Function double_effect_permissible 

pub fn double_effect_permissible(
    act_permissible: bool,
    bad_intended: bool,
    bad_is_means: bool,
    proportionate: bool,
) -> bool

Doctrine of Double Effect: an act with a foreseen-but-unintended bad side effect is permissible iff ALL four conditions hold:

1. the act itself is not wrong (act_permissible);
2. the bad effect is NOT intended, only foreseen (!bad_intended);
3. the bad effect is NOT the means to the good (!bad_is_means);
4. proportionality — the good is not outweighed by the bad (proportionate).