The core macro for formatted string creation & output.

This macro takes as its first argument a callable expression which will receive as its first argument a value of type &fmt::Arguments. This value can be passed to the functions in std::fmt for performing useful functions. All other formatting macros (format!, write!, println!, etc) are proxied through this one.

For more information, see the documentation in std::fmt.

Example

use std::fmt;

let s = format_args!(fmt::format, "hello {}", "world");
assert_eq!(s, format!("hello {}", "world"));

format_args!(|args| {
    // pass `args` to another function, etc.
}, "hello {}", "world");