Dividing two integers doesn't print as a decimal number in Rust

Question

I'm learning Rust, but when I print a decimal number, only the integer part is printed, not the decimal part:

fn main(){     println!("{:.3}", 22/7); } // This only show 3 

but when I print the decimal number explicitly, it works correctly:

fn main(){     println!("{:.3}", 0.25648); } // this print 0.256 

Answer 1

Just like in C and C++, dividing integers results in another integer. Try this C++ program to see:

#include <iostream>  using namespace std;  int main() {     cout << 22 / 7 << endl;            // 3     cout << 22.0 / 7.0 << endl;        // 3.14286 } 

Similarly in Rust, you need to specify both numbers as floats instead, which is done by putting a decimal anywhere in the number. Try this Rust equivalent of the above program:

fn main() {     println!("{:.3}", 22 / 7);         // 3     println!("{:.3}", 22.0 / 7.0);     // 3.143 } 

If you have variables, you can convert them with as to either f32 or f64, depending on your needs:

fn main() {     let x = 22;     println!("{:.3}", x / 7);          // 3     println!("{:.3}", x as f32 / 7.0); // 3.143 } 

Answer 2

When you are working with integer variables and do not have the option to add decimal points you can convert the integer variables into floats using the as keyword:

fn main() {     let a = 42;     let b = 23;     let c = a / b;  // integer division     let d = a as f64 / b as f64;  // cast both variables to float before division     println!("integer division: {}\nfloat division: {}", c, d); } 

This returns the following values:

integer division: 1 float division: 1.826086956521739