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Rust Practice Exercises

Temperature Converter in Rust

Convert between Celsius and Fahrenheit with an enum that remembers the unit.

  • Beginner
  • 3 min read
  • 1 runnable example
What you'll learn
  • An enum with data
  • match to convert
  • Formatting with {:.1}
Run code →
convert
100.0°C212.0°F
98.6°F37.0°C
-40.0°C-40.0°F

The unit is part of the value

An enum can record which unit a temperature uses, so the compiler stops you from mixing Celsius and Fahrenheit by accident.

convert matches on the variant and returns the other one. show formats the number with one digit after the decimal point. -40 is the one temperature that is the same on both scales.

Key points

  1. Each variant carries the number.
  2. match returns the other unit.
  3. -40 is the same on both scales.

Runnable Rust example

Rust
Run code →
main.rs
enum Temperature {
    Celsius(f64),
    Fahrenheit(f64),
}

fn convert(temperature: &Temperature) -> Temperature {
    match temperature {
        Temperature::Celsius(c) => Temperature::Fahrenheit(c * 9.0 / 5.0 + 32.0),
        Temperature::Fahrenheit(f) => Temperature::Celsius((f - 32.0) * 5.0 / 9.0),
    }
}

fn show(temperature: &Temperature) -> String {
    match temperature {
        Temperature::Celsius(c) => format!("{c:.1}°C"),
        Temperature::Fahrenheit(f) => format!("{f:.1}°F"),
    }
}

fn main() {
    for input in [Temperature::Celsius(100.0), Temperature::Fahrenheit(98.6), Temperature::Celsius(-40.0)] {
        println!("{} = {}", show(&input), show(&convert(&input)));
    }
}
Get a Run button for this example Result of running the code
100.0°C = 212.0°F
98.6°F = 37.0°C
-40.0°C = -40.0°F

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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Next: Option: Values That May Be Missing →

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