ILOG OPL Development Studio Language Reference Manual

The null valueThe null value is a special value used in some places to specify an absence of information.For example, an array element which has not yet been set has a default value of null. The nullvalue is not to be confused with the undefined value, which also specifies an absence ofinformation in some contexts. See section The undefined value below.The null value can be referenced in programs with the keyword null :null -> the null valueWhen converted to a number, null yields zero (0).Methods of nullThere is only one method of null.Methods of nullSyntax Effectnull.toString() Returns the string "null".I L O G O P L D E V E L O P M E N T S T U D I O L A N G U A G ER E F E R E N C E M A N U A L259