Function proportionality_met 

pub fn proportionality_met(
    harm_expr: &str,
    wrt: &str,
    at: f64,
    advantage: f64,
) -> Option<bool>

Proportionality test: an act is proportionate iff its marginal harm is strictly less than the advantage it secures (∂Harm/∂x < Advantage). None if the harm model is unparseable. The legal proportionality / necessity calculus.