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:
|A single parameter, constant, or non-arithmetic prefix operator|
|A unary arithmetic prefix operator, with the expression passed to it as an operand|
|A unary postfix operator, with the expression passed to it as an operand|
|A binary operator with the expressions passed to it as operands|
|Expression in parentheses|
An expression cannot include context-independent property operators.
wins(team) = DATA INTEGER(Team);
ties(team) = DATA INTEGER(Team);
// The number of points received by the team for the matches played
points(Team team) = wins(team) * 3 + ties(team);
// 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 BonusGame : Game;
// The number of points per game. If the game is bonus, then 3, otherwise 2.
gamePoints(Game game) = 2 (+) (1 IF game IS BonusGame);
// In this example, the order of execution of the operators will be as follows: IS, IF, (+)