pub trait UpperExp {
// Required method
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}
Expand description
E
formatting.
The UpperExp
trait should format its output in scientific notation with an upper-case E
.
For more information on formatters, see the module-level documentation.
§Examples
Basic usage with f64
:
Implementing UpperExp
on a type:
use std::fmt;
struct Length(i32);
impl fmt::UpperExp for Length {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let val = f64::from(self.0);
fmt::UpperExp::fmt(&val, f) // delegate to f64's implementation
}
}
let l = Length(100);
assert_eq!(
format!("l in scientific notation is: {l:E}"),
"l in scientific notation is: 1E2"
);
assert_eq!(
format!("l in scientific notation is: {l:05E}"),
"l in scientific notation is: 001E2"
);
Required Methods§
1.36.0 · sourcefn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter.
§Errors
This function should return Err
if, and only if, the provided Formatter
returns Err
.
String formatting is considered an infallible operation; this function only
returns a Result
because writing to the underlying stream might fail and it must
provide a way to propagate the fact that an error has occurred back up the stack.