Conditionals

This page is still under construction!

Conditionals are a important aspect of a program, allowing it to do specific behaviors with specific inputs.

The language have 4 main kinds of conditional checking: if, elif and else statements and match expressions.

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if, elif and else blocks

if, elif and else are the most basic conditional statement.

These statements allows the formation of conditional cascades, checking one condition after another until one of them is true or the cascade ends.

The condition expression evaluated after the if and elif keywords needs to be or result in a Boolean type.

If false, the code will jump the next declarated statement and continue the process in the seccond statement after the condition.

let sayHello = false

if sayHello
	Std.Console.writeln("Hello, World!")

# This statement is outside the condition!
Std.Console.writeln("Goodbie, World!")

Console Output

Goodbie, World!

When an elif statement is declarated after a if or elif, the condition will be verified only if the conditions above are evaluated as false.

When an else statement is declarated after a if or elif, the statement will be executed only when all the above conditions are evaluated as false.

As the condition chain is evaluated from top to bottom, sometimes is possible to end up with unreachable conditions.

let i32 value = 10

# First condition evaluated.
# as 10 != 0, it will fall to the next elif
if value == 0
	Std.Console.writeln("value is exactly 0!")

# as 10 != 1, it will fall to the next elif
elif value == 1
	Std.Console.writeln("value is exactly 1!")

# as 10 > 5, it will fall to the next elif
elif value < 5
	Std.Console.writeln("Value is lower than 5 but greater than 1!")

# as 10 == 10, the next statement will be processed
elif value >= 10
	Std.Console.writeln("Value is equal or greater than 10!")

# It's impossible to a number to be greater than 11
# and not be greater than 10. This condition is unreachable.
elif value > 11
	Std.Console.writeln("Value is greater than 11!")

# A new if keyword will start a new conditional cascade
if value == 11
	Std.Console.writeln("Value is exactly 11!")

# If all conditions in the cascade evaluate to false,
# the else statement will aways be processed
else
	Std.Console.writeln("Value is not 11")

if more than a statement needs to be executed in case of a condition, it's possible to open a conde block with brackets ({ ... }).

let i32 value = ...

if (value > 30) Std.Console.writeln("Value is greater than 30!")
elif (value < 30) Std.Console.writeln("Value is lesser than 30!")
else {
	# Here, this entire code block will be executed in case of the
	# value be exactly 30.
	Std.Console.writeln("Certainly,")
	Std.Console.writeln("the value is")
	Std.Console.writeln("exactly 30!")
}

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Match

This feature is still not implemented!

Value match expressions are great ways to simplify (and very often, optimize) long if-else blocks. A match expression will test a value against diferent values or conditions and conditionally execute the code of the matched option. If no valid option matches the provided value, it will fall into a default fallback option if provided.

let i32 value = ...

match value {
	case 10     => Std.Console.writeln("value is 10!")
	case 20     => Std.Console.writeln("value is 20!")
	case > 30   => Std.Console.writeln("value is greater than 30!")

	default => Std.Console.writeln("Value is neither 10 or 20, but is less or equal to 30!")
}

# Match blocks can return values too!
let i32 by2 = match value {
	case 10 => 5
	case 20 => 10
	case 30 => 15
	case 40 => 20

	default => value / 2
}

When used as statements and with, match expressions can implement the behavior of directily executing another case block, without testing it's condition. to enable this behavior, use the keyword continue with the block case condition right after it:

typedef Privilege {
	case notAllowed
	case basic
	case moderator
	case admin
}

func ... {
	let Privilege permissionLevel = ...
	let canSee = false
	let canWrite = false
	let canArchive = false

	match permissionLevel {
		default => {
			Std.Console.writeln("Permission denied!")
			Std.Process.exit(1)
		}

		case .admin     => canArchive = true; continue .moderator
		case .moderator => canWrite = true; continue .basic
		case .basic     => csnSee = true
	}
	Std.Console.writeln("User is \{permissionLevel}")
	Std.Console.writeln("Can See:     \{canSee}")
	Std.Console.writeln("Can Write:   \{canWrite}")
	Std.Console.writeln("Can Archive: \{canArchive}")
}