It has come to my attention recently where I would really like to use a constrained vector type. Since C++ is typed language it does not make any sense to often validate the input data into a function for example. An input parameter in a function should be the correct type and shouldn't need validation, in my opinion.

std::vector wrapper with additional template argument declaring the constraining relationship to the vector. Seamless integration to current code, so you shouldn't need to put much effort in refactoring.

All of the below code is from the example.cpp file.

Make a struct with a callable bool operator,

struct constrain_less_than_20 {
    bool operator()(int value) {
        return value < 20;
    }
};
using lessthan20 = nonstd::vector_constrained<int, std::allocator<int>, constrain_less_than_20>;

std::vector<int> normal_vector{10, 11, 12, 13, 14};
lessthan20 third_vector{normal_vector};

lessthan20 second_vector{first_vector};// copy the first_vector
second_vector.assign({10, 11});// overwrite vector values
second_vector.insert(second_vector.end(), {12, 13});
second_vector.push_back(14);

void print(const std::vector<int>& vec) {
    for (const auto& item : vec) {
        printf("Item is %d\n", item);
    }
}
int main() {
    lessthan20 third_vector{normal_vector};
    print(third_vector);
}

• All functions in std::vector where iterator is returned has either been commented or changed to const_iterator.