Eris\Generator\SetGenerator::shrink PHP Method

    public function shrink(GeneratedValue $set)
    {
        // TODO: extract duplication with Generator\SequenceGenerator
        // to do so, implement __toString for every Generator (put it
        // in the interface) and then Extract Class
        // ContainmentCheck::of($this)->on($set);
        // which will use $generator->__toString() in the error message
        if (!$this->contains($set)) {
            throw new DomainException('Cannot shrink {' . var_export($set, true) . '} because ' . 'it does not belong to the domain of this set');
        }
        if (count($set->input()) === 0) {
            return $set;
        }
        $input = $set->input();
        // TODO: make deterministic
        $indexOfElementToRemove = array_rand($input);
        unset($input[$indexOfElementToRemove]);
        $input = array_values($input);
        return GeneratedValue::fromValueAndInput(array_map(function ($element) {
            return $element->unbox();
        }, $input), array_values($input), 'set');
    }