Sams Teach Yourself C in 21 Days

As you can see in this listing, there is only one rectangle()declaration and

function being used. This function differs from previous examples by using

default values. The function prototype in line 5 contains values being assigned to each of

the parameters. These values are considered default values.

In line 10, you see that the rectangle()function is called in the normal way with each

of its three parameters being passed. In line 13, however, you see that the draw_char

value has been left off. In the output, you can see that the rectangle is still drawn using

an‘X’. The ‘X’character is the default value set in line 5. In lines 16 and 19, the rectan-

gle function is called again, each time with one less parameter. In each case, the default

parameters are pulled from the prototype in line 5.

When using default values, it is always assumed that the values presented are valid from

the left to the right. For example, using the rectangle()function above, you cannot pass

a display character without passing a width and length. The following would generate

bad results:

rectangle( ‘*’ );

This call to rectangle()uses the ASCII value of ‘*’for the width rather than for the

display character. Using the rectangle()function declared in line 5 of Listing B2.5, the

first parameter of the rectangle function is always the width, the second is always the

length, and the third is the display character. You might believe that the following

rectangle ( , , ‘*’);

would fix this problem; however, this will generate an error. You must pass actual para-

meters.

658 Bonus Day 2

ANALYSIS

You should place values that will probably be defaulted as far to the right in

Tip the argument list as possible.

Inline Functions ............................................................................................

Inline functions are also a feature of C++ that is not available in C. An inline function is

like any other function. The difference lies in how the compiler treats the function. By

declaring a function as inline, you are making a request to the compiler. You are request-

ing that the compiler replace all calls to the inline function with a copy of the code

within the inline function.

Inline functions are used simply for speed. Each time you call a function, a little bit of

time is used to go to and return from the function. By declaring a function as inline, you

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