pub trait LowerExp {
// Required method
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}Available on crate feature
std only.Expand description
e formatting.
The LowerExp trait should format its output in scientific notation with a lower-case e.
For more information on formatters, see the module-level documentation.
§Examples
Basic usage with f64:
let x = 42.0; // 42.0 is '4.2e1' in scientific notation
assert_eq!(format!("{x:e}"), "4.2e1");Implementing LowerExp on a type:
use std::fmt;
struct Length(i32);
impl fmt::LowerExp for Length {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let val = f64::from(self.0);
fmt::LowerExp::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§
1.0.0 · 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.