Floor Division in Rust: Integer Division and Remainder

TL ; DR:

• Remember that in Rust, division between integers with / returns only the integral part of the result:

  println!("{}", 10 / 2); // Output: 5
  println!("{}", 15 / 4); // Output: 3
  println!("{}", 20 / 3); // Output: 6
  
  let a = 3;
  let b = 7;
  
  println!("{}", 20 / a); // Output: 6
  println!("{}", b / a); // Output: 2
  

Full lesson:

Remember how we first learn about the division of two integer numbers in primary school?

The quotient is the number of times a division is completed fully, while the remainder is the amount left that doesn't entirely go into the divisor.

Here are some examples:

10 / 2 = quotient 5, remainder 0
15 / 4 = quotient 3, remainder 3
20 / 3 = quotient 6, remainder 2

Integer division

Integer division (/) is a normal division operation except that it returns the integral part of the result (the quotient). In Rust the fractional part is dropped, so the result is rounded toward zero: -7 / 2 is -3, not -4.

println!("{}", 10 / 2); // Output: 5
println!("{}", 15 / 4); // Output: 3
println!("{}", 20 / 3); // Output: 6

It can also be used with variables:

let a = 3;
let b = 7;

println!("{}", 20 / a); // Output: 6
println!("{}", b / a); // Output: 2

Modulo

The modulo operator (%) calculates the remainder of dividing two values:

println!("{}", 10 % 2); // Output: 0
println!("{}", 15 % 4); // Output: 3
println!("{}", 20 % 3); // Output: 2

// Can be used with variables:
let a = 2;
let b = 4;

println!("{}", b % a); // Output: 0
println!("{}", 11 % b); // Output: 3

Quotient and remainder

In programming, we combine both these concepts to get the quotient and remainder of some division:

// Let's divide 26 by 3:
let quotient = 26 / 3;
let remainder = 26 % 3;

println!("{}", quotient); // Output: 8
println!("{}", remainder); // Output: 2

Assignment
Follow the Coding Tutorial and let's practice with quotient and remainder!

Hint
Look at the examples above if you get stuck.