From c480295b41621431542628a4f0baea9ca77bda6a Mon Sep 17 00:00:00 2001
From: Kistaro Windrider <kistaro@gmail.com>
Date: Sat, 24 Dec 2022 00:08:10 +0000
Subject: [PATCH] Save some tokens in horrible, horrible ways. (#13)

replace comparisons with bit math bullshit

integers in the range [0, 15] fit entirely in the bit mask 0x000F. integers out of that range will have at least one bit 0x0010 or higher, or will have the sign bit 0x8000 set. so to find out if one of two numbers is out of range [0, 15], we can check the bit mask of their bitwise or.

this saves tokens and cycles. it is also completely illegible. very in the spirit of Pico-8, I love it.

comment the bullshit

it needs it

packed crate representation

don't bother exploding crates into four bools, and then comparing them all individually to a bunch of conditions. absurd bit manipulation bullshit saves cycles and tokens. leaving a crate's movement rule represented as four bits means we can exploit our previous calculation of dx1 and dy1, which must each either be 0x0001 or 0x8FFF, and violently hammer them down to align with this bit-packed representation, giving this glorious little atrocity.

Fix crate math.

I forgot that -1 & 1 = 1 rather than 0 so all the bit math didn't work. But I can fix it with polynomial algebra! this is much better.

Save tokens on movemebnt checks

I promise this is mathematically equivalent-ish to the original. (0.2 and its multiples are nonterminating decimals in base 2, so there's a little jank when the negative shift right is a shift left.)

Trimming

Trim up redundant nil checks, sequential assignments that could be on a shared line, and repeated references to a deeply nested variable.

Reviewed-on: https://git.chromaticdragon.app/pyrex/chameleonic/pulls/13
Co-authored-by: Kistaro Windrider <kistaro@gmail.com>
Co-committed-by: Kistaro Windrider <kistaro@gmail.com>
---
 chameleonic.p8 | 67 +++++++++++++++++++++++---------------------------
 1 file changed, 31 insertions(+), 36 deletions(-)

diff --git a/chameleonic.p8 b/chameleonic.p8
index 8d0c7cd..5af73d7 100644
--- a/chameleonic.p8
+++ b/chameleonic.p8
@@ -438,7 +438,9 @@ function level:spawn_exit()
   if (self:_mget(x,y)!=18) return
   for nx=x-1,x+1 do
    for ny=y-1,y+1 do
-    if nx<0 or ny<0 or nx>15 or ny>15 then
+    -- next check: is at least one of
+    -- nx or ny out of range [0, 15]?
+    if (nx | ny) & 0xFFF0 ~= 0 then
      self._wins[_mix(nx,ny)]=true
     end
    end
@@ -478,16 +480,18 @@ function _mix(mx,my)
   return mx..","..my
 end
 
+-- crate spec:
+-- "up" == 1
+-- "right" == 2
+-- "down" == 4
+-- "left" == 8
+--
+--    +1+
+--    8 2
+--    +4+
 function level:_get_cratedef(s)
- if (s<64 or s>=80) return nil
- 
- local s2=s-64
- return {
-  up=s2&1!=0,
-  right=s2&2!=0,
-  down=s2&4!=0,
-  left=s2&8!=0
- }
+ if (s<64 or s>=80) return
+ return s & 0x000F
 end
 
 function level:get_latch(dx,dy,px,py)
@@ -498,12 +502,7 @@ function level:get_latch(dx,dy,px,py)
  local dx1,dy1=-sgn0(dx),-sgn0(dy)
 
  if crate then
-  if
-   (crate.def.up and dy>0) or
-   (crate.def.down and dy<0) or 
-   (crate.def.left and dx>0) or
-   (crate.def.right and dx<0)
-  then
+  if crate.def & dy1*dy1*(2.5+1.5*dy1)+dx1*dx1*(5-3*dx1) ~= 0 then
    return {
     el="crate",
     dx=dx1,dy=dy1,
@@ -545,12 +544,12 @@ function level:can_move(
  if player.rope then
   local chk=false
   local w,h=1.6,0.2
-  if (dmx==0) w,h=0.2,1.6
-
-  if (dmy==-1) rectx,recty=0.4,-0.8
-  if (dmy==1) rectx,recty=0.4,0.2
-  if (dmx==-1) rectx,recty=-0.8,0.4
-  if (dmx==1) rectx,recty=0.2,0.4
+  if dmx==0 then 
+    w,h=0.2,1.6
+  else
+    dmy = 0
+  end
+  rectx,recty=dmx*(0.4>>>dmx),dmy*(0.4>>>dmy)
 
   if (player.rope:collide_mrect(mx0+rectx,my0+recty,w,h,exclude_src,exclude_dst)) return false
  end
@@ -627,7 +626,7 @@ function player:update()
   end
 
   if kbd:btn(4) then
-   if kbd:btnp(4) and self.rope!=nil then 
+   if kbd:btnp(4) and self.rope then 
     self.rope:destroy()
     kbd:release(4)
    end
@@ -660,7 +659,7 @@ function player:update()
     
     self.todo={{
      update=function()
-      return self.rope==nil or self.rope:latched()
+      return not self.rope or self.rope:latched()
      end
     }}
    elseif kbd:btnp(5) then
@@ -765,7 +764,7 @@ function player:draw()
 
  if self.rope then
   local rx_adj,ry_adj=self.rope:affected_src_xy(rx,ry)
-  if rx_adj!=nil then
+  if rx_adj then
    local drx,dry=rx_adj-rx,ry_adj-ry
    rx,ry=rx+drx,ry+dry
    px,py=px+drx,py+dry
@@ -833,10 +832,7 @@ function rope:update()
  elseif self.state.name=="latched" then
   if (self.latch==nil) wrongbleep:bleep(5) self:destroy() return
 
-  if 
-   self.latch!=nil and
-   self.latch.rec!=nil 
-  then
+  if self.latch and 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
@@ -898,11 +894,10 @@ end
 
 function rope:draw(artificial_px,artificial_py)
  local points,highlight=self:_tug(true)
- if (self.state.name=="done") return
- local perc_to_show=1.0
- local from_end=false
- if (self.state.name=="cast") perc_to_show=self.state.frame/2
- if (self.state.name=="destroy") perc_to_show=(1.0-self.state.frame/8)^2
+ local n,perc_to_show,from_end = self.state.name,1.0,false
+ 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/8)^2
  if (self.state.reelin) from_end=true
 
  points[#points]={x=artificial_px,y=artificial_py}
@@ -1191,7 +1186,7 @@ function rope:be_pushed_by(anchor,ax_old,ay_old)
  local ax_new,ay_new=anchor.ax,anchor.ay
  while true do
   n1=n0.next
-  if (n1==nil) return
+  if (not n1) return
 
   local nx0,ny0=n0.ax,n0.ay
   local nx1,ny1=n1.ax,n1.ay
@@ -1318,7 +1313,7 @@ function _stepfrom(x0,x1)
  local done=false
  if x0==x1 then
   return function() 
-   if (done) return nil
+   if (done) return
    done=true return x0
   end
  end