private Double safeToDouble(final String expression, final VariableList varList) {
        final Formula formula = expression == null ? null : Formula.safeCompile(expression);
        final Value value = formula == null ? null : formula.safeEvaluate(varList::getValue);
        return value == null || !value.isDouble() ? null : value.getAsDouble();
    }
Recalculates all values in this waypoint which are depending on variable list.
Returns whether a recalculation was actually done
main/src/main/java/cgeo/geocaching/models/Waypoint.java