Misc golf and perf improvements

chameleonic.p8

@@ -117,7 +117,7 @@ function _rast(
  if (x0<x1) sx=1
  if (y0<y1) sy=1
 	
- local done=false,err
+ local done,err
  if dx>dy then
   err=dx/2.0
   while x0!=x1 do
@@ -234,10 +234,10 @@ function level:reinit(n)
  self.ix=n
  self.todo={}
  self.bigx,self.bigy=n%8,n\8
+ self.dirty=false
 
  self:load_dynobjs()
- self:recollide()
- self:reanchor(true)
+ self:recollide_reanchor()
  self:spawn_exit()
 end
 
@@ -252,8 +252,7 @@ end
 normpal = {[1]=0,[8]=0,[14]=0}
 pitpal = {[8]=0,[13]=3,[4]=3,[7]=3}
 function level:draw()
- fillp(0b1111111110111111)
- rectfill(0,0,127,127,0x55)
+ cls(5)
  fillp()
  pal(normpal)
  map(
@@ -289,7 +288,7 @@ function level:busy()
  for _,crate in pairs(self._crates) do
   if (#crate.todo>0) return true 
  end
- return false
+ return 
 end
 
 function level:update()
@@ -310,10 +309,12 @@ function level:update()
  end
  for cix in all(remove) do
   self._crates[cix]=nil
+  self.dirty=true
  end
- if #remove>0 then
-  self:recollide()
-  self:reanchor()
+
+ if self.dirty then
+  self:recollide_reanchor()
+  self.dirty=false
  end
 end
 
@@ -345,19 +346,17 @@ function level:load_dynobjs()
  end
 end
 
-function level:recollide()
+function level:recollide_reanchor()
  self._coll={}
  for mx=0,15 do
   for my=0,15 do
    local mxy=_mix(mx,my)
    self._coll[mxy]=
     fget(self:_mget(mx,my),7) or
-    self._crates[mxy]!=nil
-  end
+    self._crates[mxy]
   end
  end
 
-function level:reanchor()
  local anch_new={}
  for dxy in all{{-1,-1},{1,-1},{-1,1},{1,1}} do
   local dx,dy=unpack(dxy)
@@ -390,18 +389,12 @@ function level:reanchor()
   end
  end
 
- local anch_old=self._anch
- if (anch_old==nil) anch_old={}
- for _,old in pairs(anch_old) do
-  old.dropped=true
- end
-
+ local moves={}
  for k,new in pairs(anch_new) do
-  local old=anch_old[k]
+  local old=(self._anch or {})[k]
   if old then
-   anch_new[k]=old
-   old.ax_old,old.ay_old,old.ax,old.ay,old.adx,old.ady=old.ax,old.ay,new.ax,new.ay,new.adx,new.ady
-   old.dropped=nil
+   anch_new[k]=new
+   if (old.ax!=new.ax or old.ay!=new.ay) add(moves,{old.ax,old.ay,new.ax,new.ay,old,key=k})
   end
  end
  self._anch=anch_new
@@ -410,15 +403,16 @@ function level:reanchor()
   add(self._anch_keys,{key=k})
  end
  shellsort(self._anch_keys)
- for point in self:anchor_points() do
-  if point.ax_old and player.rope and (point.ax_old != point.ax or point.ay_old != point.ay) then 
-   -- printh("moving: "..tostring({point.ax_old,point.ay_old}).."=>"..tostring({point.ax,point.ay}))
-   player.rope:be_pushed_by(point,point.ax_old,point.ay_old)
-  end
-  point.ax_old,point.ay_old=nil,nil
+ shellsort(moves)
+ --printh("!!STARTING!!")
+
+ if player.rope then
+  player.rope:experience_anchor_moves(moves)
  end
 
- if (player.rope) player.rope:relax()
+ for point in self:anchor_points() do
+  point.moved=nil
+ end
 end
 
 function level:win_at(mx,my)
@@ -426,22 +420,28 @@ function level:win_at(mx,my)
 end
 
 function level:anchor_points()
- keys=all(self._anch_keys)
+ -- TODO: Return this to using all()
+ local keys=all(self._anch_keys)
  return function() 
   local k=keys()
-  if (k==nil) return nil
-  return self._anch[k.key]
+  if (k) return self._anch[k.key]
+ end
+end
+
+function level:anchor_at(ax,ay)
+ for i in self:anchor_points() do
+  if (i.ax==ax and i.ay==ay) return i
  end
 end
 
 function level:get_open_pit(mx,my)
  local pit=self._pits[_mix(mx,my)]
- if (pit and pit.contents==nil) return pit
+ if (pit and not pit.contents) return pit
 end
 
 function level:spawn_exit()
  self._wins={}
- local spawned=false
+ local spawned
  local spawn_at=function(x,y)
   if (self:_mget(x,y)!=1) return
   assert(not spawned,x..","..y) 
@@ -470,11 +470,8 @@ function level:spawn_exit()
 end
 
 function level:mcoll(mx,my)
- return self._coll[_mix(mx,my)]!=false
-end
-
-function level:pcoll(px,py)
- return self:mcoll(px\8,py\8)
+ if ((mx | my) & 0xFFF0!=0) return true
+ return self._coll[_mix(mx,my)]
 end
 
 function level:get_crate(mx,my)
@@ -557,12 +554,12 @@ function level:can_move(
  if (is_player and self:win_at(mx1,my1)) return true 
  if (is_player and self:get_open_pit(mx1,my1)) return wrongbleep:adequately_warned()
 
- if (self:mcoll(mx1,my1) or player.x==mx1 and player.y==my1) return false
+ if (self:mcoll(mx1,my1) or player.x==mx1 and player.y==my1) return 
 
  if player.rope then
   local w,h=1.2,0.2
   if (dmx==0) w,h=0.2,1.2
-  if (player.rope:collide_mrect(mx0+ropecheck[dmx+2],my0+ropecheck[dmy+2],w,h,exclude_src,exclude_dst)) return false
+  if (player.rope:collide_mrect(mx0+ropecheck[dmx+2],my0+ropecheck[dmy+2],w,h,exclude_src,exclude_dst)) return 
  end
  
  return true
@@ -578,8 +575,7 @@ function level:tug_crate(mx0,my0,dmx,dmy)
  local px1,py1=mx1*8,my1*8
  existing.todo={
   {px=px1+dmx,py=py1+dmy,mx=mx1,my=my1,update=function()
-   self:recollide()
-   self:reanchor()
+   self.dirty=true
    return true
   end},
   {px=px1,py=py1}
@@ -604,7 +600,7 @@ function player:reinit(x,y)
  self.px,self.py=0,0
  self.todo={}
  self.cooldown=4
- self.rope=nil
+ self.rope=nil  -- don't elide, needs to be cleared if present
 
  self.fall_frame=0
  
@@ -856,9 +852,9 @@ function rope:update()
   if (self.state.frame>=3) self.state={name="latched"}
 
  elseif self.state.name=="latched" then
-  if (self.latch==nil) wrongbleep:bleep(5) self:destroy() return
+  if (not self.latch) wrongbleep:bleep(5) self:destroy() return
 
-  if self.latch and self.latch.rec then
+  if self.latch.rec then
    self:drag_src(
     self.latch.rec.mx+0.5+self.latch.ax_offset,
     self.latch.rec.my+0.5+self.latch.ay_offset
@@ -920,7 +916,7 @@ end
 
 function rope:draw(artificial_px,artificial_py)
  local points,highlight=self:_tug(true)
- local n,perc_to_show,from_end = self.state.name,1.0,false
+ local n,perc_to_show,from_end = self.state.name,1.0
  if (n=="done") return
  if (n=="cast") perc_to_show=self.state.frame/2
  if (n=="destroy") perc_to_show=(1.0-self.state.frame/4)^2
@@ -995,31 +991,26 @@ function rope:draw(artificial_px,artificial_py)
  local sy=0
  while true do
   if (n1==nil) break
+  local anch=level:anchor_at(n1.ax,n1.ay)
   local x=n1.ax*8
   local y=n1.ay*8
-  if n1.associated_with then
-   if (n1.associated_with.adx>0) x-=1
-   if (n1.associated_with.ady>0) y-=1
+  if anch then
+   if (anch.adx>0) x-=1
+   if (anch.ady>0) y-=1
   end
   rectfill(x-1,y-1,x+1,y+1,12)
   print("ax="..n1.ax..",ay="..n1.ay,72,sy)
-  print(tostring(n1.associated_with and (not n1.associated_with.dropped and n1.associated_with.ax==n1.ax and n1.associated_with.ay==n1.ay)),76,sy+7)
-  sy+=14
+  sy+=7
 
   local n0=n1.prev
   local n2=n1.next
   if n0!=nil and n2!=nil then
-   if n1.associated_with then
-    local _,_,_,adx,ady=would_stick(n0.ax,n0.ay,n1.associated_with,n2.ax,n2.ay)
-    assert(adx==-1 or adx==0 or adx==1)
-    assert(ady==-1 or ady==0 or ady==1)
-    --assert(not (adx==0 and ady==0))
+   if anch then
+    local _,_,_=would_stick(anch,n0.ax,n0.ay,n1.ax,n1.ay,n2.ax,n2.ay)
 
     local c=3
-    if (n1.associated_with.dropped) c=4
+    if (anch.dropped) c=4
     rectfill(x+2,y+2,x+4,y+4,c)
-    pset(x+adx*2,y,9)
-    pset(x,y+ady*2,9)
    else
    rectfill(x+2,y+2,x+4,y+4,2)
    end
@@ -1057,58 +1048,35 @@ function rope:drag(n1,ax_new,ay_new)
 end
 
 function rope:relax()
- local n0=self.src
- while true do
-  if (n0==nil) break
-  if n0.associated_with and n0.associated_with.dropped then
-   for i in level:anchor_points() do
-    if i.ax==n0.ax and i.ay==n0.ay then
-     n0.associated_with=i
-     break
-    end
-   end
-  end
-
-  n0=n0.next
- end
-
  local n0=self.src
  while true do
   local n1=n0.next
-  if (n1==nil) break
+  if (not n1) break
   local n2=n1.next
 
+
   if n0.ax==n1.ax and n0.ay==n1.ay then 
    n0.next=n2 
-   if (n2!=nil) n2.prev=n0
+   if (n2) n2.prev=n0
   else
    n0=n0.next
   end
  end
 
  local n0=self.src
- while true do
-  if (n0==nil) return
+ while n0 do
   local n1=n0.next
-  if (n1==nil) return
+  if (not n1) return
   local n2=n1.next
-  if (n2==nil) return
-
-  if n1.associated_with!=nil then
+  if (not n2) return
 
   local x0,y0=n0.ax,n0.ay
   local x1,y1=n1.ax,n1.ay
   local x2,y2=n2.ax,n2.ay
 
-   if x1!=n1.associated_with.ax or y1!=n1.associated_with.ay then
-    -- printh("dragging home: "..tostring{n1.ax,n1.ay}.."->"..tostring(n1.associated_with))
-    self:_drag(n1,n1.associated_with.ax,n1.associated_with.ay)
-   end
-
-   local would,x1_new,y1_new=would_stick(x0,y0,n1.associated_with,x2,y2)
+  local anch=level:anchor_at(n1.ax,n1.ay)
+  local would,x1_new,y1_new=would_stick(anch,x0,y0,x1,y1,x2,y2)
   if not would and not (n1.ax==x1_new and n1.ay==y1_new) then
-    -- printh("dragging: "..tostring{n1.associated_with, {x1_new, y1_new}})
-    -- printh("relaxing: "..tostring(n0.associated_with).."->"..tostring(n1.associated_with).."->"..tostring(n2.associated_with))
    self:_drag(n1,x1_new,y1_new,n1.ax,n1.ay)
    n0=n1.prev
    n2=n1.next
@@ -1117,7 +1085,6 @@ function rope:relax()
    n1.next=nil
    n1.prev=nil
   else n0=n0.next end
-  else n0=n0.next end
  end
 end
 
@@ -1130,7 +1097,7 @@ function rope:_check_sane()
  local qxs,qys={},{}
  while true do 
   local n1=n0.next
-  if (n1==nil) break 
+  if (not n1) break 
 
   _rast(qxs,qys,flr(n0.ax*2),flr(n0.ay*2),flr(n1.ax*2),flr(n1.ay*2)) 
   n0=n1
@@ -1152,21 +1119,21 @@ function rope:_check_sane()
  end
  local function _blocked(qx,qy)
   for i in all(_possible_tiles(qx,qy)) do
-   if (not level:mcoll(i.mx,i.my)) return false
+   if (not level:mcoll(i.mx,i.my)) return 
   end
   return true
  end
 
  -- find cases where i move through an impassable zone
  for i=1,#qxs do
-  if (_blocked(qxs[i],qys[i])) return false
+  if (_blocked(qxs[i],qys[i])) return 
  end
 
  -- find cases where i am cut off diagonally
  for i=3,#qxs do
   local qx1,qy1=qxs[i-1],qys[i-1]
   if qx1%2==0 and qy1%2==0 then
-   local ok=false
+   local ok
    for m0 in all(_possible_tiles(qxs[i-2],qys[i-2])) do
     for m2 in all(_possible_tiles(qxs[i],qys[i])) do
      local mx0,my0=m0.mx,m0.my
@@ -1183,49 +1150,75 @@ function rope:_check_sane()
     end
    end
 
-   if (not ok) return false
+   if (not ok) return 
   end
  end
  return true
 end
 
-function would_stick(x0,y0,anchor,x2,y2)
- local x1,y1=anchor.ax,anchor.ay
+function would_stick(anchor,x0,y0,x1,y1,x2,y2)
+ x1,y1=x1 or anchor.ax,y1 or anchor.ay
 
- local dx=x2-x0
- local dy=y2-y0
+ local dx,dy=x2-x0,y2-y0
+ if (x1==x0 and y1==y0) return 
+ if (x1==x2 and y1==y2) return 
 
- if (x1==x0 and y1==y0) return false
- if (x1==x2 and y1==y2) return false
+ local function switch_ends() 
+  dx,dy,x0,y0,x2,y2=-dx,-dy,x2,y2,x0,y0
+ end
 
- local adx,ady
- local x1_new,y1_new
+ local function signs(douter,dinner)
+  local adb=sgn0(dinner)
+  return -sgn0(douter)*adb,adb
+ end
+
+ local adx,ady,x1_new,y1_new
  if abs(dx)>abs(dy) then
-  if (x0>x2) dx,x0,y0,x2,y2=-dx,x2,y2,x0,y0
-  local dprop=(x1-x0)/dx
-  x1_new,y1_new=x1,y0+dprop*(y2-y0)
-  ady=sgn0(y1_new-y1)
-  adx=0
-  if (y0>y2) adx=ady
-  if (y0<y2) adx=-ady
+  if (x0>x2) switch_ends()
+  x1_new,y1_new=x1,y0+(x1-x0)/dx*dy
+  adx,ady=signs(dy,y1_new-y1)
  else
-  if (y0>y2) dy,x0,y0,x2,y2=-dy,x2,y2,x0,y0
-  local dprop=(y1-y0)/dy
-  x1_new,y1_new=x0+dprop*(x2-x0),y1
-  adx=sgn0(x1_new-x1)
-  ady=0
-  if (x0>x2) ady=adx
-  if (x0<x2) ady=-adx
+  if (y0>y2) switch_ends()
+  x1_new,y1_new=x0+(y1-y0)/dy*dx,y1
+  ady,adx=signs(dx,x1_new-x1)
  end
 
- local wouldnt=anchor.dropped or (anchor.adx!=adx or anchor.ady!=ady)
-
- return not wouldnt,x1_new,y1_new,adx,ady
+ return 
+  anchor and anchor.adx==adx and anchor.ady==ady,
+  x1_new,y1_new
 end
 
-function rope:be_pushed_by(anchor,ax_old,ay_old)
+function rope:experience_anchor_moves(moves)
+ self:_be_dragged_by(moves)
+ self:_be_pushed_by(moves)
+ self:relax()
+end
+
+function rope:_be_dragged_by(moves)
+ local n=self.src
+ while n do
+  for t in all(moves) do
+   local ax_old,ay_old,ax_new,ay_new=unpack(t)
+   if (ax_old==n.ax and ay_old==n.ay) n.dest={ax_new,ay_new} break
+  end
+  n=n.next
+ end
+
+ n=self.src
+ while n do
+  if (n.dest) self:_drag(n,unpack(n.dest)) n.dest=nil
+  n=n.next
+ end
+end
+
+function rope:_be_pushed_by(moves)
+ for i in all(moves) do
+  self:_be_pushed_by1(unpack(i))
+ end
+end
+
+function rope:_be_pushed_by1(ax_old,ay_old,ax_new,ay_new,anch)
  local n0=self.src
- local ax_new,ay_new=anchor.ax,anchor.ay
  while true do
   n1=n0.next
   if (not n1) return
@@ -1235,37 +1228,30 @@ function rope:be_pushed_by(anchor,ax_old,ay_old)
 
   local nxmn,nxmx = _mnmx(nx0,nx1)
   local nymn,nymx = _mnmx(ny0,ny1)
-  -- printh(tostring({anchor,nxmn,nxmx,nymn,nymx}))
 
   if
-   (ax_new!=ax_old or (nxmn<=anchor.ax and anchor.ax<=nxmx)) and 
-   (ay_new!=ay_old or (nymn<=anchor.ay and anchor.ay<=nymx)) and 
+   (ax_new!=ax_old or (nxmn<ax_new and ax_new<nxmx)) and 
+   (ay_new!=ay_old or (nymn<ay_new and ay_new<nymx)) and 
 
    (_which_side(ax_old,ay_old,nx0,ny0,nx1,ny1)!= 
     _which_side(ax_new,ay_new,nx0,ny0,nx1,ny1) 
-   ) and would_stick(nx0,ny0,anchor,nx1,ny1)
+   ) and would_stick(anch,nx0,ny0,nil,nil,nx1,ny1)
   then
-   -- printh("found (in): "..tostring({{nx0,ny0},{nx1,ny1}, anchor}))
    local nx05,ny05
    if ax_new==ax_old then
-    nx05=anchor.ax
+    nx05=ax_new
     ny05=ny0+(nx05-nx0)/(nx1-nx0) * (ny1-ny0)
-    -- printh("found (x): "..tostring({nx05,ny05}))
    elseif ay_new==ay_old then
-    ny05=anchor.ay
+    ny05=ay_new
     nx05=nx0+(ny05-ny0)/(ny1-ny0) * (nx1-nx0)
-    -- printh("found (y): "..tostring({nx05,ny05}))
-   else
-    assert(false,"wtf?")
    end
 
-   local n05={ax=nx05,ay=ny05,associated_with=anchor,prev=n0,next=n1}
-   --printh("adding: "..tostring({nx05,ny05,anchor}))
+   local n05={ax=nx05,ay=ny05,prev=n0,next=n1}
    n0.next=n05
    n1.prev=n05
-   self:_drag(n05,anchor.ax,anchor.ay)
-   -- printh("dragged: "..tostring({n05.ax,n05.ay,anchor}))
-   -- printh("local: "..tostring(n0.associated_with).."->"..tostring(n05.associated_with).."->"..tostring(n1.associated_with))
+   -- printh("creating: "..tostring{anch,{n0.ax,n0.ay},{n05.ax,n05.ay},{n1.ax,n1.ay}})
+   -- printh("dragging: "..tostring{anch,{n05.ax,n05.ay},{ax_new,ay_new}})
+   self:_drag(n05,ax_new,ay_new)
   else
    n0=n0.next
   end
@@ -1280,7 +1266,7 @@ function rope:_drag(n1,ax1_new,ay1_new,ax_removing,ay_removing)
     (anchor.ax==ax_removing and anchor.ay==ay_removing)
   end
 
-  if (ax_far0==ax_far1 and ay_far0==ay_far1) return nil
+  if (ax_far0==ax_far1 and ay_far0==ay_far1) return 
 
   if ax_far0==ax_far1 then
    local ax_far=ax_far0
@@ -1292,7 +1278,7 @@ function rope:_drag(n1,ax1_new,ay1_new,ax_removing,ay_removing)
      if 
       not _uncreatable(anchor) and
       (ax0<=anchor.ax and anchor.ax<=ax1) and 
-      would_stick(ax_pivot,ay_pivot,anchor,ax_far,ay_far_new) and
+      would_stick(anchor,ax_pivot,ay_pivot,nil,nil,ax_far,ay_far_new) and
       (
         _which_side(anchor.ax,anchor.ay,ax_pivot,ay_pivot,ax_far,ay_far_old) !=
         _which_side(anchor.ax,anchor.ay,ax_pivot,ay_pivot,ax_far,ay_far_new)
@@ -1313,7 +1299,7 @@ function rope:_drag(n1,ax1_new,ay1_new,ax_removing,ay_removing)
      if 
       not _uncreatable(anchor) and
       (ay0<=anchor.ay and anchor.ay<=ay1) and 
-      would_stick(ax_pivot,ay_pivot,anchor,ax_far_new,ay_far) and
+      would_stick(anchor,ax_pivot,ay_pivot,nil,nil,ax_far_new,ay_far) and
       (
         _which_side(anchor.ax,anchor.ay,ax_pivot,ay_pivot,ax_far_old,ay_far) !=
         _which_side(anchor.ax,anchor.ay,ax_pivot,ay_pivot,ax_far_new,ay_far)
@@ -1332,30 +1318,26 @@ function rope:_drag(n1,ax1_new,ay1_new,ax_removing,ay_removing)
  n1.ay=ay1_new
 
  local n0=n1.prev
- while true do
-  if (n0==nil) break
+ while n0 do
   local anch=_sweep_radar(
    n0.ax,n0.ay,n1.ax,n1.ay,
    n0.ax,n0.ay,ax1_old,ay1_old,ax1_new,ay1_new
    )
-  if (anch==nil) break
-  local n05={ax=anch.ax,ay=anch.ay,associated_with=anch,prev=n0,next=n1}
-  -- printh("creating pre: "..tostring(n0.associated_with).."->"..tostring(n05.associated_with).."->"..tostring(n1.associated_with))
+  if (not anch) break
+  local n05={ax=anch.ax,ay=anch.ay,prev=n0,next=n1}
   n0.next=n05
   n1.prev=n05
   n0=n05
  end
 
  local n2=n1.next
- while true do
-  if (n2==nil) break
+ while n2 do
   local anch=_sweep_radar(
    n1.ax,n1.ay,n2.ax,n2.ay,
    n2.ax,n2.ay,ax1_old,ay1_old,ax1_new,ay1_new
   )
-  if (anch==nil) break
-  local n15={ax=anch.ax,ay=anch.ay,associated_with=anch,prev=n1,next=n2}
-  -- printh("creating post: "..tostring(n1.associated_with).."->"..tostring(n15.associated_with).."->"..tostring(n2.associated_with))
+  if (not anch) break
+  local n15={ax=anch.ax,ay=anch.ay,prev=n1,next=n2}
   n1.next=n15
   n2.prev=n15
   n2=n15
@@ -1363,7 +1345,7 @@ function rope:_drag(n1,ax1_new,ay1_new,ax_removing,ay_removing)
 end
 
 function _stepfrom(x0,x1)
- local done=false
+ local done
  if x0==x1 then
   return function() 
    if (done) return
@@ -1378,12 +1360,12 @@ function _stepfrom(x0,x1)
  local i=flr(x0)
  local top=flr(x1)
  return function()
-  if (done) return nil
+  if (done) return 
   i+=1
   if i>top then 
    done = true
    if (x1!=flr(x1)) return mul*x1
-   return nil
+   return 
   end
   return mul*i
  end
@@ -1409,25 +1391,25 @@ function rope:collide_mrect(mx0,my0,mw,mh,exclude_src,exclude_dst)
 
  while true do
   local n1=n0.next
-  if (n1==nil) return false
+  if (not n1) return 
 
   local nd=n0
   for i=1,exclude_dst do 
    nd=nd.next
-   if (nd==nil) return false
+   if (not nd) return
   end
 
   local x1,y1,x2,y2=n0.ax,n0.ay,n1.ax,n1.ay
   local function _line_line(x3,y3,x4,y4)
-   local denom=((y4-y3)*(x2-x1)-(x4-x3)*(y2-y1))
+   local denom=(y4-y3)*(x2-x1)-(x4-x3)*(y2-y1)
 
    local ua=
     ((x4-x3)*(y1-y3)-(y4-y3)*(x1-x3))/denom
-   if (ua<0 or ua>1) return false
+   if (ua<0 or ua>1) return 
 
    local ub=
     ((x2-x1)*(y1-y3)-(y2-y1)*(x1-x3))/denom
-   if (ub<0 or ub>1) return false
+   if (ub<0 or ub>1) return
 
    return true
   end
@@ -1448,12 +1430,12 @@ function rope:tug_orientxy()
  local a1=self.dst
  local a0=self.dst.prev
  local dx=a0.ax-a1.ax
- local tdx=nil
+ local tdx
  if (dx>3/8) tdx=1
  if (dx<-3/8) tdx=-1
 
  local dy=a0.ay-a1.ay
- local tdy=nil
+ local tdy
  if abs(dy)>abs(dx)/2 then 
   if (dy>3/8) tdy=1
   if (dy<-3/8) tdy=-1
@@ -1494,11 +1476,11 @@ function rope:_tug(hypothetically)
  end
 
  local latch=self.latch
- if latch!=nil and latch.el=="eyehook" then
+ if latch and latch.el=="eyehook" then
   if (hypothetically) return ancs,0
   player.todo={{
    update=function(s) 
-    if s.rope==nil or s.rope:done() then
+    if not s.rope or s.rope:done() then
      return true
     end
    end
@@ -1506,7 +1488,7 @@ function rope:_tug(hypothetically)
   self:destroy(true)
   return true
  end
- if latch!=nil and latch.el=="crate" then
+ if latch and latch.el=="crate" then
   local dmx,dmy=
    sgn0(latch.dx),
    sgn0(latch.dy)
@@ -1522,7 +1504,7 @@ function rope:_tug(hypothetically)
   local mxa=(pull_anc.x+dmx)\8
   local mya=(pull_anc.y+dmy)\8
   
-  local invalid_move=false
+  local invalid_move
   if 
    (dmx!=0 and sgn0(pull_dx)!=dmx) or
    (dmy!=0 and sgn0(pull_dy)!=dmy) or
@@ -1546,15 +1528,15 @@ function rope:_tug(hypothetically)
   end
  end
 
- if (hypothetically) return ancs,nil
- return false
+ if (hypothetically) return ancs
+ return 
 end
 
 function rope:_calc_push(
  an,a0,a1,af
 )
  local ops={}
- if (an==nil) return ops
+ if (not an) return ops
 
  if a0.x==a1.x then
   -- no far side applying pressure?
@@ -1616,12 +1598,12 @@ function rope:_calc_push(
    -- great!
   else
    local crate=level:get_crate(o.mx,o.my)
-   if crate==nil then
-    break
-   else
+   if crate then
     if not level:can_move(false,o.mx,o.my,o.dmx,o.dmy,0,0) then
      break
     end
+   else
+    break
    end
    add(ops2,o)
   end
@@ -1636,23 +1618,23 @@ function rope:_anchors_simplified()
   return atan2(p1.y-p0.y,p1.x-p0.x)
  end
  a=self.src
- while a!=nil do
+ while a do
   local point={
    x=flr(a.ax*8+0.5),y=flr(a.ay*8+0.5),
    ax=a.ax,ay=a.ay
   }
-  local aw=a.associated_with
+  local aw=level:anchor_at(a.ax,a.ay)
   local l=self.latch
   if aw then
    if (aw.adx==1) point.x-=1
    if (aw.ady==1) point.y-=1
-  elseif a.prev==nil and l then
+  elseif not a.prev and l then
    if (l.ax_offset<0) point.x-=1
    if (l.ay_offset<0) point.y-=1
   end
 
   local p0,p1=points[#points-1],points[#points]
-  if p0==nil then
+  if not p0 then
    add(points,point)
   elseif _slope(p0,p1)==_slope(p1,point) then  -- epsilon?
    points[#points]=point