1.4 Conditionals

if

The master keyword if is used to create a conditional statement.

if password == "1234" then {
    do say ("Access granted")    
} else {
    do say ("Access denied")
}

if is followed by a boolean expression, the then keyword and a block of code and an optional else block.
The boolean expression is evaluated and if it is true, the block of code before is executed.
If the boolean expression is false, the else block is executed.
Example of an if statement with an else extension:

if password == "1234" then {
    do say ("Access granted")
} else if password == "4321" then {
    do say ("Access granted with alternative password")
} else {
    do say ("Access denied")
}

Here password must be equal to "1234" for the first block to be executed.
If password is equal to "4321" the second block is executed.
If password is not equal to "1234" or "4321" the else block is executed.

when

The extension keyword when is also used to create a conditional statement.

do {
    do say ("Access granted")
} when password == "1234"

when is used to create a conditional statement.
when is followed by a boolean expression, a block of code and an optional else block.
The boolean expression is evaluated and if it is true, the block of code before is executed.
If the boolean expression is false, the else block is executed.
Example of a when statement with an else extension:

do {
    do say ("Access granted")
} when password == "1234" else {
    do say ("Access denied")
}

unless

The extension keyword unless is also used to create a conditional statement.
It's the same as when, but the boolean expression is inverted.

do {
    do say ("Access denied")
} unless password == "1234"

Boolean operators

Boolean operators are used to compare values.
Boolean operators return a boolean value. (true or false)

Common boolean operators are:
== equal to
!= not equal to
> greater than
< less than
>= greater than or equal to
<= less than or equal to
&& and
|| or

Example of a boolean expression:

if password == "1234" && username == "Robotnik" then {
    do say ("Access granted")
}

Here password must be equal to "1234" and username must be equal to "Robotnik" for the block to be executed.
here's another example:

if password == "1234" || password == "4321" then {
    do say ("Access granted")
}

Here password must be equal to "1234" or "4321" for the block to be executed.
here's another example:

if age >= 18 then {
    do say ("Access granted")
}

Here age (variable) must be greater or equal to 18 for the block to be executed.
For a full list of operators, go to 2.2 Operators.

extension keywords

On a more advanced note, when and is is actually extension keywords.
extension keywords are functionality that can be added to a master keyword.

set number = 5 when condition
return number unless condition

We'll learn more about do extensions in a later chapter 1.6 Extensions and loops.