Arithmetics with floats and ints

[xela]

Hey there,
I'm relatively new to the rust ecosystem and have a question about arithmetics with floats and ints:
In my scenario i is my iteration value ranging from 1 to 100 (representing the percentage of the lines I want to use). When I want to calculate the amount of lines with the percentage of i, I can do it this way:
let amount_lines = ((i as f32 / 100.0) * lines.len() as f32) as usize;

I was just wondering if there is some kind of easier way to implement this, without using the explicit typecasts all the time. Thanks already.

Greetings
Xela

[tuxmain]

You can multiply before dividing:

i * lines.len() / 100

[xela]

good point, thanks @tuxmain

[tuxmain]

However doing this you have to be sure that i and lines.len() are small enough, or else the multiplication will overflow.

But in this case it means lines.len() is a lot greater than 100, therefore you can do lines.len() / 100 * i without too much loss of precision.