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.
Dyn Compatibility§
This trait is dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety".