// general
println!("{variable}: {var:width$.precision$}");

// {} as placeholder
// Positional arguments {0}, {1}
println!("{0}, this is {1}. {1}, this is {0}", "Alice", "Bob");

// can have named arguments
// {key}
    println!("{subject} {verb} {object}",
             object="the lazy dog",
             subject="the quick brown fox",
             verb="jumps over");

// special foamtting using `:`
// {:b} for binary: output 10
println!("{} of {:b} people know binary, the other half doesn't", 1, 2); 

// width
// All of these print "Hello x    !"
println!("Hello {:5}!", "x");
println!("Hello {:1$}!", "x", 5);
println!("Hello {1:0$}!", 5, "x");
println!("Hello {:width$}!", "x", width = 5);


// alignment using <, ^, or >
println!("{number:>width$}", number=1, width=6);

// padding
println!("{number:0>width$}", number=1, width=6);

// fill and alignment
assert_eq!(format!("Hello {:<5}!", "x"),  "Hello x    !");
assert_eq!(format!("Hello {:-<5}!", "x"), "Hello x----!");
assert_eq!(format!("Hello {:^5}!", "x"),  "Hello   x  !");
assert_eq!(format!("Hello {:>5}!", "x"),  "Hello     x!");

// alignment might not work for some types, particularly `Debug` trait
// `format` first
println!("Hello {:^15}!", format!("{:?}", Some("hi"))); // => "Hello   Some("hi")   !"

// Hello {arg 0 ("x")} is {arg 1 (0.01) with precision specified inline (5)}
println!("Hello {0} is {1:.5}", "x", 0.01);

// Hello {arg 1 ("x")} is {arg 2 (0.01) with precision specified in arg 0 (5)}
println!("Hello {1} is {2:.0$}", 5, "x", 0.01);

// Hello {arg 0 ("x")} is {arg 2 (0.01) with precision specified in arg 1 (5)}
println!("Hello {0} is {2:.1$}", "x", 5, 0.01);

// Hello {next arg ("x")} is {second of next two args (0.01) with precision
//                          specified in first of next two args (5)}
println!("Hello {} is {:.*}",    "x", 5, 0.01);

// Hello {next arg ("x")} is {arg 2 (0.01) with precision
//                          specified in its predecessor (5)}
println!("Hello {} is {2:.*}",   "x", 5, 0.01);

// Hello {next arg ("x")} is {arg "number" (0.01) with precision specified
//                          in arg "prec" (5)}
println!("Hello {} is {number:.prec$}", "x", prec = 5, number = 0.01);

println!("{}, `{name:.*}` has 3 fractional digits", "Hello", 3, name=1234.56);
println!("{}, `{name:.*}` has 3 characters", "Hello", 3, name="1234.56");
println!("{}, `{name:>8.*}` has 3 right-aligned characters", "Hello", 3, name="1234.56");

// Hello, `1234.560` has 3 fractional digits
// Hello, `123` has 3 characters
// Hello, `     123` has 3 right-aligned characters

// Derive the `fmt::Debug` implementation for `Structure`. `Structure`
// is a structure which contains a single `i32`.
#[derive(Debug)]
struct Structure(i32);

// Put a `Structure` inside of the structure `Deep`. Make it printable
// also.
#[derive(Debug)]
struct Deep(Structure);

use std::fmt;
impl fmt::Display for Structure {
    // This trait requires `fmt` with this exact signature.
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // Write strictly the first element into the supplied output
        // stream: `f`. Returns `fmt::Result` which indicates whether the
        // operation succeeded or failed. Note that `write!` uses syntax which
        // is very similar to `println!`.
        write!(f, "{}", self.0)
    }
}