Introduction
Printing in Cairo allows you to display messages or debug information during program execution.
Basics
Cairo provides two macros for printing:
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println!: Outputs a message followed by a newline.
-
print!: Outputs a message without a newline.
println!("Hello, Cairo!");
println!("x = {}, y = {}", 10, 20);
Placeholders {} are replaced with provided values.
Use format! to create a ByteArray without immediately printing:
let result = format!("{}-{}-{}", "tic", "tac", "toe");
println!("{}", result); // Output: tic-tac-toe
Custom Data Types
For custom types, implement Display or derive Debug for printing:
#[derive(Debug)]
struct Point { x: u8, y: u8 }
let p = Point { x: 3, y: 4 };
println!("{:?}", p); // Debug output: Point { x: 3, y: 4 }
Hexadecimal Printing
Use {:x} to print integers as hexadecimal:
println!("{:x}", 255); // Output: ff
Instructions
In the magical world of Echoes, there exists a powerful spell called "EchoSpeak".
This spell allows wizards to communicate their thoughts and observations through spoken words, which are written out by magical quills.
To master this spell, wizards must learn how to formulate their words and thoughts clearly and concisely, whether it's about numbers, objects, or complex magical constructs.
Your task as a Wizard's Apprentice is to master the art of EchoSpeak.
This requires you to learn how to print various types of magical data to the enchanted scrolls.
EchoSpeak works by taking a special magical ink, represented by the ByteArray, and inscribing formatted messages to the scroll using spells like println! and print!.
However, when dealing with custom magical constructs like enchanted items or spells, EchoSpeak needs a special incantation to understand how to represent these objects.
That's where your magic comes in - learning to implement special spells known as traits for custom magical items.
Sometimes, wizards need to format their magical words before inscribing them on scrolls.
You'll write a function that formats three magical words into a single message.
Implement a function called format_magical_chant that returns a formatted string in the form of "chant1-chant2-chant3".
Example:
let result = format_magical_chant("Spark", "Shine", "Glow");
assert_eq!(result, "Spark-Shine-Glow");
2. Echoing Custom Enchanted Items
The realm of Echoes is filled with enchanted items.
One such item is the EchoStone, which contains two magical attributes: power and duration.
Your task is to implement the stringify_echo_stone function that converts an EchoStone into a ByteArray in a special format "EchoStone [power: x, duration: y]" by implementing the Display trait.
Example:
let stone = EchoStone { power: 100, duration: 300 };
assert_eq!(stringify(stone), "EchoStone [power: 100, duration: 300]");
3. Debugging the Magic
As a wizard apprentice, debugging is essential for complex magical constructs.
You will create a function that prints an EchoStone for debugging using the Debug trait.
The format should be: "Debugging EchoStone: { power: x, duration: y }".
Example:
let stone = EchoStone { power: 25, duration: 10 };
assert_eq!(format!("{:?}", stone), "Debugging EchoStone: { power: 25, duration: 10 }");
Learning Exercise
