Asercje c++

#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <string>
#include <cstdlib>
#include <fstream>
#include <cassert>

using namespace std;

struct el {
    int v;
    el* next = NULL;
    el* prev = NULL;
    el(int v);
    virtual ~el();
};

el::el(int _v) {
    this->v = _v;
    //cout << "el(" << _v << ")" << endl;
}

el::~el() {
    el* a = this->prev;
    el* b = this->next;
    if (a != NULL)
        a->next = b;
    if (b != NULL)
        b->prev = a;
}

class List {
    el* head = NULL;
    el* tail = NULL;

public:
    virtual ~List();
    el* add(int a);
    void showRightToLeft();
    void showLeftToRight();
};



List::~List() {
    el* e = this->head;
    while (e != NULL) {
        el* temp = e;
        e = e->next;
        delete temp;
    }
}

el* List::add(int _a) {
    el* current = new el(_a);
    assert(current != NULL);

    if (this->head == NULL) {
        //dodanie pierwszego elementu
        this->head = current;
        this->tail = current;
        return current;
    }

    if (current->v < (this->head)->v) {
        //dodanie z przodu
        el* e = this->head;
        current->next = e;
        e->prev = current;
        this->head = current;
        return current;
    }

    el* next = this->head->next;
    while (next != NULL && current->v > next->v) {
        next = next->next;
    }
    if (next == NULL) {
        //dodanie na końcu
        el* e = this->tail;
        e->next = current;
        current->prev = e;
        this->tail = current;
        return current;
    }

    //dodanie w środku
    el* a = next->prev;
    el* b = next;
    a->next = current;
    b->prev = current;
    current->prev = a;
    current->next = b;
    return current;
}

void List::showLeftToRight() {
    el* e = this->head;
    while (e != NULL) {
        cout << e->v << " ";
        e = e->next;
    }
    cout << endl;
}

void List::showRightToLeft() {
    el* e = this->tail;
    while (e != NULL) {
        cout << e->v << " ";
        e = e->prev;
    }
    cout << endl;
}

void checkRange(int var, int min, int max) {
    assert(var>=min && var<=max);
    cout << var << " znajduje sie w ustalonym zakresie " << min << ":" << max << "." << endl;
}

bool try_stoi(int & i, const string & s) {
    try {
        size_t pos;
        i = stoi(s, &pos);
        return pos == s.size();
    }
    catch (const std::invalid_argument&) {
        return false;
    }
}

int main(int argc, char* argv[])
{
    assert(argc==4);
    string fileName = argv[1];
    int min = atoi(argv[2]);
    int max = atoi(argv[3]);
    cout << "Plik: " << fileName << " Zakres: " << min << ":" << max << endl;

    ifstream file;
    file.open(fileName, std::fstream::in);
    assert(file.good());
    cout << "Plik zostal poprawnie otworzony." << endl;

    List* list = new List;
    assert(list != NULL);
    string wiersz;
    while (getline(file, wiersz)) {
        int i;
        bool ok = try_stoi(i, wiersz);
        assert(ok);
        //dodawanie do listy tylko liczb z podanego zakresu
        checkRange(i, min, max);
        list->add(i);
        wiersz.clear();
    }
    file.close();

    cout << "Lista od lewej do prawej: " << endl;
    list->showLeftToRight();
    cout << "Lista od prawej do lewej: " << endl;
    list->showRightToLeft();

    delete list;
    cin >> min;
    return 0;
}