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I made a mistake in a method and wrapped an entire logical expression in a flr() statement instead of just the number. Instead of an error message the pico-8 would just hang when I tried to run it.

if (flr(self.bottomPaneX == 17)) del(objects,self) spawnWindow()

Above causes pico-8 to hang when you try and run the cart below doesn't

if (flr(self.bottomPaneX) == 17) del(objects,self) spawnWindow()

In a smaller scale test I found that it didn't hang running the following

cls()
test = {}
test.var = 0x42
if(flr(test.var==0x42)) print("reached")

Here is the code which can reproduce the error.

objects = {}
window = {}

function round(fract)
    if fract-flr(fract)>=0.5 then return flr(fract)+1 end
    return flr(fract)
end

function _init( ... )
    spawnWindow()
end

function spawnWindow()
    local obj = {}
    --dimensions for drawing. there are lots so that they can be slightly altered for spooky animations
    obj.topPaneX,obj.topPaneY,obj.topPaneW,obj.topPaneH = 51,27,25,11
    obj.bottomPaneX,obj.bottomPaneY,obj.bottomPaneW,obj.bottomPaneH = 51,30,25,10
    obj.frameX,obj.frameY,obj.frameW,obj.frameH = 51,27,25,21
    obj.colour = 12

    --the object state controls which animation the object is in
    obj.state = 2
    --update method for the object
    obj.update = function(self)
        if(self.state==1) then 
            if(self.bottomPaneY < 37) self.bottomPaneY += 0x0.8
        elseif self.state == 2 then
            self.topPaneX -= 0x1
            self.frameX += 0x1
            self.bottomPaneX -= 0x0.4
            self.bottomPaneW += 0x0.8
            self.bottomPaneY -= 0x0.4
            self.bottomPaneH += 0x0.4
           --This is the fated line top breaks bottom doesn't
            if (flr(self.bottomPaneX == 17)) del(objects,self) spawnWindow()
            if (flr(self.bottomPaneX) == 17) del(objects,self) spawnWindow()
        end
    end

    --draw method for the object
    obj.draw = function(self)
        --remember to save tokens we only need to delcare colour when we are drawing with a different colour to the last thing drawn
        --draw the frame
        rect(self.frameX,self.frameY,self.frameX + self.frameW,self.frameY + self.frameH,self.colour)
        --draw the top pane
        rect(self.topPaneX,self.topPaneY,self.topPaneX + self.topPaneW,self.topPaneY + self.topPaneH)
        line(self.topPaneX + round(self.topPaneW /2),self.topPaneY,self.topPaneX + round(self.topPaneW /2),self.topPaneY + self.topPaneH)
        --draw the bottom pane
        rect(self.bottomPaneX,self.bottomPaneY,self.bottomPaneX + self.bottomPaneW,self.bottomPaneY + self.bottomPaneH)
        line(self.bottomPaneX + round(self.bottomPaneW /2),self.bottomPaneY,self.bottomPaneX + round(self.bottomPaneW /2),self.bottomPaneY + self.bottomPaneH)

    end

    window = obj

    --adds the object to relevant tables
    add(objects,obj)    
end

function _update( ... )
    -- body
    for o in all(objects) do
        o:update()
    end

end

function _draw( ... )
    -- body
    for o in all(objects) do
        o:draw()
    end
end
P#46493 2017-11-19 21:05 ( Edited 2017-11-20 12:37)

::

I think you realized that line doesn't make sense anyway, but what happens is this:

  • self.bottomPaneX==17 => boolean (true/false)
  • flr(boolean) => 0 (I think the argument is ignored when not a number and flr() just returns 0)
  • if (0) ... <=> if (true) ... (anything else than nil and false evaluates to true) => del(objects,self) is ALWAYS executed.

so basically you're deleting everything on your first update, and there's nothing left to draw nor update. since there's not even a cls(), the screen stays as it is and the program loops doing nothing. but Pico-8 doesn't actually hangs.
hope that helps :)

P#46516 2017-11-20 12:37 ( Edited 2017-11-20 12:40)

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