# Constants

Constants can be provided within a program in two ways. They can either be literal values or named constants.

## Named Constants

The best example of a named constant always seems to be PI. It is a constant value although, because it has a large, possibly infinite number of decimal places, it is usually limited to only a few of those. PI can be variously defined as 3.142, 3.14159265 or to a value with even greater accuracy. It can even be defined as 22/7 for simple calculations. However we define it PI itself is still a constant value.

In the LynPlex interpreter constants are defined as:

`const PI = 3.14159265`

Note: In LynPlexS this would be defined as:

`\$\$pi = 3.14159265`

and in LynPlexC as:

`const PI [as datatype] = 3.14159265`

Assigning a name to a constant value means that you do not have to remember what the actual value is. For example:

`c = 2 * PI * r`

## Constants in Expressions

Constants may be used anywhere in an expression. For example.

`put "The value of PI is" PI`

will show:

`The value of PI is 3.14159265`

## Changing Constants

Although constants are intended to remain the same throughout the program, the primary purpose of defining a value as a constant is to stop it being accidentally modified.

Having defined PI as shown above, the statement:

`PI = 123456`

will be rejected.

If you really want to, you can change any constant value provided that you redefine it as a constant. For example, if you want PI to have a lower precision enter:

`const PI = 3.142`

or

`const PI = 22/7`
 ⇐ Literals LynPlexC Programming Variables ⇒

lynplexc/tutorial/constants.txt · Last modified: 2014/05/25 16:52 (external edit) 