assert() function throwing an error something wrong with the operator - c++

The error I'm getting is
whole.cpp(384): error C2270: '==' : modifiers not allowed on nonmember functions
whole.cpp(384): error C2805: binary 'operator ==' has too few parameters
whole.cpp(384): error C2274: 'function-style cast' : illegal as right side of '.' operator
I can't seem to pin down the problem though so here is the code
this is the operator implementation in the class
bool operator==(const DateC& p) const{return ( DateC::DateC()== p.DateC() );};
#include <assert.h>
int main(unsigned int argc, char* argv[])
{
DateC f(29,33,11);
DateC::testAdvancesWrap();
};
void DateC::testAdvancesWrap(void)
{
DateC d;
cout << "DateC::testAdvanceWrap()" << endl ;
cout << "*********************" << endl << endl ;
cout << "\tCHECK ADVANCE MULTIPLES:" << endl;
cout << "\t------------------------" << endl;
d.setDay(1);
d.setMonth(12);
d.setYear(1999);
prettyPrint(d);
cout << "ACTION: set date 01-Dec-1999, advance, 31 days, 1 month and 1 year ->" << endl;
d.advance(1,1,31);
assert( d == DateC(1,2,2001) );
cout << "SUCCESS" << endl;
prettyPrint(d);
cout << endl << endl;
}
the rest of the functions working fine it's only the assert()

When you create your own classes, if you want to compare them, you need to create operators for them. Let's say you would like to compare 2 instances of a class Person.
A person consist of a string and an int - lastname and height.
We wish to compare people by their height, so we need to tell the compiler how to do it.
An example:
class Person
{
string lastname;
int height;
bool operator == (const Person& p) const
{
return (this->height == p.height);
}
};
EDIT:
I think you misunderstood my example, you can only compare things that the compiler knows how to compare. Your Date implemantation probably has ints, so if you are checking for equality, you have to check all fields.
Use this-> to have access to the other object's fields in the function.

Related

E0349 no operator ">>" matches these operands

I'm new to C++, so please forgive me if this is extremely simple.
Just trying to make my own independent projects, and then this error happens to me:
E0349 no operator ">>" matches these operands
// usd-to-aud.cpp : This file contains the 'main' function. Program execution begins and ends there.
//
#include <windows.h>
#include <iostream>
// MAIN
int main()
{
std::cout << "Welcome to Currency conversion!\n";
Sleep(1000);
std::cout << "This application is used to convert USD to AUD\n";
Sleep(1000);
int num();
std::cout << "Enter amount in USD: ";
std::cin >> num();
std::cout << num() << " is " << num() * 1.68 << " in AUD.\n";
return 0;
}
Assuming you're not intending to declare a function named num taking no arguments, and calling it repeatedly, simply removing the parentheses at every use of num (declaration included) should fix your problem. If it's not a callable of some sort, you don't want parens here.

how can a void function be called to the main, if there are no returns?

I wanted to create a function that retrieves all the information from previous functions within the same Class, and prints the values that were returned in the format of a bunch of cout statements, there is nothing for me to return in this PrintStatement() function, so I would create a void function, correct? My issue is in the int main(), I cannot cout a void function.
this is my account header file, and the function piece from my account.cpp file.
class Account {
public:
//Object constructor
Account(char firstName[], char lastName[], char sinNumber[], double balance, int accountType, int transactions);
//Object operations
double DepositAmt(double amount);
double WithdrawAmt(double amount);
void PrintStatement();
double getFinalBalance(double fbal);
string getAccountType();
double getTransactions (double Deposit, double Withdraw);
private:
//Object properties
char firstName[255];
char lastName[255];
char sinNumber[255];
double balance;
int accountType;
int transactions;
};
void Account::PrintStatement()
{
cout << "First Name: " << firstName << endl;
cout << "Last Name: " << lastName << endl;
cout << "SIN Number: " << sinNumber << endl;
cout << "Account Type: " << accountType << endl;
cout << "Final Balance: " << balance << endl;
cout << "Transactions: " << transactions << endl;
};
the global variables have already been initialized.
What I've tried:
I originally tried to cout << account.PrintStatement() << endl; however I get an error C2679 (binary '<<' : no operator found which takes a right-hand operand of type 'void' (or there is no acceptable conversion)
I thought maybe changing things to apply to a string function instead would work, but instead I get a bunch of int conversion errors etc.
I'm unsure of what to do.
I am required to put these in a function just to be clear.
I tried using this question https://stackoverflow.com/questions/12766858/how-to-call-void-function-from-main to help me, it made sense that the poster was using a reference, but I do not have that. Is there another way?
I originally tried to cout << account.PrintStatement() << endl;
Well, the expression account.PrintStatement() is abject nothingness because the function has a void return type. As you've indicated, the function returns nothing, so there is nothing to stream to cout.
The function itself has already streamed a bunch of stuff to cout, fulfilling all your couty needs. So, simply invoke it:
account.PrintStatement();
That's it!
Just call the method on your instance of the class. It doesn't need to return anything; it will do the counts you want and then return to main.
When we use cout<<something_here, the compiler will interpret it as "print the value of something_here". Now, something_here can be a lot of things. When it is a function, cout will print the value returned by the function. In your case, the return type is void i.e. nothing. So, there is nothing to print.
To fix your issue, you can directly call account.PrintStatement(); since you have already printed what you wanted to print inside this function.

<insert name of struct> was not declared in this scope

http://pastebin.com/4gvcQm7P
#include <iostream>
using namespace std;
int GenerateID()
{
static int nextID = 0;
return nextID++;
}
void PrintInformation(Employee EmployeeName)
{
cout << EmployeeName << "'s ID is: " << EmployeeName.ID << endl;
cout << EmployeeName << "'s age is: " << EmployeeName.age << endl;
cout << EmployeeName << "'s wage is: " << EmployeeName.wage << endl;
}
int main()
{
struct Employee
{
int ID;
int age;
float wage;
};
Employee Dominic;
Employee Jeffrey;
Dominic.ID = GenerateID();
Dominic.age = 22;
Dominic.wage = 7.10;
Jeffrey.ID = GenerateID();
Jeffrey.age = 28;
Dominic.wage = 7.10;
PrintInformation(Dominic);
PrintInformation(Jeffrey);
return 0;
}
/*
C:\CBProjects\Practise\main.cpp|11|error: variable or field 'PrintInformation' declared void|
C:\CBProjects\Practise\main.cpp|11|error: 'Employee' was not declared in this scope|
C:\CBProjects\Practise\main.cpp||In function 'int main()':|
C:\CBProjects\Practise\main.cpp|39|error: 'PrintInformation' was not declared in this scope|
||=== Build finished: 3 errors, 0 warnings (0 minutes, 0 seconds) ===|
*/
The above pastebin link shows the code I used and the build report. Following this report I attempted to forward declare the struct without including members and then there is an 'incomplete type' error.
What is the solution?
Edit: I'm using c++11
Edit 2: Here is what happens if I try to forward declare the struct, including the members:
http://pastebin.com/rrt4Yjes#
There are two solutions: Make Employee a non-local class/struct or make PrintInformation a template. For the first solution, just move Employee before PrintInformation. The second solution would be:
template< typename Employee >
void PrintInformation(const Employee& EmployeeName)
{
cout << " EmployeeName's ID is: " << EmployeeName.ID << endl;
cout << " EmployeeName's age is: " << EmployeeName.age << endl;
cout << " EmployeeName's wage is: " << EmployeeName.wage << endl;
}
Note that in any case you don't want a copy of Employee just to print some information, hence make the parameter of PrintInformation a constant reference as shown above.
First piece of information in the error is the line number.
C:\CBProjects\Practise\main.cpp|11|error: variable or field 'PrintInformation' declared void|
Line 11. Lets look at line 11.
void PrintInformation(Employee EmployeeName)
This all looks valid, but what's an Employee? We don't find that out until line 21. Your function, PrintInformation wants to make use of the internal plumbing of PrintInformation so the function actually needs to know the full definition of the struct/class.
In addition to all this, you have very explicitly made Employee a private type of main by defining it inside the function. What you are actually declaring is main::Employee.
A few solutions:
Declare "Employee" in the same scope as PrintInformation, i.e. at the global scope at the top of the file after the includes etc.
Or make "PrintInformation" a member function of Employee.
struct Employee
{
void PrintInformation()
{
std::cout << " Employee's ID is: " << ID << '\n';
std::cout << " Employee's age is: " << age << '\n';
std::cout << " Employee's wage is: " << wage << '\n';
}
...
};
...
Dominic.PrintInformation();
Or implement operator<< (probably advanced for where you are right now).
I'd also like to point out an aspect of style that is lining you up for some serious headaches down stream: You're using the same UpperCamelCase for variables and types, but being inconsistent with types. It's going to benefit you if you teach yourself to prefix member variables with something and maintain consistent case early on:
struct Employee // UpperCamel for types.
{
int m_id;
int m_age;
float m_wage;
};
It now becomes very easy to separate local variables and types and member variables. This is going to become especially useful as you start to learn about member functions.
struct Employee // UpperCamel for types.
{
int m_id;
std::string m_name;
int m_age;
float m_wage;
Employee(const std::string& name, int age, float wage)
: m_id(nextID++)
, m_name(name)
, m_age(age)
, m_wage(wage)
{}
...
};
You should declare struct Employee before using it in PrintInformation() or make PrintInformation a template (as #DanielFrey did).
Fix your PrintInformation() to following as you cannot directly print a struct data unless you overloading << for the struct (check out here on how to do this).
void PrintInformation(Employee EmployeeName)
{
cout << " EmployeeName's ID is: " << EmployeeName.ID << endl;
cout << " EmployeeName's age is: " << EmployeeName.age << endl;
cout << " EmployeeName's wage is: " << EmployeeName.wage << endl;
}

operator definition not working right

I am trying to implement a comparison operator but I'm getting the following errors
whole.cpp(384): error C2270: '==' : modifiers not allowed on nonmember functions
whole.cpp(384): error C2805: binary 'operator ==' has too few parameters
whole.cpp(384): error C2274: 'function-style cast' : illegal as right side of '.' operator
I can't seem to pin down the problem though so here is the code
this is the operator implementation in the class
bool operator==(const DateC& p) const
{
return ( DateC::DateC()== p.DateC() );
};
#include <assert.h>
int main(unsigned int argc, char* argv[])
{
DateC f(29,33,11);
DateC::testAdvancesWrap();
};
void DateC::testAdvancesWrap(void)
{
DateC d;
cout << "DateC::testAdvanceWrap()" << endl ;
cout << "*********************" << endl << endl ;
cout << "\tCHECK ADVANCE MULTIPLES:" << endl;
cout << "\t------------------------" << endl;
d.setDay(1);
d.setMonth(12);
d.setYear(1999);
prettyPrint(d);
cout << "ACTION: set date 01-Dec-1999, advance, 31 days, 1 month and 1 year ->" << endl;
d.advance(1,1,31);
assert( d == DateC(1,2,2001) );
cout << "SUCCESS" << endl;
prettyPrint(d);
cout << endl << endl;
}
the rest of the functions working fine it's only the assert()
You can implement comparison operators as member functions or free functions. To implement it as a free function as you are trying to do you need to accept two arguments - the value on the left hand side of = and the value on the right hand side of =. The example below shows how to properly do this.
struct Date
{
int variable_;
};
bool operator==(const Date& lhs, const Date& rhs)
{
return lhs.variable_ == rhs.variable_;
}
To implement the comparison operator as a member function you only need to take one argument which is the value on the right hand size of =. The object owning the comparison operator being executed is the value on the left hand side of =. In this case the operator should be const qualified.
struct Date
{
int variable_;
bool operator==(const Date& rhs) const
{
return variable_ == rhs.variable_;
}
};
In all cases the argument should be taken as a const reference to allow the use of rvalues (temporaries).

C++ STL set of classes - compiler error error C2664

Newbie programmer here trying to work out his homework. I'm trying to use a STL set of classes, but the compiler complains about my code.
car.h
#include <string>
#include <iostream>
#include <time.h>
#include <set>
class Car
{
private:
std::string plateNumber;
std::string description;
std::string dateIn;
std::string timeIn;
public:
Car() {};
~Car() {};
Car(std::string plate, std::string desc)
{
plateNumber = plate;
description = desc;
};
void setPlateNumber(std::string plate) ;
std::string getPlateNumber() const;
void setDesc(std::string desc);
void setTimeDateIn() ;
std::string getTimeIn() const;
std::string getDateIn() const;
std::string getDesc() const;
friend std::ostream & operator<<(std::ostream & os, Car &c);
};
std::ostream & operator<<(std::ostream & os, Car& c)
{
os << "Plate Number: " << c.plateNumber << ", Date In: " << c.dateIn << ", " <<
`"Time in: " << c.timeIn << "Description: " << c.description << std::endl;
return os;
}
bool operator< ( const Car& lhs, const Car& rhs)
{
return ( lhs.getPlateNumber() < rhs.getPlateNumber() );
};
main.cpp
#include "stdafx.h"
#include <iostream>
#include <set>
#include <string>
#include "car.h"
void carEnters(std::set<Car> g);
void carLeaves(std::set<Car> g);
void displayContents(std::set<Car> g);
int main ()
{
char choice [80];
// initialize the sets and iterators
std::set<Car> garage;
do // Loop until user quits
{
std::cout <<
std::endl;
std::cout << "Menu:" << std::endl;
std::cout << "-----" << std::endl;
std::cout << "'1' to enter a new car, or " << std::endl;
std::cout << "'2' to exit the front car, or " << std::endl;
std::cout << "'3' to to list all the cars or." << std::endl;
std::cout << "'0' to close the garage: " << std::endl;
std::cin.getline( choice, 1, '\n');
switch ( choice[0] )
{
case '0' :
std::cout << std::endl << "Thanks for playing...\n";
break;
case '1' :
carEnters(garage);
break;
case '2' :
carLeaves(garage);
case '3' :
displayContents(garage);
break;
default:
std::cout << "I'm sorry, I didn't understand that.\n";
break;
}
} while ( choice[0] != '0' ); // Loop again if the user hasn't quit.
return 0;
}
void carEnters( std::set<Car> g)
{
// Car enters garage
std::cout << "Please enter the plate number:" << std::endl;
std::string plate;
std::cin >> plate;
std::cin.ignore();
std::set<Car>::iterator findPlate;
Car* lookup = new Car;
lookup->setPlateNumber(plate);
findPlate = g.find(*lookup);
if (findPlate != g.end()) // Add car to garage
{
Car *currentCar = new Car ;
// Set car parameters
std::cout << "Please type the entering car's description <Model, Color...
> : " << std::endl;
char desc[80];
std::cin.get(desc, 80 );
std::cin.ignore();
currentCar->setDesc(desc);
currentCar->setTimeDateIn();
currentCar->setPlateNumber(plate);
g.insert(currentCar);
}
else // Plate is already in garage set
{
std::cout << "Sorry, this car is already in the garage!" <<
std::endl;
}
}
void carLeaves( std::set<Car> g)
{
std::string plate;
std::cout << "Which plate is leaving?" << std::endl;
std::cin >> plate;
std::cin.ignore();
// Find car's plate number in the garage set
// for (findPlate=garageSet.begin(); findPlate !=garageSet.end(); findPlate++)
std::set<Car>::iterator findPlate;
Car lookup(plate,"");
findPlate = g.find(lookup);
if (findPlate != g.end())
{
// Display time in and then remove car from set of cars
std::cout << "Car out at " << (*findPlate).getDateIn() << ", " <<
(*findPlate).getTimeIn() << std::endl;
g.erase(findPlate);
}
else
{
std::cout << "Car was not found in set of Cars!" << std::endl;
}
}
// Car class function implementation
void Car::setPlateNumber(std::string p)
{
plateNumber = p;
}
std::string Car::getPlateNumber() const
{
return plateNumber;
}
void Car::setDesc(std::string d)
{
description = d;
}
void Car::setTimeDateIn()
{
char dat[9];
char tim[9];
_strdate_s(dat);
_strtime_s(tim);
dateIn=dat;
timeIn=tim;
}
std::string Car::getTimeIn() const
{
return timeIn;
}
std::string Car::getDateIn() const
{
return dateIn;
}
std::string Car::getDesc() const
{
return description;
}
// Display the car set
void displayContents(std::set <Car> garage)
{
// function displays current contents of the parking garage.
std::set <Car>::iterator carIndex;
std::cout << std::endl << "Here are all the cars parked: " << std::endl;
for (carIndex = garage.begin();
carIndex != garage.end();
++carIndex )
{
std::cout << " " << carIndex->getPlateNumber() << ", Date In: " <<
carIndex->getDateIn() << ", " << "Time In: " << carIndex->getTimeIn() << "Description:
" << carIndex->getDesc() << std::endl;
}
}
The error I get from the compiler is this:
xmemory(208): error C2664: 'Car::Car(const Car &)' : cannot convert parameter 1 from 'Car *' to 'const Car &'
Reason: cannot convert from 'Car *' to 'const Car'
No constructor could take the source type, or constructor overload resolution was ambiguous
I'm not sure where I'm going wrong, would some please point out how my overload is incorrect?
Thanks
The error is likely the g.insert(currentCar) line in the carEnters method, as g is a std::set<Car>, not a std::set<Car*>. Either pass in a reference to the current car (*currentCar) or make the garage contain pointers to cars.
In addition, you may wish to pass in g as a reference, in the form of...
void carEnters(std::set<Car>& g) { }
void carLeaves(std::set<Car>& g) { }
Otherwise the set is being copied and you might not get the results you want.
If you need explanation as to the why for any of these, add a comment. I used to do some TAing back in the day. :)
I believe #James is on the right track, but passing *CurrentCar isn't really the right answer (at least IMO). Instead, you should back up a bit:
Car *currentCar = new Car ;
Perhaps you have prior experience with Java (or something similar) where this is a routine, normal type of code to write. In C++, however, using new directly is (or at least should be) fairly unusual. What you almost certainly want instead is:
Car currentCar;
and then you'll fill in the fields like:
currentCar.whatever = x;
Then, when you put your currentCar into the std::set (or whatever) you won't have to dereference anything, because you'll be starting with a Car object, which is what's expected. As an aside, I'd note that when you look up the car, you're also creating a Car object dynamically -- but you never seem to delete either one, so you're code is leaking memory.
Edit: I should add that there are alternatives that may be preferable. Right now, you're basically treating a Car as "dumb data", with outside code to operate on that data. If you want your code to be "object oriented", it would almost certainly be better to move the code for reading a Car's data into the class itself, so outside code would just invoke that member function.
Another possibility would be to make a Car an immutable object. Instead of creating an unitialized car, and then setting the appropriate values in that object, I'd pass the correct values to Car's constructor, and eliminate the member functions you currently have for changing those values. At least for your purposes, it doesn't appear that you need to actually change a car's plate number -- it should apparently only ever have one plate number, in which case it would be better for your code to reflect (and enforce) that directly.
Your problem is that your set takes elements of type Car but you are inserting elements of type Car*:
void carEnters( std::set<Car> g)
{
...
Car *currentCar = new Car;
...
g.insert(currentCar);
In this case, currentCar is a pointer to a Car and g.insert expects a Car. There are multiple ways of fixing this - you can change your set to use Car* although your overloaded operator< will no longer work (you'll have to create a functor that is passed to the set and takes two Car*s). You can change currentCar to be of type Car. This results in a bunch of copying however. Or you can ditch currentCar entirely and make a constructor that will set all the variables you need set:
Car(const std::string &plate, const std::string &desc)
{
plateNumber = plate;
description = desc;
setTimeDateIn();
};
then you can just do this:
g.insert(Car(desc, plate));
Which is actually preferable to what you are doing now, as someone might forget to call setTimeDateIn. It makes more sense for that to be called when the Car is constructed.