LÖVE

Posted: **Thu Aug 11, 2016 2:01 pm**

Error: map.lua:14: attempt to perform arithmetic on global 'mapPosX' (a nil value)

It can not change the global variable is initialized in the same lua file, but only when you start the game

map.lua

Code: Select all

function initMap()
  mapShow = false
  mapPosX = -80;
  mapPosY = -50;
  colorChanged = false;
end

function drawMap()
	lg.draw(gameMap, gameMapQuad, mapPosX, mapPosY);
	lg.draw(gameMapView, gameMapQuad, mapPosX, mapPosY);
end

function moveMap(X,Y)
	nextPosX = mapPosX+X; --Then an error occurs
 	nextPosY = mapPosY+Y; -- Here, too, there is an error
	dx = 0;
	dy = 0;
	r, g, b, a = gameMapData:getPixel(windowWidth/2-nextPosX+dx,windowHeight/2-nextPosY+dy);
	if a >= 50 then
		mapPosX = nexpPosX;
		mapPosY = nextPosY;
	else 
		r, g, b, a = gameMapData:getPixel(windowWidth/2-nextPosX+dx,windowHeight/2-mapPosY+dy)
	   	if a >= 50 then
	    	mapPosX = nextPosX;
	    end
	    r, g, b, a = gameMapData:getPixel(windowWidth/2-mapPosX+dx,windowHeight/2-nextPosY+dy)
	    if a >= 50 then
	    	mapPosY = nextPosY;
	    end
  	end
end

I attach a file to the topic .love Link

Posted: **Thu Aug 11, 2016 4:05 pm**

I'll put the same answer here as well. Just in case. Moderators will do what has to be done anyway

You've got a little tiny typo on line #20 of map.lua.
It's "nextPosX", not "nexpPosX".

Posted: **Thu Aug 11, 2016 5:00 pm**

4aiman wrote:I'll put the same answer here as well. Just in case. Moderators will do what has to be done anyway

You've got a little tiny typo on line #20 of map.lua.
It's "nextPosX", not "nexpPosX".

Thank you for at least one bug fixed

Posted: **Fri Aug 12, 2016 7:41 pm**

You should use luacheck. It's a tool for linting and static analysis of Lua code, and I beleive it could have detected your mistake.

Posted: **Sun Aug 14, 2016 5:58 am**

Rucikir wrote:You should use luacheck. It's a tool for linting and static analysis of Lua code, and I beleive it could have detected your mistake.

Does it work with love2d? I couldn't find any info on that.
Right now it seems to me that this tool will complain about every other love.* function out there.
(Shall we start a separate thread? Anyone?)

Posted: **Tue Aug 16, 2016 6:24 pm**

luacheck detects global variables like 'love'. You can simply add your own global definitions by the command line or with a .luacheckrc file.
As LÖVE uses LuaJIT and exports all its functions in the global table 'love', a good start could be:

Code: Select all

luacheck main.lua --std luajit --globals love

An example on a -very- simple code that looks like OP's problem:

$ luacheck -
local a = b
print(a)
Checking stdin 1 warning

stdin:1:11: accessing undefined variable b

Total: 1 warning / 0 errors in 1 file

The luacheck + LÖVE duo could be difficult to work with, I noticed that a lot of projects make extensive use of globals.

Posted: **Tue Aug 16, 2016 6:55 pm**

Or just use strict.lua, since that's what it's for. Well, almost.

Posted: **Wed Aug 17, 2016 8:33 am**

Ah.... The strict.lua!
The thing which had made my life harsh for a couple of weeks back in early 2015

Anyway, "--globals love" is *not* detection. It's a good thing one can tune up luacheck to accept unknown vars, though.

LÖVE

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Re: erroneous arithmetic operations with a global variable