1.13.2. Arithmetic

1.13.2. Arithmetic
	1.13. C++ Simple Types

[ fromfile: arithmetic.xml id: arithmetic ]

For each of its native numerical types, C++ provides these four basic arithmetic operators:
- addition (+)
- subtraction (-)
- multiplication (*)
- division (/)
These operator symbols are used to form expressions in the standard infix syntax that you learned in math class.

C++ provides shortcut operators that combine each of the basic operators with the assignment operator (=) so that, for example, it is possible to write
```
 x += y; 
```
instead of
```
 x = x + y; 
```

C++ also provides unary increment (++) and decrement (--) operators that can be used with integral types.
If one of these operators is applied to a variable on its left side (prefix), then the operation is performed before the rest of the expression is evaluated.
If it is applied to a variable on its right side (postfix), then the operation is performed after the rest of the expression is evaluated.
Prefix operators are recommended over postfix operators when it doesn't matter whether the operation takes place before or after the expression is evaluated.

Example 1.21. src/arithmetic/arithmetic.cpp

[ . . . . ]

#include <QTextStream>

int main() {
    QTextStream cout(stdout);
    double x(1.23), y(4.56), z(7.89) ;
    int i(2), j(5), k(7);
    x += y ;
    z *= x ;
    cout << "x = " << x << "\tz = " << z
            << "\nx - z = " << x - z << endl ;

The result of dividing one int by another produces an int quotient and an int remainder.
The operator / is used to obtain the quotient.
The operator % (called the modulus operator) is used to obtain the remainder.
Example 1.22 demonstrates the use of these integer arithmetic operators.

Example 1.22. src/arithmetic/arithmetic.cpp

[ . . . . ]

    cout << "k / i = " << k / i 
            << "\tk % j = " << k % j << endl ;
    cout << "i = " << i << "\tj = " << j << "\tk = " << k << endl;
    cout << "++k / i = " << ++k / i << endl;
    cout << "i = " << i << "\tj = " << j << "\tk = " << k << endl;
    cout << "i * j-- = " << i * j-- << endl;
    cout << "i = " << i << "\tj = " << j << "\tk = " << k << endl;

Mixed expressions, if valid, generally produce results of the widest of the argument types.^[10]

Example 1.23. src/arithmetic/arithmetic.cpp

[ . . . . ]

    cout << "z / j = " << z / j << endl ;

C++ also provides a full set of boolean operators to compare numeric expressions.
A bool expression can be negated with the unary not (!) operator.
Expressions can be formed with two or more bool expressions using the conjunction and disjunction operators
- and (&&)
- or (||)

Example 1.24. src/arithmetic/arithmetic.cpp

[ . . . . ]

    /*   if () ... else   approach */
    if (x * j <= z)
        cout << x * j << " <= " << z << endl ;
    else
        cout << x * j << " > " << z << endl;

```
(boolExpr) ? expr1 : expr2
```
returns expr1 if boolExpr is true, and otherwise returns expr2.

Example 1.25. src/arithmetic/arithmetic.cpp

[ . . . . ]

    /* conditional operator approach */
    cout << x * k
            <<( (x * k < y * j) ? " < " : " >= ")
            << y * j << endl;
    return 0;
}

Example 1.26 shows the output of this program.

Example 1.26. src/arithmetic/arithmetic.cpp

[ . . . . ]

Output:

x = 5.79        z = 45.6831
x - z = -39.8931
k / i = 3       k % j = 2
i = 2   j = 5   k = 7
++k / i = 4
i = 2   j = 5   k = 8
i * j-- = 10
i = 2   j = 4   k = 8
z / j = 11.4208
23.16 <= 45.6831
46.32 >= 18.24

^[10]See Table 1.2 for relative type widths.


1.13.1. `main`, and Command-Line Arguments		1.13.3. Exercises: C++ Simple Types