劣质代码评析——《写给大家看的C语言书(第2版)》附录B之21点程序(二)

　　下面继续分析这个代码。为了便于说明问题，为代码添加了行号。

0. #include <stdio.h>

1. #include <time.h>

2. #include <ctype.h>

3. #include <stdlib.h>

4. 

5. #define BELL '\a'

6. #define DEALER 0

7. #define PLAYER 1

8. 

9. #define ACELOW 0

10. #define ACEHIGH 1

11. 

12. int askedForName = 0;

13. 

14. void dispTitle(void);

15. void initCardsScreen(int cards[52],int playerPoints[2],

16. int dealerPoints[2], int total[2], 

17. int *numCards);

18. int dealCard(int * numCards,int cards[52]);

19. void dispCard(int cardDrawn,int points[2]);

20. void totalIt(int points[2],int tatal[2],int who);

21. void dealerGetsCard(int *numCards,int cards[52],

22. int dealerPoints[2]);

23. void playerGetsCard(int *numCards,int cards[52],

24. int playerPoints[2]);

25. char getAns(char mesg[]);

26. void findWinner(int total[2]);

27. 

28. main()

29. {

30.    int numCards;

31.    int cards[52],playerPoints[2],dealerPoints[2],total[2];

32.    char ans;

33. 

34.    do 

35.    { 

36.       initCardsScreen(cards,playerPoints,dealerPoints,total, &numCards);

37.       dealerGetsCard(&numCards,cards, dealerPoints);

38.       printf("\n");

39.       playerGetsCard(&numCards,cards,playerPoints); 

40.       playerGetsCard(&numCards,cards,playerPoints);

41.       do

42.       {

43.          ans = getAns("Hit or stand (H/S)?");

44.          if ( ans == 'H' )

45.          { 

46.             playerGetsCard(&numCards,cards,playerPoints);

47.          }  

48.       }

49.       while( ans != 'S' );

50. 

51.       totalIt(playerPoints,total,PLAYER);

52.       do

53.       {

54.          dealerGetsCard(&numCards,cards,dealerPoints);

55.       }

56.       while (dealerPoints[ACEHIGH] < 17 );

57. 

58.       totalIt(dealerPoints,total,DEALER);

59.       findWinner(total); 

60. 

61.       ans = getAns("\nPlay again(Y/N)?");  

62.    }

63.    while(ans=='Y');

64. 

65.    return ;

66. 

67. }

68. 

69. void initCardsScreen( int cards[52],int playerPoints[2],

70.                       int dealerPoints[2], int total[2], 

71.                       int *numCards )

72. {

73.    int sub,val = 1 ;

74.    char firstName[15];

75.    *numCards=52;

76. 

77.    for(sub=0;sub<=51;sub++)

78.    {

79.       val = (val == 14) ? 1 : val;

80.       cards[sub] = val;

81.       val++;  

82.    }

83. 

84.    for(sub=0;sub<=1;sub++)

85.    { 

86.       playerPoints[sub]=dealerPoints[sub]=total[sub]=0;

87.    }

88.    dispTitle();

89. 

90.    if (askedForName==0)

91.    { 

92.       printf("What is your first name?");

93.       scanf(" %s",firstName);

94.       askedForName=1;

95.       printf("Ok, %s,get ready for casino action!\n\n",firstName);

96.       getchar();

97.    }

98.    return;        

99. }

100. 

101. void playerGetsCard(int *numCards,int cards[52],int playerPoints[2])

102. {

103.    int newCard;

104.    newCard = dealCard(numCards, cards);

105.    printf("You draw:");

106.    dispCard(newCard,playerPoints);

107. }

108. 

109. 

110. void dealerGetsCard(int *numCards,int cards[52],int dealerPoints[2])

111. {

112.    int newCard;

113.    newCard = dealCard(numCards,cards);

114.    printf("The dealer draws:");

115.    dispCard(newCard,dealerPoints);

116. }

117. 

118. int dealCard(int * numCards,int cards[52])

119. {

120.    int cardDrawn,subDraw;

121.    time_t t;

122.    srand(time(&t));

123.    subDraw = (rand()%(*numCards));

124.    cardDrawn = cards[subDraw];

125.    cards[subDraw] = cards[*numCards -1];

126.    (*numCards)-;

127.    return cardDrawn;

128. }

129. 

130. void dispCard(int cardDrawn, int points[2])

131. {

132.    switch(cardDrawn)

133.    {

134.       case(11): printf("%s\n","Jack");

135.                 points[ACELOW] += 10;

136.                 points[ACEHIGH] += 10;

137.                 break;

138.       case(12): printf("%s\n","Queen");

139.                 points[ACELOW] += 10;

140.                 points[ACEHIGH] += 10;

141.                 break;

142.       case(13): printf("%s\n","King");

143.                 points[ACELOW] += 10;

144.                 points[ACEHIGH] += 10;

145.                 break;

146.       default : points[ACELOW] += cardDrawn;

147.                 if(cardDrawn==1)

148.                 { 

149.                    printf("%s\n","Ace");

150.                    points[ACEHIGH]+= 11;

151.                 }

152.                 else

153.                 {  

154.                   points[ACEHIGH]+=cardDrawn;

155.                   printf("%d\n",cardDrawn); 

156.                 }

157.    }

158.    return ;

159. }

160. 

161. void totalIt(int points[2],int total[2],int who)

162. {

163.    if ( (points[ACELOW] == points[ACEHIGH])

164.       ||(points[ACEHIGH] > 21 ))

165.    { 

166.      total[who] = points[ACELOW];

167.    }

168.    else

169.    { 

170.        total[who] = points[ACEHIGH];

171.    }

172. 

173.    if (who == PLAYER )

174.    {

175.       printf("You have a total of %d\n\n", total[PLAYER]);

176.    }

177.    else

178.    {

179.        printf("The house stands with a total of %d\n\n", 

180.        total[DEALER]);

181.    }

182.    return;

183. }

184. 

185. void findWinner(int total[2])

186. {

187.    if ( total[DEALER] ==  21 )

188.    {

189.        printf("The house wins.\n");

190.        return ;

191.    }

192.    if ( (total[DEALER] > 21) && (total[PLAYER] > 21) )

193.    { 

194.       printf("%s", "Nobody wins.\n");

195.       return ; 

196.    }

197.    if ((total[DEALER] >= total[PLAYER])&& (total[DEALER] < 21))

198.    { 

199.       printf("The house wins.\n");

200.       return ; 

201.    }

202.    if ((total[PLAYER] > 21)&& (total[DEALER] < 21))

203.    { 

204.       printf("The house wins.\n");

205.       return ; 

206.    }

207.    printf("%s%c","You win!\n",BELL);

208.    return;

209. }

210. 

211. char getAns(char mesg[])

212. {

213.    char ans;

214.    printf("%s", mesg);

215.    ans = getchar();

216.    getchar();

217.    return toupper(ans);

218. }

219. 

220. void dispTitle(void)

221. {

222.    int i = 0 ;

223.    while(i<25)

224.    { 

225.         printf("\n");

226.         i++; 

227.    }

228.    printf("\n\n*Step right up to the Blackjack tables*\n\n");

229.    return ;

230. }

View Code

　　首先来看main()函数。

31.    int numCards;

32.    int cards[52],playerPoints[2],dealerPoints[2],total[2];

33.    char ans;

 

　　31.行和32.行是这个程序所处理的基本数据对象，相比之下，33.行定义的变量ans则比蚂蚁（ant）还渺小，比鸡肋还无聊，后面会谈到原因。
　　main()函数主要说了一句话(另一句是老生常谈的return 0;)，是一句do-while语句：

 

35.    do 

36.    { 

        /*……*/

62.       ans = getAns("\nPlay again(Y/N)?");  

63.    }

64.    while(ans=='Y');

 

　　它想实现的意图是在一局游戏结束后，由用户选择结束程序还是继续下一轮游戏。但其实说这句话其实根本用不着那个ans变量，代码可以更简洁地写为：

 

35.    do 

36.    { 

        /*……*/

63.    }

64.    while( getAns("\nPlay again(Y/N)?") == 'Y' ) ;

 

　　解决一个问题可能多种方法，最简洁的那种才是正道。奥卡姆剃刀告诉我们，如无必要，勿增实体。简洁是C语言的一个重要的精神特质。
　　现在不难看出33.行定义的变量是完全多余的了。

(未完待续)