Basic datatypes

Datatypes are the shapes of data manipulated by an application. Opa uses datatypes to perform sanity and security checks on your application. Opa also uses datatypes to perform a number of optimizations. There are three basic datatypes in Opa: integers, floats, and strings. Also, you can define your type with the keyword type:

type Student = {string name, int age, float score}
Student stu = { name:"li", age:28, score:80.0}

Actually, thanks to a mechanism of type inference, Opa can work in most cases even if you do not provide any type information. For example:

x = 10        // the same as: int x = 10
x = {a:1,b:2} // the type of x is: {a:int, b:int}

So in the rest of this chapter, we will not address type information before variable, but you should know what type it is in your mind. In actual coding, a best practice is to provide the datatypes of our main functions and to let the inference engine pick up the datatypes of all the local variables and minor functions.

Integers

It...