4.1 KiB
4.1 KiB
Formatting
Positional arguments
1.ππ
/* Fill in the blanks */
fn main() {
println!("{0}, this is {1}. {1}, this is {0}", "Alice", "Bob"); // => Alice, this is Bob. Bob, this is Alice
assert_eq!(format!("{1}{0}", 1, 2), __);
assert_eq!(format!(__, 1, 2), "2112");
println!("Success!");
}
Named arguments
2.ππ
fn main() {
println!("{argument}", argument = "test"); // => "test"
/* Fill in the blanks */
assert_eq!(format!("{name}{}", 1, __), "21");
assert_eq!(format!(__,a = "a", b = 'b', c = 3 ), "a 3 b");
/* Fix the error */
// Named argument must be placed after other arguments
println!("{abc} {1}", abc = "def", 2);
println!("Success!");
}
Padding with string
3.ππ By default, you can pad string with spaces
fn main() {
// The following two are padding with 5 spaces
println!("Hello {:5}!", "x"); // => "Hello x !"
println!("Hello {:1$}!", "x", 5); // => "Hello x !"
/* Fill in the blanks */
assert_eq!(format!("Hello __!", 5, "x"), "Hello x !");
assert_eq!(format!("Hello __!", "x", width = 5), "Hello x !");
println!("Success!");
}
4.πππ Left align, right align, pad with specified characters.
fn main() {
// Left align
println!("Hello {:<5}!", "x"); // => Hello x !
// Right align
assert_eq!(format!("Hello __!", "x"), "Hello x!");
// Center align
assert_eq!(format!("Hello __!", "x"), "Hello x !");
// Left align, pad with '&'
assert_eq!(format!("Hello {:&<5}!", "x"), __);
println!("Success!");
}
5.ππ You can pad numbers with extra zeros.
fn main() {
println!("Hello {:5}!", 5); // => Hello 5!
println!("Hello {:+}!", 5); // => Hello +5!
println!("Hello {:05}!", 5); // => Hello 00005!
println!("Hello {:05}!", -5); // => Hello -0005!
/* Fill in the blank */
assert!(format!("{number:0>width$}", number=1, width=6) == __);
println!("Success!")
;}
Precision
6.ππ Floating point precision
/* Fill in the blanks */
fn main() {
let v = 3.1415926;
println!("{:.1$}", v, 4); // same as {:.4} => 3.1416
assert_eq!(format!("__", v), "3.14");
assert_eq!(format!("__", v), "+3.14");
assert_eq!(format!("__", v), "3");
println!("Success!");
}
7.πππ String length
fn main() {
let s = "Hello, world!";
println!("{0:.5}", s); // => Hello
assert_eq!(format!("Hello __!", 3, "abcdefg"), "Hello abc!");
println!("Success!");
}
Binary, octal, hex
- format!("{}", foo) -> "3735928559"
- format!("0x{:X}", foo) -> "0xDEADBEEF"
- format!("0o{:o}", foo) -> "0o33653337357"
8.ππ
fn main() {
assert_eq!(format!("__", 27), "0b11011");
assert_eq!(format!("__", 27), "0o33");
assert_eq!(format!("__", 27), "0x1b");
assert_eq!(format!("__", 27), "0x1B");
println!("{:x}!", 27); // Hex with no prefix => 1b
println!("{:#010b}", 27); // Pad binary with 0, width = 10, => 0b00011011
println!("Success!");
}
Capture the environment
9.πππ
fn get_person() -> String {
String::from("sunface")
}
fn get_format() -> (usize, usize) {
(4, 1)
}
fn main() {
let person = get_person();
println!("Hello, {person}!");
let (width, precision) = get_format();
let scores = [("sunface", 99.12), ("jack", 60.34)];
/* Make it print:
sunface: 99.1
jack: 60.3
*/
for (name, score) in scores {
println!("{name}: __");
}
}
Others
Example
fn main() {
// Exponent
println!("{:2e}", 1000000000); // => 1e9
println!("{:2E}", 1000000000); // => 1E9
// Pointer address
let v= vec![1, 2, 3];
println!("{:p}", v.as_ptr()); // => 0x600002324050
// Escape
println!("Hello {{}}"); // => Hello {}
}
You can find the solutions here(under the solutions path), but only use it when you need it :)