Skip to main content
Version: 7.0

WHILE operator

The WHILE operator creates an action that implements a recursive loop.

Syntax​

WHILE expression [ORDER [DESC] orderExpr1, ..., orderExprN]
[NEW [alias =] className]
DO action

Description​

The WHILE operator creates an action that implements a recursive loop. This operator can add its local parameters while defining a condition. These parameters correspond to the objects being iterated and are not parameters of the created action. You can also use a NEW block to specify the class of the object that will be created for each object collection that meets the condition. The created object is bound to the local parameter named by alias (or added by default), which can be used in the main action.

The object iteration order in the WHILE operator can be specified with the ORDER block. If a new parameter is declared in the expressions that define the order (a parameter not previously encountered in the WHILE clause or in the upper context), the condition that all these expressions are non-NULL is automatically added.

Parameters​

  • expression

    Expression defining a condition. In this expression, you can both access already declared parameters and declare new local parameters.

  • DESC

    Keyword. Specifies a reverse iteration order for object collections.

  • orderExpr1, ..., orderExprN

    A list of expressions that define the order in which object collections will be iterated over. To determine the order, first the value of the first expression is used; then, if equal, the value of the second is used, etc. If the list is undefined, iteration is performed in an arbitrary order.

  • alias

    The name of the local parameter that will correspond to the object being created. Simple ID. If omitted, the parameter is named added.

  • className

    The name of the class of the object to create. Defined by a class ID.

  • action

    Context-dependent action operator describing the action being executed.

Examples​

iterateDates (DATE dateFrom, DATE dateTo)  {
    LOCAL dateCur = DATE();

    dateCur() <- dateFrom;
    WHILE dateCur() <= dateTo DO {
        MESSAGE 'I have a date ' + dateCur();
        dateCur() <- sum(dateCur(), 1);
    }
}