Macro std::format_args 1.0.0
[−]
[src]
macro_rules! format_args { ($fmt:expr) => { ... }; ($fmt:expr, $($args:tt)*) => { ... }; }
The core macro for formatted string creation & output.
This macro functions by taking a formatting string literal containing
{}
for each additional argument passed. format_args!
prepares the
additional parameters to ensure the output can be interpreted as a string
and canonicalizes the arguments into a single type. Any value that implements
the Display
trait can be passed to format_args!
, as can any
Debug
implementation be passed to a {:?}
within the formatting string.
This macro produces a value of type fmt::Arguments
. This value can be
passed to the macros within std::fmt
for performing useful redirection.
All other formatting macros (format!
, write!
, println!
, etc) are
proxied through this one. format_args!
, unlike its derived macros, avoids
heap allocations.
For more information, see the documentation in std::fmt
.
Examples
use std::fmt; let s = fmt::format(format_args!("hello {}", "world")); assert_eq!(s, format!("hello {}", "world")); Run