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How to Get an Absolute Value in Rust

by | Programming, Rust, Tips

We can calculate the absolute value of a number using the abs() method. We have to specify the numeric type before we call the abs method, for example, if we want a 32-bit signed integer we need to put i32 after the number.

This tutorial will go through how to calculate the absolute value of a numeric value in Rust with code examples.

Example #1: Absolute Value of a Signed Integer

Let’s look at an example where we want to calculate the absolute value of an integer:

fn main() {
    let num = -4
    let abs_num = num.abs();
    println!("{}", abs_num);
}

In the above code, we define the number and then call the abs() method. Let’s run the code to see what happens:

error[E0689]: can't call method `abs` on ambiguous numeric type `{integer}`
 --> src/main.rs:3:23
  |
3 |     let abs_num = num.abs();
  |                       ^^^
  |
help: you must specify a type for this binding, like `i32`
  |
2 |     let num: i32 = -4;
  |         ~~~~~~~~

The error occurs because we did not define the specific numeric type. We need to put an i32 after the number so that Rust knows the number is a 32-bit signed integer. Let’s look at the revised code:

fn main() {
    let num = -4i32
    let abs_num = num.abs();
    println!("{}", abs_num);
}

Let’s run the code to see the result:

4

We successfully calculated the absolute value of -4, which is 4

The absolute method abs() is an available method for most numeric types.

Example #2: Absolute Value of a Signed Float

Let’s look at an example where we want to calculate the absolute value of a floating point. We need to put an f32 after the number so that Rust knows the number is a 32-bit signed float. 

fn main() {

    let num = -3.4f32;

    let abs_num = num.abs();

    println!("{}", abs_num);

}

Let’s run the code to see the result:

3.4

We successfully calculated the absolute value of -3.4, which is 3.4.

Summary

Congratulations on reading to the end of this tutorial! For further reading on Rust, go to the articles:

Have fun and happy researching!