Unset Variable Representations

PML Customisation User Guide

Variables, Objects, Functions and Methods : Unset Variable Representations

Each new data type supports a String() method that returns a string representing the value of the variable. For example:


!X = 2.5	$* defines a variable X of type REAL with 2.5 as its numeric value
!S = !X.String()	$* will be a variable of type STRING, with the value “2.5”

UNSET variables of all built-in data types have an unset representation:


!X = REAL()! S = !X.String()	$* yields the string ’(the empty string)
!X = BOOLEAN() !S = !X.String()	$* yields the string ‘’ (the empty string)
!X = STRING() !S = !X.String()	$* yields the string ‘Unset’
!X = ARRAY() !S = !X.String()	$* yields the string ‘ARRAY’


!X = DIRECTION() !S = !X.String()	$* yields the string ‘Unset’

User-defined data types can also provide a String() method. These also support an UNSET representation, and usually adopt the UNSET representation ‘Unset’.