Shorthand Assignments

There is a variation on the assignment statement, sometimes referred to as a shorthand

assignment, that simplifies the coding of a certain type of assignment operation. For

example,

x = x+10;

can be written as

x += 10;

The operator += tells the compiler to assign to x the value of x plus 10.

This shorthand works for all the binary operators (those that require two

operands). In general, statements like:

var = var operator expression

can be rewritten as

var operator = expression

For another example,

x = x-100;

is the same as

x -= 100;

Shorthand notation is widely used in professionally written C/C++ programs; you

should become familiar with it.

Type Casts in C C++

You can force an expression to be of a specific type by using a cast. The general form of
a cast is
(type) expression
where type is a valid data type. For example, to make sure that the expression x/2
evaluates to type float, write
(float) x/2

Casts are technically operators. As an operator, a cast is unary and has the same
precedence as any other unary operator.
Although casts are not usually used a great deal in programming, they can be very
useful when needed. For example, suppose you wish to use an integer for loop control,
yet to perform computation on it requires a fractional part, as in the following
program:
#include <stdio.h>
int main(void) /* print i and i/2 with fractions */
{
int i;
for(i=1; i<=100; ++i)
printf("%d / 2 is: %f\n", i, (float) i /2);
return 0;
}
Without the cast (float), only an integer division would have been performed. The cast
ensures that the fractional part of the answer is displayed.

The [ ] and ( ) Operators

Parentheses are operators that increase the precedence of the operations inside them.
Square brackets perform array indexing (arrays are discussed fully in Chapter 4).
Given an array, the expression within square brackets provides an index into that
array. For example,
#include <stdio.h>
char s[80];
int main(void)
{
s[3] = 'X';
printf("%c", s[3]);
return 0;
}
first assigns the value 'X' to the fourth element (remember, all arrays begin at 0) of
array s, and then prints that element.

The ? Operator Conditional or ternary operator

C/C++ contains a very powerful and convenient operator that replaces certain
statements of the if-then-else form. The ternary operator ? takes the general form
Exp1 ? Exp2 : Exp3;
where Exp1, Exp2, and Exp3 are expressions. Notice the use and placement of the colon.
The ? operator works like this: Exp1 is evaluated. If it is true, Exp2 is evaluated
and becomes the value of the expression. If Exp1 is false, Exp3 is evaluated and its
value becomes the value of the expression. For example, in
x = 10;
y = x>9 ? 100 : 200;
y is assigned the value 100. If x had been less than 9, y would have received the value
200. The same code written using the if-else statement is
x = 10;
if(x>9) y = 100;
else y = 200;
The ? operator will be discussed more fully in Chapter 3 in relationship to the other
conditional statements.