Is there anything in Rust to convert a binary string to an integer?

Question

My binary resides as a string right now, I was hoping to format! it as an integer the same way I formatted my integer to binary: format!("{:b}", number).

I have a larger string of binary that I'm taking slices out of in a loop, so let's assume one of my slices is:

let bin_idx: &str = "01110011001";

I want to format that binary into an integer:

format!("{:i}", bin_idx);

This gives a compiler error:

error: unknown format trait `i`
 --> src/main.rs:3:21
  |
3 |     format!("{:i}", bin_idx);
  |                     ^^^^^^^

I also tried d and u and got the same error.

Shepmaster · Accepted Answer · 2020-10-20 14:18:25Z

69

First of all, you should be using the official docs; those you pointed to are way outdated.

You have a string and you can't format a string as an integer. I think what you want is a parser. Here's a version using from_str_radix:

fn main() {
    let bin_idx = "01110011001";
    let intval = isize::from_str_radix(bin_idx, 2).unwrap();
    println!("{}", intval);
}

(playground)

edited Oct 20, 2020 at 14:18

Shepmaster

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answered Dec 22, 2014 at 16:53

oli_obk

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Comments

grmmgrmm · Accepted Answer · 2022-05-01 07:26:52Z

2

As an alternative you can use:

let bstr = "11010101";
let i = i32::from_str_radix(bstr, 2).expect("Not a binary number!");
println!("{i}");

Which should print 213.

EDIT: Posted that answer as I thought isize for some reason was not available in my embedded rust project. Was just a typo though...

answered May 1, 2022 at 7:26

grmmgrmm

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Comments

Edmunds Beks · Accepted Answer · 2020-10-20 14:10:50Z

0

I made a function up by myself, and it works!

fn binary_to_u32(s: String) -> u32 {
let mut binary_digit =  s.chars().count();
let mut real_num: u32 = 0;
for c in s.chars() { 
    let mut temp_var = 2u32.pow(binary_digit.try_into().unwrap());
    temp_var /= 2;
    if c == '1'{
        real_num += temp_var;
    }
    binary_digit -= 1;
}
return real_num; }

Also, if you have need for any other integer size, just change u32 to anything you like with some replace shortcut in your text editor.

answered Oct 20, 2020 at 14:10

Edmunds Beks

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5 Comments

Shepmaster Over a year ago

Why would you use this instead of the one in the standard library that is thoroughly tested?

Edmunds Beks Over a year ago

1. It suits all integer type in rust 2. I thought it is easier to write this simple function myself than look for thing that could be non-existing.

Shepmaster Over a year ago

It suits all integer type — as does the existing answer.

Edmunds Beks Over a year ago

I did not knew that. Thank you! Maybe I am bad at Google-ing because I did not find it.

Dmitry Kochkin Over a year ago

also this version has suboptimal performance with pow and division in a loop. Instead multiplication and addition would be much better.

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