if

if

if

Stack

Stack	Position	Description
Stack(In)	Top	Value
Stack(Out)	Top	-

The value on Stack-Top is converted to { TRUE, FALSE }:

Stack empty	FALSE
numerical value = 0	FALSE
numerical value != 0	TRUE
empty variable(INVALID)	FALSE
Object	TRUE
NULL object	FALSE
other value	TRUE

The following instruction (the following instruction block) is executed when TRUE and is skipped when FALSE. As the table shows, a variable that has not yet been assigned a value returns FALSE.