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


const PI = 22/7


programmers_guide/constants.txt · Last modified: 2015/01/06 09:44 by don