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Version: 6.x

IF ... THEN operator

The IF ... THEN operator creates a property that implements selection with one condition (single form).

Syntax​

IF condition 
    THEN value
    [ELSE alternativeValue]

Description​

The IF ... THEN operator creates an action that implements conditional selection. The condition is defined using a property. If this condition is met, that is, the value of the property does not equal NULL, then the value of the created property will be the value of the property specified in the THEN block; otherwise, the value will be the value of the property in the ELSE block, or NULL if no ELSE block was specified.

Parameters​

  • condition

    Expression defining a condition.

  • value

    An expression whose value will be the value of the created property if the condition is met.

  • alternativeValue

    An expression whose value will be the value of the created property if the condition is not met.

Examples​

price1 = DATA NUMERIC[10,2] (Book);
price2 = DATA NUMERIC[10,2] (Book);
maxPrice (Book b) = IF price1(b) > price2(b) THEN price1(b) ELSE price2(b);

// if h is of another class, it will be NULL
sex (Human h) = IF h IS Male THEN 'Male' ELSE ('Female' IF h IS Female); 

isDifferent(a, b) = IF a != b THEN TRUE;