Using math.ceil

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#1

Hi there, I wanted to try using math.ceil for a game, but I have never used it before. The api info says that it returns the smallest number greater than or equal to X. Is there a way I can make it always be greater than? Because I can’t think of an instance where I would need to use it for equal to?

#2

Not understanding what you’re asking for.

You want a function such that ceil(5) == 6 and ceil(5.1) == 6 instead of ceil(5) == 5?

Default behavior of math.ceil is that math.ceil(x) will be x if x is an integer, and will be x - x % 1 + 1 if x`` has a fractional component. So: ceil(5) == 5 and ceil(5.1) == 6

#3

Yes, because I had a value for a table, and it was zero, and when I did math.ceil it returned 0, and I don’t want that.

#4

I’m thinking of two scenarios you might be having.

The first is you actually want to do this:

index = math.ceil(x + 1)

and the second is that you want to do this, given what you have said:

index = math.max(math.floor(x + 1), math.ceil(x))

Both are different scenarios.

I think you want the first one because I am assuming that you have an array with indexes being integers 1 to n but n is defined from all numbers between [0, n - 1].

#5

Out of curiosity, why would you not want math.ceil(0) to return 0?

#6

Lua has 1-indexed arrays, which would require incrementing the number by 1. I’m not sure what his issue is though, but I’ve had reasons where I would want behavior as in the first codeblock I described.

#7

I believe that you can index at 0, just that iterators like ipairs and pairs skip over it.

#8

Lua arrays start at 1, not 0. If you define a 0 key it becomes a mixed table because it is now a dictionary.

local a = {}

table.insert(a, "hello")

print(a[0]) -- nil
print(a[1]) -- hello

a[0] = "world"

print(a[0]) -- "world"
print(a[1]) -- hello
#9

What would be the point of the whole function then?

#10

To ceil? math.ceil is equivalent to rounding upwards. If your parameter is already an integer, rounding up is equivalent to rounding to the current value.

2 Likes
#11

Ooooooooooooh I see I thought it would do it even if it was an integer. Thanks

#12

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