Now its the second week that we are into the internship. today I am starting Lua data types.

Lua is a dynamically typed language. There are no type definitions in the language; each value carries its own type.

There are eight basic types in Lua: nil, boolean, number, string, userdata, function, thread, and table. The type function gives the type name of a given value:

print(type("Hello world")) --> string
print(type(10.4*3)) --> number
print(type(print)) --> function
print(type(type)) --> function
print(type(true)) --> boolean
print(type(nil)) --> nil
print(type(type(X))) --> string
print(type(a)) --> nil (`a' is not initialized)
a = 10
print(type(a)) --> number
a = "a string!!"
print(type(a)) --> string
a = print -- yes, this is valid!
a(type(a)) --> function

The last example will result in "string" no matter the value of X, because the result of type is always a string.

Variables have no predefined types; any variable may contain values of any type:

Notice the last two lines: Functions are first-class values in Lua; so, we can manipulate them like any other value. (More about that in Chapter 6.)

Usually, when you use a single variable for different types, the result is messy code. However, sometimes the judicious use of this facility is helpful, for instance in the use of nil to differentiate a normal return value from an exceptional condition.