This first edition was written for Lua 5.0. While still largely relevant for later versions, there are some differences.
The third edition targets Lua 5.2 and is available at Amazon and other bookstores.
By buying the book, you also help to support the Lua project.


2.3 – Numbers

The number type represents real (double-precision floating-point) numbers. Lua has no integer type, as it does not need it. There is a widespread misconception about floating-point arithmetic errors and some people fear that even a simple increment can go weird with floating-point numbers. The fact is that, when you use a double to represent an integer, there is no rounding error at all (unless the number is greater than 100,000,000,000,000). Specifically, a Lua number can represent any long integer without rounding problems. Moreover, most modern CPUs do floating-point arithmetic as fast as (or even faster than) integer arithmetic.

It is easy to compile Lua so that it uses another type for numbers, such as longs or single-precision floats. This is particularly useful for platforms without hardware support for floating point. See the distribution for detailed instructions.

We can write numeric constants with an optional decimal part, plus an optional decimal exponent. Examples of valid numeric constants are:

    4     0.4     4.57e-3     0.3e12     5e+20