Conditional expressionsΒΆ

Conditional expressions evaluate and return boolean (TRUE and FALSE) expressions for conditional and looping expressions. They can contain conditional operators, and and or.

Examples of conditional expressions:

; The branch is taken if SomeVar is TRUE, *or* both the following things are true:
; SomeOtherVar is TRUE and AnotherVar is FALSE.
(if (or SomeVar (and SomeOtherVar (not AnotherVar)))
        (= x 10)
        (= x 20)

; The or and and operators can take multiple arguments. In this case, if either SomeVar,
; AnotherVar or AThirdVar are TRUE, the branch will be taken.
(if (or SomeVar AnotherVar AThirdVar)
        (= x 10)

; Sometimes it can be useful to place the condition terms on more than one line
; Here the branch is taken if the ego is on green, its x coordinate is less than 100,
; and it has the radio transmitter in its inventory.
(if (and
                (& ctlGREEN (gEgo onControl:))
                (< 100 (gEgo x?))
                (gEgo has: INV_TRANSMITTER)
        (Print "The transmitter begins to beep")