Casting Operands

[yorkcoparamedic]

Using the book Ivor Horton's Beginning Visual C++ 2008.
Chapter 2, pages 76-77 - Rules for Casting Operands
Using Microsoft Visual Studio 2008 Pro

I understand the basic of how this casting works in theory. But I tried to write a program to express this example and make it clearer to myself. And also to practice a little too. But my output is not what it should be. I have to be doing something majorly stupid here. Can someone help explain what I have done wrong?

His example is:

double value(31.0);
int count(16);
float many(2.0f);
char num(4);

value = (value - count)*(count - num) / many + num / many;

Now work out what casts the compiler will apply in the exicution of the statement.

When I work everything out in my head or on paper the result is a double value of 92.0

Here is my problem. I have rewrote this several times to find my fault with no luck.

//Ex2_casting.cpp
//Example of how casting works with mathmatical operations
#include <iostream>
using namespace std;

int main()
{
	double value(31.0);
	int count(16);
	float many(2.0f);
	char num(4);

	value = (value - count)*(count - num) / many + num / many;
	cout << endl << "The answer is: " << value << endl;

	double value2;
	value2 = value - count; //(value - count)
	cout << endl << "double value - int count = double value: " << value2 << endl;

	int value3;
	value3 = count - num; //(count - num)
	cout << endl << "int cout - char num = int value: " << value3 << endl;

	double value4;
	value4 = value2 * value3; //(value - count) * (count - num)
	cout << endl << "double value * int value = double value: " << value4 << endl;

	double value5;
	value5 = value4 / many; //(value - count)*(count - num) / many
	cout << endl << "double value / float num = double value: " << value5 << endl;

	float value6;
	value6 = num / many; // num / many;
	cout << endl << "char num / float many = float value: " << value6 << endl;

	double value7;
	value7 = value5 + value6; //(value - count)*(count - num) / many + num / many
	cout << endl << "double value + float value = double value: " << value7 << endl;

	return 0;
}

My output is:
The answer is: 92 Correct

double value - int count = double value: 76

int cout - char num = int value: 12

double value * int value = double value: 912

double value / float num = double value:

char num / float many = float value: 2

double value + float value = double value: 458

Where did I go wrong? Am I just doing the mathmatical calculations wrong? Or is this an error with my varible choices? Or something else?

[kevinkjt2000]

[code]value = (value - count)*(count - num) / many + num / many; //sets the double value = 92.0
value2 = value - count; // sets double value2 = 92 - 16 = 76
value3 = count - num; // sets int value3 = 16 - 4 = 12
value4 = value2 * value3; // sets double value4 = 76 * 12 = 912
value5 = value4 / many; // sets double value5 = 912 / 2 = 456
//Why did you leave no answer for the output on value5?
value6 = num / many; // sets float value6 = 4 / 2 = 2
value7 = value5 + value6; // sets double value7 = 456 + 2 = 458[\code]

I see in your comment that you have:
(value - count)*(count - num) / many + num / many
Maybe try keeping track of parentheses?
(((value - count)*(count - num)) / many) + (num / many)
(((92 - 16) * (16 - 4)) / 2) + (4 / 2) = ((76 * 12) / 2) + 2 = (912 / 2) + 2 = 456 + 2 = 458

I don't see what you original question is asking that math looks perfect to me.

[yorkcoparamedic]

Thanks for your reply. Yes I agree the math is fine and I should use more parentheses, which I will.

I figured out my error here.

int main()
{
	double value(31.0);
	int count(16);
	float many(2.0f);
	char num(4);

	value = (value - count)*(count - num) / many + num / many;
	cout << endl << "The answer is: " << value << endl;

This part reassign's the inital variable double value(31.0) to 92.0

Then when I was continuing below. I was starting out with 92.0 instead of 31.0

double value2;
	value2 = value - count; //(value - count)
	cout << endl << "double value - int count = double value: " << value2 << endl;

	int value3;
	value3 = count - num; //(count - num)
	cout << endl << "int cout - char num = int value: " << value3 << endl;

	double value4;
	value4 = value2 * value3; //(value - count) * (count - num)
	cout << endl << "double value * int value = double value: " << value4 << endl;

	double value5;
	value5 = value4 / many; //(value - count)*(count - num) / many
	cout << endl << "double value / float num = double value: " << value5 << endl;

	float value6;
	value6 = num / many; // num / many;
	cout << endl << "char num / float many = float value: " << value6 << endl;

	double value7;
	value7 = value5 + value6; //(value - count)*(count - num) / many + num / many
	cout << endl << "double value + float value = double value: " << value7 << endl;

	return 0;
}