  end
 
+	-- eship collider will be used
+ -- both for pship and pbullets.
+ local eship_collider = collider.new{from=eships}
+
  if not ps.dead then
   ps:move()
   local pbox = hurtbox(ps)
-  eships:strip(function(es)
+  for es in eship_collider:iterate_collisions(pbox) do
-   if(not collides(pbox, hurtbox(es))) return
    ps:hitship(es)
-   return es:hitship(ps)
+   if(es:hitship(ps)) eship_collider:yoink(es)
-  end)
+  end
   ebullets:strip(function(eb)
+   -- loopify this when split moves implemented
+   if (eb:move()) return true
    if (not collides(pbox, hurtbox(eb))) return
    ps:hitbullet(eb)
    return eb:hitship(ps)
   end)
+ else
+  ebullets:strip(call_move)
  end
 
-	-- many bullets and many enemy ships;
+ pbullets:strip(function(pb)
-	-- use bucket collider for efficiency
+  for es in eship_collider:iterate_collisions(hurtbox(pb)) do
- local pbullet_collider = collider.new()
+   if (es:hitbullet(pb)) eship_collider:yoink(es)
- local p, n = pbullets, pbullets.next
+   if (pb:hitship(es)) return true
- while n do
-  n.prev = p
-  pbullet_collider:insert(n)
-  p = n
-  n = p.next
- end
-
- eships:strip(
-  function(es)
-   for pb in all(pbullet_collider:get_collisions(es)) do
-    if pb:hitship(es) then
-     pbullet_collider:hide(pb)
-     pb.prev.next = pb.next
-     if pb.next then
-      pb.next.prev = pb.prev
-     else
-      pbullets.tail = pb.prev
-     end
-    end
-    if (es:hitbullet(pb)) return true
-   end
   end
- )
+ end)
  
  intangibles_fg:strip(call_move)
 
@@ -837,7 +820,7 @@ function bullet_base:move()
  self.x += self.dx
  self.y += self.dy
  if (self.f) self.f -= 1
- if (self.y > 145) or (self.y < -8 * self.height) or (self.f and self.f < 0) then
+ if (self.y > 145) or (self.y < -64) or (self.f and self.f < 0) or (self.x > 256) or (self.x < -128) then
   self:die()
   return true
  end
@@ -1445,6 +1428,22 @@ end
 collider = mknew{
  init = function(x)
   x.suppress = {}
+  local p, n = x.from, x.from.next
+  while n do
+   -- insert
+   for i in all(collider_indexes(hurtbox(n))) do
+    local a = x[i]
+    if not a then
+     a = {}
+     x[i] = a
+    end
+    add(a, n)
+   end
+   -- prepare yoink
+   n.prev = p
+   p = n
+   n = n.next
+  end
  end,
 }
 
@@ -1458,40 +1457,39 @@ function collider_indexes(box)
  return ret
 end
 
-function collider:insert(item)
+function collider:yoink(item)
- -- todo: separate "big items" list?
- local bdx = collider_indexes(hurtbox(item))
- for i in all(bdx) do
-  local x = self[i]
-  if not x then
-   x = {}
-   self[i] = x
-  end
-  add(x, item)
- end
-end
-
-function collider:hide(item)
  self.suppress[item]=true
+ local p,n = item.prev,item.next
+ p.next = n
+ if n then
+  n.prev = p
+ else
+  self.from.tail = p
+ end
 end
 
-function collider:get_collisions(item)
+function collider:iterate_collisions(box)
- local found = { }
  local seen = { }
- local box = hurtbox(item)
  local bucket_ids = collider_indexes(box)
- for b_idx in all(bucket_ids) do
+ local bii, bidl, bucket, bi, blen = 1, #bucket_ids, false, 1, 0
-  local bucket = self[b_idx]
+ return function()
-  if bucket then
+  while bii <= bidl do
-   for candidate in all(bucket) do
+   if not bucket then
-    if not (seen[candidate] or self.suppress[candidate]) then
+    bucket,blen = self[bucket_ids[bii]],0
-     seen[candidate] = true
+    if (bucket) blen=#bucket
-     if (collides(box, hurtbox(candidate))) add(found, candidate)
-    end
    end
+   while bi <= blen do
+    local candidate = bucket[bi]
+    bi += 1
+    if not seen[candidate] then
+     seen[candidate] = true
+     if (not self.suppress[candidate] and collides(box, hurtbox(candidate))) return candidate
+    end
+   end -- done with this bucket
+   bi=1
+   bii += 1
   end
- end
+ end -- end of closure def
- return found
 end
 
 -->8