# Differences

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+ | ====== 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 | ||

+ | |||

+ | ===== Page Links ===== | ||

+ | |||

+ | |< 100% 35% - 28% - 35% >| | ||

+ | | <= [[literals]] ^ | [[start]] ^ | [[variables]] => | | ||