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6.9 The Constant Definition

A constant definition is of the form

     define @constant := expr;

The constant expression expr will be evalued and the constant @constant will be defined to have this value. The constant must not have been defined previously. The constant is valid from this definition up to the end of the rule file. If you use the keyword default instead of define, you provide a default value for @constant. This means, the value is only preliminary and may be changed by a normal constant definition. After a constant has been used in an expression, its value may not be changed any more.