An expression is a combination of property operators and parameters. When an expression is evaluated sequentially in priority order, all the operators are executed.
The result of that execution will be either a property or a parameter (in the case of single-parameter expression). Their value shall be called the value of the expression.
An expression can be described by the following set of recursive rules:
| Rule | Description |
expression := parameter | constant | prefixOperator | A single parameter, constant, or non-arithmetic prefix operator |
expression := prefixArithmOp expression | A unary arithmetic prefix operator, with the expression passed to it as an operand |
expression := expression postfixOp | A unary postfix operator, with the expression passed to it as an operand |
expression := expression binaryOp expression | A binary operator with the expressions passed to it as operands |
expression := ( expression ) | Expression in parentheses |
An expression cannot include context-independent property operators.
Examples
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CLASS Team;
wins(team) = DATA INTEGER(Team);
ties(team) = DATA INTEGER(Team);
points(Team team) = wins(team) * 3 + ties(team); // The number of points received by the team for the matches played
// In this case, the expression is written to the right of the equal sign. It defines a new property called points.
// When calculating the expression, two JOIN operators are first executed: wins(team) and ties(team), substituting the team parameter in the wins and ties properties
// Then the multiplication operator will be executed, which will build a property that returns a number equal to the product of the return value of wins(team) and the number 3
// Then the addition operator will be executed, which will create a property that sums the return values (wins(team) * 3) and ties(team)
// The resulting property will be the result of the expression
CLASS Game;
CLASS BonusGame : Game;
gamePoints(Game game) = 2 (+) (1 IF game IS BonusGame); // The number of points per game. If the game is bonus, then 3, otherwise 2.
// In this example, the order of execution of the operators will be as follows: IS, IF, (+)
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