test player-relative paths

segment/path update logic was somewhat backwards.

the result is definitely good enough for the kind of movements I want!

arrays_profiling.p8

@@ -0,0 +1,504 @@
+pico-8 cartridge // http://www.pico-8.com
+version 42
+__lua__
+-- prof: cpu cycle counter v1.4
+--  BY PANCELOR
+--[[------------------------
+
+
+use this cart to precisely
+measure code execution time
+
+--------------------------------
+         ★ overview ★
+--------------------------------
+| tab 0 | usage guide          |
+| tab 1 | (internals)          |
+| tab 2 | your code here       |
+--------------------------------
+
+
+-----------------------
+-- ★ usage guide ★ --
+-----------------------
+
+
+웃: i have two code snippets;
+    which one is faster?
+
+🐱: edit the last tab with your
+    snippets, then run the cart.
+    it will tell you precisely
+    how much cpu it takes to
+    run each snippet.
+
+    the results are also copied
+    to your clipboard.
+
+
+
+웃: what do the numbers mean?
+
+🐱: the cpu cost is reported
+    as lua and system cycle
+    counts. look up stat(1)
+    and stat(2) for more info.
+
+    if you're not sure, just
+    look at the first number.
+    lower is faster (better)
+
+
+
+웃: why "{locals={9}}"
+    in the example?
+
+🐱: accessing local variables
+    is faster than global vars.
+
+    so if your test involves
+    local variables, simulate
+    this by passing them in:
+
+      prof(function(a)
+        sqrt(a)
+      end,{ locals={9} })
+
+    /!\     /!\     /!\     /!\
+    local values from outside
+    the current scope are also
+    slower to access! example:
+
+      global = 4
+      local outer = 4
+      prof(function(x)
+        local _ = x --fast
+      end,function(x)
+        local _ = outer --slow
+      end,function(x)
+        local _ = global --slow
+      end,{ locals={4} })
+    /!\     /!\     /!\     /!\
+
+
+
+웃: can i do "prof(myfunc)"?
+
+🐱: no, this sometimes gives
+    wrong results! always use
+    inline functions:
+
+      prof(function()
+        --code for myfunc here
+      end)
+
+    as an example, "prof(sin)"
+    reports "-2" -- wrong! but
+    "prof(function()sin()end)"
+    correctly reports "4"
+
+    (see the technical notes at
+    the start of the next tab
+    for a brief explanation.
+    technically, "prof(myfunc)"
+    will work if myfunc was made
+    by the user, but you will
+    risk confusing yourself)
+
+
+
+---------------
+ ★ method 2 ★
+---------------
+
+
+
+this cart is based on
+code by samhocevar:
+https://www.lexaloffle.com/bbs/?pid=60198#p
+
+if you do this method, be very
+careful with local/global vars.
+it's very easy to accidentally
+measure the wrong thing.
+
+here's an example of how to
+measure cycles (ignoring this
+cart and using the old method)
+
+  function _init()
+    local a=11.2 -- locals
+
+    local n=1024
+    flip()
+    local tot1,sys1=stat(1),stat(2)
+    for i=1,n do   end --calibrate
+    local tot2,sys2=stat(1),stat(2)
+    for i=1,n do local _=sqrt(a) end --measure
+    local tot3,sys3=stat(1),stat(2)
+
+    function cyc(t0,t1,t2) return ((t2-t1)-(t1-t0))*128/n*256/stat(8)*256 end
+    local lua = cyc(tot1-sys1,tot2-sys2,tot3-sys3)
+    local sys = cyc(sys1,sys2,sys3)
+    print(lua.."+"..sys.."="..(lua+sys).." (lua+sys)")
+  end
+
+run this once, see the results,
+then change the "measure" line
+to some other code you want
+to measure.
+
+note: wrapping the code inside
+"_init()" is required, otherwise
+builtin functions like "sin"
+will be measured wrong.
+(the reason is explained at
+the start of the next tab)
+
+
+
+---------------
+ ★ method 3 ★
+---------------
+
+
+
+another way to measure cpu cost
+is to run something like this:
+
+  function _draw()
+    cls(1)
+    local x=9
+    for i=1,1000 do
+      local a=sqrt(x) --snippet1
+  --    local b=x^0.5 --snippet2
+    end
+  end
+
+while running, press ctrl-p to
+see the performance monitor.
+the middle number shows how much
+of cpu is being used, as a
+fraction. (0.60 = 60% used)
+
+now, change the comments on the
+two code snippets inside _draw()
+and re-run. compare the new
+result with the old to determine
+which snippet is faster.
+
+note: every loop iteration costs
+an additional 2 cycles, so the
+ratio of the two fractions will
+not match the ratio of the 
+execution time of the snippets.
+but this method can quickly tell
+you which snippet is faster.
+
+
+
+]]
+
+-->8
+--[[ profiler.lua
+more info: https://www.lexaloffle.com/bbs/?tid=46117
+
+usage:
+  prof(function()
+    memcpy(0,0x200,64)
+  end,function()
+    poke4(0,peek4(0x200,16))
+  end)
+
+passing locals:
+  prof(
+    function(a,b)
+      local c=(a+1)*(b+1)-1
+    end,
+    function(a,b)
+      local c=a*b+a+b
+    end,
+    {locals={3,5}}
+  )
+
+getting global/local variables exactly right
+is very tricky; you should always use inline
+functions like above; if you try e.g. prof(sin)
+the results will be wrong.
+
+
+# minutiae / notes to self:
+---------------------------
+doing this at top-level is awkward:
+  for _=1,n do       end -- calibrate
+  for _=1,n do sin() end -- measure
+b/c sin is secretly local at top-level,
+so it gives a misleading result (3 cycles).
+do it inside _init instead for a
+more representative result (4 cycles).
+
+## separate issue:
+------------------
+if you call prof(sin), it gives the wrong result (-2 cycles) because
+it's comparing sin() against noop() (not truly nothing).
+but we want the noop() there for normal inline prof() calls,
+to avoid measuring the cost of the indirection
+(calling func() from inside prof() is irrelevant to
+how cpu-expensive func()'s body is)
+]]
+
+-- prof(fn1,fn2,...,fnN,[opts])
+--
+-- opts.locals: values to pass
+-- opts.name: text label
+-- opts.n: number of iterations
+function prof(...)
+  local funcs={...}
+  local opts=type(funcs[#funcs])=="table" and deli(funcs) or {}
+
+  -- build output string
+  local msg=""
+  local function log(s)
+    msg..=s.."\n"
+  end
+
+  if opts.name then
+    log("prof: "..opts.name)
+  end
+  for fn in all(funcs) do
+    local dat=prof_one(fn,opts)
+    log(sub("  "..dat.total,-3)
+      .." ("
+      ..dat.lua
+      .." lua, "
+      ..dat.sys
+      .." sys)")
+  end
+
+  -- copy to clipboard
+  printh(msg,"@clip")
+  -- print + pause
+  cls()
+  stop(msg)
+end
+
+function prof_one(func, opts)
+  opts = opts or {}
+  local n = opts.n or 0x200 --how many times to call func
+  local locals = opts.locals or {} --locals to pass func
+
+  -- we want to type
+  --   local m = 0x80_0000/n
+  -- but 8MHz is too large to fit in a pico-8 number,
+  -- so we do (0x80_0000>>16)/(n>>16) instead
+  -- (n is always an integer, so n>>16 won't lose any bits)
+  local m = 0x80/(n>>16)
+  assert(0x80/m << 16 == n, "n is too small") -- make sure m didn't overflow
+  local fps = stat(8)
+
+  -- given three timestamps (pre-calibration, middle, post-measurement),
+  --   calculate how many more CPU cycles func() took compared to noop()
+  -- derivation:
+  --   T := ((t2-t1)-(t1-t0))/n (frames)
+  --     this is the extra time for each func call, compared to noop
+  --     this is measured in #-of-frames -- it will be a small fraction for most ops
+  --   F := 1/30 (seconds/frame) (or 1/60 if this test is running at 60fps)
+  --     this is just the framerate that the tests run at, not the framerate of your game
+  --   M := 256*256*128 = 0x80_0000 = 8MHz (cycles/second)
+  --     (PICO-8 runs at 8MHz; see https://www.lexaloffle.com/dl/docs/pico-8_manual.html#CPU)
+  --   cycles := T frames * F seconds/frame * M cycles/second
+  -- optimization / working around pico-8's fixed point numbers:
+  --   T2 := T*n = (t2-t1)-(t1-t0)
+  --   M2 := M/n = (M>>16)/(n>>16) := m (e.g. when n is 0x1000, m is 0x800)
+  --   cycles := T2*M2*F
+  local function cycles(t0,t1,t2)
+    local diff = (t2-t1)-(t1-t0)
+    local e1 = "must use inline functions -- see usage guide"
+    assert(0<=diff,e1)
+    local thresh = 0x7fff.ffff/(m/fps)
+    local e2 = "code is too large or slow -- try profiling manually with stat(1)"
+    assert(diff<=thresh,e2)
+    return diff*(m/fps)
+  end
+
+  local noop = function() end -- this must be local, because func is local
+  flip() --avoid flipping mid-measurement
+  local atot,asys=stat(1),stat(2)
+  for _=1,n do noop(unpack(locals)) end -- calibrate
+  local btot,bsys=stat(1),stat(2)
+  for _=1,n do func(unpack(locals)) end -- measure
+  local ctot,csys=stat(1),stat(2)
+
+  -- gather results
+  local tot=cycles(atot,btot,ctot)
+  local sys=cycles(asys,bsys,csys)
+  return {
+    lua=tot-sys,
+    sys=sys,
+    total=tot,
+  }
+end
+
+-->8
+-- your code here
+
+bigarr = (function()
+  local ret = {}
+  for i=1,100 do
+   ret[i]=i
+  end
+  return ret
+ end)()
+
+--edit me:
+prof(function()
+ local a, sum = bigarr, 0
+ for x=1,#a do
+  sum += a[x]
+ end
+end,function()
+ local a, sum = bigarr, 0
+ for v in all(a) do
+  sum += v
+ end
+end,function()
+ local a, sum = bigarr, 0
+ foreach(a, function(v) sum+= v end)
+end,{ locals={} })
+
+-- "locals" (optional) are
+-- passed in as args. see the
+-- usage guide for details.
+
+__label__
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collision_profiling.p8

@@ -0,0 +1,495 @@
+pico-8 cartridge // http://www.pico-8.com
+version 42
+__lua__
+-- prof: cpu cycle counter v1.4
+--  BY PANCELOR
+--[[------------------------
+
+
+use this cart to precisely
+measure code execution time
+
+--------------------------------
+         ★ overview ★
+--------------------------------
+| tab 0 | usage guide          |
+| tab 1 | (internals)          |
+| tab 2 | your code here       |
+--------------------------------
+
+
+-----------------------
+-- ★ usage guide ★ --
+-----------------------
+
+
+웃: i have two code snippets;
+    which one is faster?
+
+🐱: edit the last tab with your
+    snippets, then run the cart.
+    it will tell you precisely
+    how much cpu it takes to
+    run each snippet.
+
+    the results are also copied
+    to your clipboard.
+
+
+
+웃: what do the numbers mean?
+
+🐱: the cpu cost is reported
+    as lua and system cycle
+    counts. look up stat(1)
+    and stat(2) for more info.
+
+    if you're not sure, just
+    look at the first number.
+    lower is faster (better)
+
+
+
+웃: why "{locals={9}}"
+    in the example?
+
+🐱: accessing local variables
+    is faster than global vars.
+
+    so if your test involves
+    local variables, simulate
+    this by passing them in:
+
+      prof(function(a)
+        sqrt(a)
+      end,{ locals={9} })
+
+    /!\     /!\     /!\     /!\
+    local values from outside
+    the current scope are also
+    slower to access! example:
+
+      global = 4
+      local outer = 4
+      prof(function(x)
+        local _ = x --fast
+      end,function(x)
+        local _ = outer --slow
+      end,function(x)
+        local _ = global --slow
+      end,{ locals={4} })
+    /!\     /!\     /!\     /!\
+
+
+
+웃: can i do "prof(myfunc)"?
+
+🐱: no, this sometimes gives
+    wrong results! always use
+    inline functions:
+
+      prof(function()
+        --code for myfunc here
+      end)
+
+    as an example, "prof(sin)"
+    reports "-2" -- wrong! but
+    "prof(function()sin()end)"
+    correctly reports "4"
+
+    (see the technical notes at
+    the start of the next tab
+    for a brief explanation.
+    technically, "prof(myfunc)"
+    will work if myfunc was made
+    by the user, but you will
+    risk confusing yourself)
+
+
+
+---------------
+ ★ method 2 ★
+---------------
+
+
+
+this cart is based on
+code by samhocevar:
+https://www.lexaloffle.com/bbs/?pid=60198#p
+
+if you do this method, be very
+careful with local/global vars.
+it's very easy to accidentally
+measure the wrong thing.
+
+here's an example of how to
+measure cycles (ignoring this
+cart and using the old method)
+
+  function _init()
+    local a=11.2 -- locals
+
+    local n=1024
+    flip()
+    local tot1,sys1=stat(1),stat(2)
+    for i=1,n do   end --calibrate
+    local tot2,sys2=stat(1),stat(2)
+    for i=1,n do local _=sqrt(a) end --measure
+    local tot3,sys3=stat(1),stat(2)
+
+    function cyc(t0,t1,t2) return ((t2-t1)-(t1-t0))*128/n*256/stat(8)*256 end
+    local lua = cyc(tot1-sys1,tot2-sys2,tot3-sys3)
+    local sys = cyc(sys1,sys2,sys3)
+    print(lua.."+"..sys.."="..(lua+sys).." (lua+sys)")
+  end
+
+run this once, see the results,
+then change the "measure" line
+to some other code you want
+to measure.
+
+note: wrapping the code inside
+"_init()" is required, otherwise
+builtin functions like "sin"
+will be measured wrong.
+(the reason is explained at
+the start of the next tab)
+
+
+
+---------------
+ ★ method 3 ★
+---------------
+
+
+
+another way to measure cpu cost
+is to run something like this:
+
+  function _draw()
+    cls(1)
+    local x=9
+    for i=1,1000 do
+      local a=sqrt(x) --snippet1
+  --    local b=x^0.5 --snippet2
+    end
+  end
+
+while running, press ctrl-p to
+see the performance monitor.
+the middle number shows how much
+of cpu is being used, as a
+fraction. (0.60 = 60% used)
+
+now, change the comments on the
+two code snippets inside _draw()
+and re-run. compare the new
+result with the old to determine
+which snippet is faster.
+
+note: every loop iteration costs
+an additional 2 cycles, so the
+ratio of the two fractions will
+not match the ratio of the 
+execution time of the snippets.
+but this method can quickly tell
+you which snippet is faster.
+
+
+
+]]
+
+-->8
+--[[ profiler.lua
+more info: https://www.lexaloffle.com/bbs/?tid=46117
+
+usage:
+  prof(function()
+    memcpy(0,0x200,64)
+  end,function()
+    poke4(0,peek4(0x200,16))
+  end)
+
+passing locals:
+  prof(
+    function(a,b)
+      local c=(a+1)*(b+1)-1
+    end,
+    function(a,b)
+      local c=a*b+a+b
+    end,
+    {locals={3,5}}
+  )
+
+getting global/local variables exactly right
+is very tricky; you should always use inline
+functions like above; if you try e.g. prof(sin)
+the results will be wrong.
+
+
+# minutiae / notes to self:
+---------------------------
+doing this at top-level is awkward:
+  for _=1,n do       end -- calibrate
+  for _=1,n do sin() end -- measure
+b/c sin is secretly local at top-level,
+so it gives a misleading result (3 cycles).
+do it inside _init instead for a
+more representative result (4 cycles).
+
+## separate issue:
+------------------
+if you call prof(sin), it gives the wrong result (-2 cycles) because
+it's comparing sin() against noop() (not truly nothing).
+but we want the noop() there for normal inline prof() calls,
+to avoid measuring the cost of the indirection
+(calling func() from inside prof() is irrelevant to
+how cpu-expensive func()'s body is)
+]]
+
+-- prof(fn1,fn2,...,fnN,[opts])
+--
+-- opts.locals: values to pass
+-- opts.name: text label
+-- opts.n: number of iterations
+function prof(...)
+  local funcs={...}
+  local opts=type(funcs[#funcs])=="table" and deli(funcs) or {}
+
+  -- build output string
+  local msg=""
+  local function log(s)
+    msg..=s.."\n"
+  end
+
+  if opts.name then
+    log("prof: "..opts.name)
+  end
+  for fn in all(funcs) do
+    local dat=prof_one(fn,opts)
+    log(sub("  "..dat.total,-3)
+      .." ("
+      ..dat.lua
+      .." lua, "
+      ..dat.sys
+      .." sys)")
+  end
+
+  -- copy to clipboard
+  printh(msg,"@clip")
+  -- print + pause
+  cls()
+  stop(msg)
+end
+
+function prof_one(func, opts)
+  opts = opts or {}
+  local n = opts.n or 0x200 --how many times to call func
+  local locals = opts.locals or {} --locals to pass func
+
+  -- we want to type
+  --   local m = 0x80_0000/n
+  -- but 8MHz is too large to fit in a pico-8 number,
+  -- so we do (0x80_0000>>16)/(n>>16) instead
+  -- (n is always an integer, so n>>16 won't lose any bits)
+  local m = 0x80/(n>>16)
+  assert(0x80/m << 16 == n, "n is too small") -- make sure m didn't overflow
+  local fps = stat(8)
+
+  -- given three timestamps (pre-calibration, middle, post-measurement),
+  --   calculate how many more CPU cycles func() took compared to noop()
+  -- derivation:
+  --   T := ((t2-t1)-(t1-t0))/n (frames)
+  --     this is the extra time for each func call, compared to noop
+  --     this is measured in #-of-frames -- it will be a small fraction for most ops
+  --   F := 1/30 (seconds/frame) (or 1/60 if this test is running at 60fps)
+  --     this is just the framerate that the tests run at, not the framerate of your game
+  --   M := 256*256*128 = 0x80_0000 = 8MHz (cycles/second)
+  --     (PICO-8 runs at 8MHz; see https://www.lexaloffle.com/dl/docs/pico-8_manual.html#CPU)
+  --   cycles := T frames * F seconds/frame * M cycles/second
+  -- optimization / working around pico-8's fixed point numbers:
+  --   T2 := T*n = (t2-t1)-(t1-t0)
+  --   M2 := M/n = (M>>16)/(n>>16) := m (e.g. when n is 0x1000, m is 0x800)
+  --   cycles := T2*M2*F
+  local function cycles(t0,t1,t2)
+    local diff = (t2-t1)-(t1-t0)
+    local e1 = "must use inline functions -- see usage guide"
+    assert(0<=diff,e1)
+    local thresh = 0x7fff.ffff/(m/fps)
+    local e2 = "code is too large or slow -- try profiling manually with stat(1)"
+    assert(diff<=thresh,e2)
+    return diff*(m/fps)
+  end
+
+  local noop = function() end -- this must be local, because func is local
+  flip() --avoid flipping mid-measurement
+  local atot,asys=stat(1),stat(2)
+  for _=1,n do noop(unpack(locals)) end -- calibrate
+  local btot,bsys=stat(1),stat(2)
+  for _=1,n do func(unpack(locals)) end -- measure
+  local ctot,csys=stat(1),stat(2)
+
+  -- gather results
+  local tot=cycles(atot,btot,ctot)
+  local sys=cycles(asys,bsys,csys)
+  return {
+    lua=tot-sys,
+    sys=sys,
+    total=tot,
+  }
+end
+
+-->8
+-- your code here
+
+--edit me:
+prof(function(b1,b2)
+	return 
+	  b1[1]<=b2[3]
+	  and b1[2]<=b2[4]
+	  and b1[3]>=b2[1]
+	  and b1[4]>=b2[2]
+end,function(b1, b2)
+	return 
+	  b1.x1<=b2.x2
+	  and b1.y1<=b2.y2
+	  and b1.x2>=b2.x1
+	  and b1.y2>=b2.y1
+end,{ locals={{1,1,1,1,x1=1,x2=1,y1=1,y2=1},{1,1,1,1,x1=1,x2=1,y1=1,y2=1}} })
+
+-- "locals" (optional) are
+-- passed in as args. see the
+-- usage guide for details.
+
+__label__
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