What is Nan?

Games
1

What is nan in terms of Lua? Does it equate to nil? If so why doesn’t this code work:
[lua]g.alive = function( event )
print(“Am I Alive”, g.status)
if not g.status then
print(“error”)
g.status = true
end
end
Runtime:addEventListener(“enterFrame”, g.alive)[/lua]

When there is an erroneous call to g.alive in which g.alive is nil it should be set to true, right? But all I get is Am I Alive nan [import]uid: 54716 topic_id: 17034 reply_id: 317034[/import]

2

nan or NaN is usually ‘Not a Number’. You can get these from illegal math operations like dividing by 0. It’s not clear to me how you got nan from the code you pasted. [import]uid: 7563 topic_id: 17034 reply_id: 63910[/import]

3

Oh duh, not a number, epic face palm. It’s not clear to me either lol. Thanks for the response. I know now what to look for. [import]uid: 54716 topic_id: 17034 reply_id: 63913[/import]

4

Is there a way to test for non numbers? I still have no clue where I am passing it in. I should only be having nil or a number. [import]uid: 54716 topic_id: 17034 reply_id: 63931[/import]

5

Not really. Testing for NaN is actually really hard and would require platform/architecture specific tricks if it could be done at all. The best thing is to avoid creating them in the first place. [import]uid: 7563 topic_id: 17034 reply_id: 64044[/import]

6

You could maybe try to use the tonumber() function.
If it can’t convert the parameter to a number it’ll return nil, and if it’s already a number it will just return the number. [import]uid: 70847 topic_id: 17034 reply_id: 64050[/import]

7

Just a guess here, but if g.status is a Boolean type and not a number it could be throwing off the print command where you use a comma to separate the string and g.status. You could try
print(type(g.status))
above line 2 to find out what type g.status is.

Also you could try this for line 2:
print(“Am I Alive” … g.status)
or
(“Am I Alive” … tostring(g.status))

And you could do a check for the correct type (not quite a check for nan but might be just as good). Something like (untested):

If tostring(type(g.status)) ~= “number” then
–do something to handle the wrong type
end
[import]uid: 9422 topic_id: 17034 reply_id: 64055[/import]

8

Thanks ingemar and XenonBl I will try those options. Thing is those variables are only set in two places and are numbers or nil so I am still confused as to what it could be. And what else is in Lua that’s not a table, boolean, numbers, or string??? [import]uid: 54716 topic_id: 17034 reply_id: 64067[/import]

9

From http://www.lua.org/pil/2.html

There are eight basic types in Lua: nil, boolean, number, string, userdata, function, thread, and table. [import]uid: 9422 topic_id: 17034 reply_id: 64072[/import]

10

I know at least half of those would print out something or throw an error for trying use in a string. I will have to look into the rest thanks. [import]uid: 54716 topic_id: 17034 reply_id: 64074[/import]

11

I expect NaN to be a number type in Lua. You won’t be able to distinguish it from any other number.
[import]uid: 7563 topic_id: 17034 reply_id: 64076[/import]

12

Something that’s “Not a Number” (NaN) is a number type??

My head just exploded. [import]uid: 9422 topic_id: 17034 reply_id: 64080[/import]

13

LOL [import]uid: 54716 topic_id: 17034 reply_id: 64146[/import]

14

By definition, Nan should test not equal to itself. So this should work.

print(“Nan Test”)
local myNan = 0/0
local myNanTest = (myNan ~= myNan)
print("myNanTest "…tostring(myNanTest) )

[import]uid: 41667 topic_id: 17034 reply_id: 66100[/import]

15

division by 0 yields inf or -inf, but 0/0 is nan (-nan in Lua demo)

what is nan? it’s of type number but it is not equal to …itself

0/0 is any number, so any number=not a (single) number

but, what is -nan?

[import]uid: 6459 topic_id: 17034 reply_id: 66126[/import]

16

0/0 is indeterminate. And the first rule of indeterminate club, is you don’t talk about indeterminate club.

According to IEEE 754-2008, the sign of a NaN has no meaning. Then again, I have heard that if a particle of NaN meets a particle of -NaN, there is an explosion.

[import]uid: 41667 topic_id: 17034 reply_id: 66533[/import]

17

Thanks all, it was definitely a math problem. [import]uid: 54716 topic_id: 17034 reply_id: 66541[/import]

18

I’ll go back to enjoying garlic naan and try to forget everything I didn’t learn in this thread. [import]uid: 9422 topic_id: 17034 reply_id: 66549[/import]