Constant

The constant operator is used to create properties without parameters which always return the same value. This value can be static objects of custom and built-in classes as well as the special NULL value. The value class is fixed by the value itself:

Constant value	Value class
Static object of a custom class	the class in whose declaration the object is listed
Built-in value	that value's built-in class
NULL	none — the surrounding context supplies a class where one is required

There is no FALSE constant — the false value is represented by NULL.

Language

Constants are written as references to static objects for custom-class values, and as literals for built-in-class values and NULL.

Examples

CLASS Direction {
    north, east, south, west // declaring static objects
}

// A constant property is created from a Direction.north object which is then used 
// by the comparison operator to construct the isNorth property
isNorth (Direction d) = d == Direction.north;  

// A constant property is created from a literal describing the date
defaultDate() = 1982_07_13;                         

CLASS Man;
age 'Age' = DATA INTEGER (Man);
// A constant property is created from an integer (integer literal)
isChild (Man m) = age(m) < 17;