函数指针（习题课后答案）

 1 #include <stdio.h>

 2 #include <stdlib.h>

 3 #include <ctype.h>

 4 

 5 int is_not_print( int ch )

 6 {

 7     return !isprint( ch );

 8 }

 9 

10 static int(*test_func[])( int ) = {

11     iscntrl,

12     isspace,

13     isdigit,

14     islower,

15     isupper,

16     ispunct,

17     is_not_print

18 };

19 #define N_CATEGORIES ( sizeof( test_func ) / sizeof( test_func[0] ) )

20 

21 char* label[] = {

22     "control",

23     "whitespace",

24     "digit",

25     "lower case",

26     "upper case",

27     "punctuation",

28     "non-printable"

29 };

30 

31 int count[ N_CATEGORIES ];

32 int total;

33 

34 int main()

35 {

36     int ch;

37     int category;

38 

39     while( (ch = getchar()) != EOF )

40     {

41         total += 1;

42         for( category = 0; category < N_CATEGORIES; category += 1 )

43             if( test_func[ category ]( ch ) )

44                 count[ category ] += 1;

45     }

46 

47     if( total == 0 )

48         printf( "No characters in the input!\n" );

49     else

50     {

51         for( category = 0; category < N_CATEGORIES; category += 1 )

52         {

53             printf( "%3.0f%% %s characters\n", count[ category ] * 100.0 / total, label[ category ] );

54         }

55     }

56     return EXIT_SUCCESS;

57 }

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