Function leverage 

pub fn leverage(position_value: f64, effective_margin: f64) -> f64

Calculate the leverage of a position.

leverage = position_value / effective_margin

Returns f64::INFINITY if effective margin is ≤ 0.

Examples

let lev = leverage(1000.0, 100.0);
assert!((lev - 10.0).abs() < 0.001);