Array container

#pragma once

#include <array>
#include <stdexcept>
#include <iterator>
#include <string>

using namespace std;

template <typename T, size_t N>
class StackVector {
public:
    explicit StackVector(size_t a_size = 0) : index_(a_size) {
        if (a_size > arr.size()) {
            throw invalid_argument("Expectations far too large");
        }
    }

    T& operator[](size_t index) {
        if (index >= index_) {
            throw invalid_argument("Out of bounds");
        }
        return arr[index];
    }
    const T& operator[](size_t index) const {
        try {
            return arr[index];
        } catch (invalid_argument& e) {
            throw(e.what());
        }
    }

    typename array<T, N>::iterator begin() {
        return arr.begin();
    }
    typename array<T, N>::iterator end() {
        return arr.begin() + index_;
    }
    typename array<T, N>::iterator begin() const {
        return begin();
    }
    typename array<T, N>::iterator end() const {
        return end();
    }

    size_t Size() const {
        return index_;
    }
    size_t Capacity() const {
        return arr.size();
    }

    void PushBack(const T& value) {
        if(index_ >= arr.size()) {
            throw overflow_error("Container full");
        }
        arr[index_++] = value;
    }
    T PopBack() {
        if(index_ == 0) {
            throw underflow_error("Container empty");
        }
        return arr[--index_];
    }
private:
    size_t index_ = 0;
    array<T, N> arr;
};