Lua: converting from float to int

Question

Even though Lua does not differentiate between floating point numbers and integers, there are some cases when you want to use integers. What is the best way to covert a number to an integer if you cannot do a C-like cast or without something like Python's int?

For example when calculating an index for an array in

idx = position / width

how can you ensure idx is a valid array index? I have come up with a solution that uses string.find, but maybe there is a method that uses arithmetic that would obviously be much faster. My solution:

function toint(n)     local s = tostring(n)     local i, j = s:find('%.')     if i then         return tonumber(s:sub(1, i-1))     else         return n     end end 

Answer 1

You could use math.floor(x)

From the Lua Reference Manual:

Returns the largest integer smaller than or equal to x.

Answer 2

Lua 5.3 introduced a new operator, called floor division and denoted by //

Example below:

Lua 5.3.1 Copyright (C) 1994-2015 Lua.org, PUC-Rio

>12//5

2

More info can be found in the lua manual