Rust Formatting

In this post, let us explore different ways to format integers, decimal, strings using format specifiers

Formatting Integers

Just to format integers as it-is, we have to pass integers as argument to format macro

    println!("{}", format!("{}", 100));

To zero-pad integers with specific number of digits, in the format macro, specify the length. In this below example, we'll have zero-padded integer with max 10 digits

    println!("{}", format!("{:010}", 5));

Convert number into binary-formatted, just specify #b in format macro as below

    println!("{}", format!("{:#b}", 50));

Convert number into octal-formatted, just specify #o in format macro as below

    println!("{}", format!("{:#o}", 50));

Convert number into hex-formatted, just specify #x or #X in format macro as below

    println!("{}", format!("{:#x}", 50));

If you would like to have 1000 specifier as per locale, it can be achieved using num_format crate. The below example, will format the number 1 billion in US locale

    println!("{}", 1_000_000_000.to_formatted_string(&num_format::Locale::en));

Formatting the number 1 billion in French locale

    println!("{}", 1_000_000_000.to_formatted_string(&num_format::Locale::fr));

Formatting the number 1 billion in Indian locale

    println!("{}", 1_000_000_000.to_formatted_string(&num_format::Locale::en_IN));

Formatting Decimals

To format decimal numbers with specific precision, we can use below specifiers

    println!("{}", format!("{:.5}", 100.02));

In case if the decimal number exceeds the given precision, the number will get rounded-off at nth precision. The below code outputs 100.02782

    println!("{}", format!("{:.5}", 100.02781839));

Formatting String

To format string in left-aligned, we can use below specifier in the macro

    println!("{}", format!("{:<20}", "Rust is awesome"));

To align string in center within given length, we can use below specifier in the macro

    println!("{}", format!("{:^20}", "Rust is awesome"));

To right-align string within given length, we can use below specifier in the macro

    println!("{}", format!("{:>20}", "Rust is awesome"));

In case if you would like to fill the white-space with specific character, we just need to specify the specific character before the respective symbol (^, >, <) in the specifier

    println!("{}", format!("{:*^20}", "Rust is awesome"));

We can use the above specifiers to align integers as well.

All the code examples can be found in this link

Please feel free to share your feedback.

Happy reading!!!