How to print any float number with point?

help
1

If i write this:

let x: f32 = 10.0;
println!("let x: f32 = {}", x);

I get a string
let x: f32 = 10

But i want to output 10.0 (with point!!!)
I need it for rust codegen. But this is not a valid rust code.

2 
println!("let x: f32 = {:.1}", x};

For details, check out std::fmt

1 Like
3

This cut precision to 1.
I need a more general method because i need to generate rs file with array of floats
for example:

static A: [f32; 5] = [1.0, 2.01, 3.57656, 4.0, 5.55435];

4

I don't know an answer to your exact question. But perhaps your requirement is satisfied by the following statement:
println!("let x = {}f32", x);

3 Likes
5

Thanks!

6

Does this statement really work ?
I cannot find a better way to deal with your requirement, here are two alternative ways:

7

Yes - this is exactly what i need.
Thanks!

8

Relative question:
How i can print float in this form 1.0e-40 ?

9

Check out dtoa which serde_json uses for printing floating point numbers in e-notation.

extern crate dtoa;

use std::io;

fn main() {
    print!("let x = ");
    dtoa::write(io::stdout(), 1e-40).unwrap();
}
10

I found that format!("{:e}", 0.111) do the job

11

https://stackoverflow.com/a/53640992/11639569
Using the precision format specifier is the correct answer, but to print all available precision , simply refrain from specifying the number of digits to display:

// prints 1
println!("{:.}", 1_f64);

// prints 0.000000000000000000000000123
println!("{:.}", 0.000000000000000000000000123_f64);
12

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