Variables

Definition

All programming languages must have a way for the user to store and retrieve values. The objects that do this are called variables.

These are not the same as variables in mathematics, however. Consider the statement \(x = y^2 + 5\). In mathematics, this is an equality: it states a relationship between \(x\) and \(y\). In programming, however, this is an assignment statement: assuming that the value of \(y\) had been previously been defined, it sets the value of (refered to by) \(x\) to the value of the expression \(y^2 + 5\). For example, if \(y = 5\), then \(x = 30\).

Using Variables in ZHP

In ZHP, variables are created when they are assigned (and initialized). Assignment statements are of the form [identifier] = [value] (identifier is a string of alphabets, digits and underscores which does not start with a digit). Examples are below:

Dynamically vs Statically Typed Languages

ZHP is a dynamically typed language. This means that the type of object refered by variables is not set until the script is running. In contrast, in statically typed languages like Java, C, C++, etc., variables must adhere to a specific type.

As a mathematical analogy, think of the type of a variable to be the mathematical set to which it belongs. For example, when we write x = 5, we expect that the type of x is that of an integer: x belongs to the set of integers. Hence, with statically typed languages, the domain of a variable is static, whereas in dynamically typed languages, the domain of a variable is dynamic.