Solution
/// Calculate the magnitude of the given vector. fn magnitude(vector: &[f64; 3]) -> f64 { let mut mag_squared = 0.0; for coord in vector { mag_squared += coord * coord; } mag_squared.sqrt() } /// Change the magnitude of the vector to 1.0 without changing its direction. fn normalize(vector: &mut [f64; 3]) { let mag = magnitude(vector); for item in vector { *item /= mag; } } fn main() { println!("Magnitude of a unit vector: {}", magnitude(&[0.0, 1.0, 0.0])); let mut v = [1.0, 2.0, 9.0]; println!("Magnitude of {v:?}: {}", magnitude(&v)); normalize(&mut v); println!("Magnitude of {v:?} after normalization: {}", magnitude(&v)); }
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Note that in
normalize
we were able to do*item /= mag
to modify each element. This is because we’re iterating using a mutable reference to an array, which causes thefor
loop to give mutable references to each element. -
It is also possible to take slice references here, e.g.,
fn magnitude(vector: &[f64]) -> f64
. This makes the function more general, at the cost of a runtime length check.