Error when creating a class Object

Question

I'm trying to create an object but apparently it gives some sort of error with the constructor... what? My code that looks like this:

#include <iostream>
#include "Pila.h"
#include "Functions.cpp"
#include <cstring>
using namespace std;
int error = 0;
class Hyogen{
private:
    char *kozui;
    int p_close;
    int p_open;
    int err_par, err_op, err_end, err_start;
public:
    Hyogen(char *a);
    bool Verify();
    char *Elaborate();
    void Errors();
};

Hyogen::Hyogen(char *a){
    kozui = a;
    err_par = 0;
    err_op = 0;
    err_end = 0;
    err_start = 0;
    p_close = 0;
    p_open = 0;
}

bool Hyogen::Verify(){
    for(int i=0;i<strlen(kozui);i++){
        if(i == strlen(kozui)){
            if(error != 0){
                cout<<"uwu";
                return false;
                break;}
            else{
                cout<<"owo";
                return true;}
            }

        check_parentesis(kozui, p_close, p_open);

        if(p_close > p_open || p_open > p_close){
            error++;
            err_par++;
        }

        if(i == 0)
            if(check_start_various(kozui)){
                error++;
                err_start++;
            }

        if(check_operator(kozui)){

            if(check_mul_div(kozui))
                break;

            if(check_doubleop(kozui)){
                error++;
                err_op++;
            }
        }

        if(i == strlen(kozui))
            if(check_end_various(kozui)){
                err_end++;
                error++;
            }
    }
}

int main()
{
    Hyogen koz;
    char *espressione;
    espressione = new char[50];
    cout<<"Inserisci l'espressione: ";
    cin>>espressione;
    return 0;
}

The error I'm getting is the following:

main.cpp: In function ‘int main()’:
main.cpp:76:12: error: no matching function for call to ‘Hyogen::Hyogen()’
     Hyogen koz;
            ^~~
main.cpp:20:1: note: candidate: Hyogen::Hyogen(char*)
 Hyogen::Hyogen(char *a){
 ^~~~~~
main.cpp:20:1: note:   candidate expects 1 argument, 0 provided
main.cpp:7:7: note: candidate: constexpr Hyogen::Hyogen(const Hyogen&)
 class Hyogen{
       ^~~~~~
main.cpp:7:7: note:   candidate expects 1 argument, 0 provided
main.cpp:7:7: note: candidate: constexpr Hyogen::Hyogen(Hyogen&&)
main.cpp:7:7: note:   candidate expects 1 argument, 0 provided

What's happening? What do I have to do? It seems like I have to provide an argument when I create the object, but how? (I need to pass "espressione")

Answer 1

In the line:

Hyogen koz;

you create object of class with default constructor, which you do not have in the class definition. You have to define default constructor:

Hyogen() { };

Or using in C++11:

Hyogen() = default; 

Answer 2

int main()
{
    //Hyogen koz;        Move this
    char *espressione;
    espressione = new char[50];
    cout<<"Inserisci l'espressione: ";
    cin>>espressione;
    Hyogen koz(espressione);    // To here and add parameter
    return 0;
}

DEMO (with some extraneous code removed).

Answer 3

#include <iostream>
#include "Pila.h"
#include "Functions.cpp"
#include <cstring>
using namespace std;
int error = 0; 
class Hyogen{
private:
    char *kozui;
    int p_close;
    int p_open;
    int err_par, err_op, err_end, err_start; public:
    Hyogen(char *a);
    bool Verify();
    char *Elaborate();
    void Errors(); };
public:
    Hyogen() {}
//  ^^^^^^^^^^^   
    Hyogen(char *a);
    bool Verify();
    char *Elaborate();

    void Errors();
};

as already answered in the comments, you need a default constructor

ClassName ( ) ;
ClassName() = default ;

are other options how to do it