Please check my C++

**laserlight** · 07-10-2008

Only if enum's are the same size as int's, which not all compilers will always do

The C++ Standard makes it clear that "it is implementation-defined which integral type is used as the underlying type for an enumeration except that the underlying type shall not be larger than int unless the value of an enumerator cannot fit in an int or unsigned int."

**csonx_p** · 07-10-2008

How do i pass stdout to ofstream in C++... In C

Code:

foo(stdout);
.....
.....

foo(FILE *fs)
{
   fprintf(fs, "sdfdsf"); // go to screen
}

**matsp** · 07-10-2008

So you pass a reference of an fstream, like you do in the operator >> and operator << overloads.

Then you call foo(cout) for example.

--
Mats

**matsp** · 07-10-2008

Originally Posted by laserlight

The C++ Standard makes it clear that "it is implementation-defined which integral type is used as the underlying type for an enumeration except that the underlying type shall not be larger than int unless the value of an enumerator cannot fit in an int or unsigned int."

So, clearly

Code:

enum e { a, b, c};

can fit in one byte, whilst

Code:

enum e { a, b, c = 256};

would take up at least two bytes.

Sure, most compilers make it a 32-bit int. Some have switches to say which size it should use. In other cases, it's entirely up to the compiler.

If you ever cast pointers or references to enum's to pointer or reference to int, then you should have an assert or similar to detect compilers that doesn't fulfill your expectations.

--
Mats

**csonx_p** · 07-10-2008

Originally Posted by matsp

So you pass a reference of an fstream, like you do in the operator >> and operator << overloads.

Then you call foo(cout) for example.

--
Mats

Are you saying i must overload ifstream? Not clear....

Code:

void Car::read(ifstream& fin, bool isKeyboard)
{
	char make_temp[15], model_temp[15];

	if(isKeyboard)	// Get record from keyboard
	{	
		fin >> make_temp >> model_temp;
		fin >> yearModel;
		fin >> engineCapacity;
		fin >> returnDate.day >> returnDate.month >> returnDate.year;
		fin >> tankStatus;
		make = make_temp;
		model = model_temp;
        }
}

I may use this function for two purposes, reading from file or keyboard...
what do i pass to it when calling it if reading from keyboard?

**laserlight** · 07-10-2008

Are you saying i must overload ifstream?

Typically we would overload for std::istream instead since std::ifstream is-a std::istream.

what do i pass to it when calling it if reading from keyboard?

std::cin, but you need to overload for std::istream, not std::ifstream.

**matsp** · 07-10-2008

Originally Posted by csonx_p

I may use this function for two purposes, reading from file or keyboard...
what do i pass to it when calling it if reading from keyboard?

Code:

car::read(cin, true);

--
Mats

**csonx_p** · 07-10-2008

Originally Posted by matsp

Code:

car::read(cin, true);

--
Mats

Mats, cin is "istream", but function expects "ifstream", i've change all the ifstreams to istreams, since istream is a base class of ifstream, not other way around.. Compiles happily

**matsp** · 07-10-2008

Yes, sorry about that "f" in ifstream, I did mean istream - just got myself a bit carried away, I think...

--
Mats

**Elysia** · 07-10-2008

Note that your << and >> operators render the read and write members useless.
Why? Because you can do this:

std::ofstream out("my file.txt");
Car car;
out << car;
std::ifstream in("my file.txt");
in >> car;

It doesn't matter if it's the keyboard of a file, because both derive from std::i/ostream, it works. It's a good example of polymorphism.

**csonx_p** · 07-10-2008

Originally Posted by Elysia

Note that your << and >> operators render the read and write members useless.
Why? Because you can do this:

std::ofstream out("my file.txt");
Car car;
out << car;
std::ifstream in("my file.txt");
in >> car;

It doesn't matter if it's the keyboard of a file, because both derive from std::i/ostream, it works. It's a good example of polymorphism.

Interesting this!!! hmm... will test it, thnx

**csonx_p** · 07-10-2008

Ehm... is fflush(stdout) similar cout.clear() ... ?

**Elysia** · 07-10-2008

Nope, it's equalient to
cout.flush();

**csonx_p** · 07-10-2008

Originally Posted by Elysia

Nope, it's equalient to
cout.flush();

Ok, let me not bit around the bush... In my programming experience i've been flushing the stdin using fflush(), which i've learned is illegal, but work nonetheless... Suggestions are people should use getchar() to clear unwanted characters on stdin... So, just now i tried cin.flush() & doesn't exist... Guess was trying my luck... Is there a C++ way of doing this?