Macro std::fmt::format_args

Transforms a format string and arguments into a sequence of chunks.

This macro is implemented in the compiler, and is used as a foundation for other formatting macros, such as format and println. You probably want to use one of those formatting macros instead.

format_args!(receiver, "{} = {}", a, b);  // Expands to: receiver!(a, " = ", b)

Examples

use std::fmt::format_args;
use std::concat;

// This only works where all format arguments are string literals.
let s = format_args!(concat, "{} + {} = {}", "1", "2", "3");

assert_eq!(s, "1 + 2 = 3");
Run this example

use std::fmt::format_args;
use std::typing::type_name;

macro debug($arg...)  {
    {
        let arg = $arg;
        println!("'{}' {}", arg, type_name::<typeof(arg)>());
    }...;
}

// '1' i32
// ' + ' &[u8]
// '2' i32
// ' = ' &[u8]
// '3' i32
format_args!(debug, "{} + {} = {}", 1, 2, 3);
Run this example