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（六）

. #include <stdio.h>
. #include <time.h>
. #include <ctype.h>
. #include <stdlib.h>
.
. #define BELL '\a'
. #define DEALER 0
. #define PLAYER 1
.
. #define ACELOW 0
. #define ACEHIGH 1
.
. int askedForName = ;
.
.
. void dispTitle(void);
. void initCardsScreen(int cards[],int playerPoints[],
. int dealerPoints[], int total[],
. int *numCards);
. int dealCard(int * numCards,int cards[]);
. void dispCard(int cardDrawn,int points[]);
. void totalIt(int points[],int tatal[],int who);
. void dealerGetsCard(int *numCards,int cards[],
. int dealerPoints[]);
. void playerGetsCard(int *numCards,int cards[],
. int playerPoints[]);
. char getAns(char mesg[]);
. void findWinner(int total[]);
.
. main()
. {
.    int numCards;
.    int cards[],playerPoints[],dealerPoints[],total[];
.    char ans;
.
.    do
.    {
.       initCardsScreen(cards,playerPoints,dealerPoints,total, &numCards);
.       dealerGetsCard(&numCards,cards, dealerPoints);
.       printf("\n");
.       playerGetsCard(&numCards,cards,playerPoints);
.       playerGetsCard(&numCards,cards,playerPoints);
.       do
.       {
.          ans = getAns("Hit or stand (H/S)?");
.          if ( ans == 'H' )
.          {
.             playerGetsCard(&numCards,cards,playerPoints);
.          }
.       }
.       while( ans != 'S' );
.
.       totalIt(playerPoints,total,PLAYER);
.       do
.       {
.          dealerGetsCard(&numCards,cards,dealerPoints);
.       }
.       while (dealerPoints[ACEHIGH] <  );
.
.       totalIt(dealerPoints,total,DEALER);
.       findWinner(total);
.
.       ans = getAns("\nPlay again(Y/N)?");
.    }
.    while(ans=='Y');
.
.    return ;
. }
.
. void initCardsScreen( int cards[],int playerPoints[],
.                       int dealerPoints[], int total[],
.                       int *numCards )
. {
.    int sub,val =  ;
.    char firstName[];
.    *numCards=;
.
.    for(sub=;sub<=;sub++)
.    {
.       val = (val == ) ?  : val;
.       cards[sub] = val;
.       val++;
.    }
.
.    for(sub=;sub<=;sub++)
.    {
.       playerPoints[sub]=dealerPoints[sub]=total[sub]=;
.    }
.    dispTitle();
.
.    if (askedForName==)
.    {
.       printf("What is your first name?");
.       scanf(" %s",firstName);
.       askedForName=;
.       printf("Ok, %s,get ready for casino action!\n\n",firstName);
.       getchar();
.    }
.    return;
. }
.
. void playerGetsCard(int *numCards,int cards[],int playerPoints[])
. {
.    int newCard;
.    newCard = dealCard(numCards, cards);
.    printf("You draw:");
.    dispCard(newCard,playerPoints);
. }
.
.
. void dealerGetsCard(int *numCards,int cards[],int dealerPoints[])
. {
.    int newCard;
.    newCard = dealCard(numCards,cards);
.    printf("The dealer draws:");
.    dispCard(newCard,dealerPoints);
. }
.
. int dealCard(int * numCards,int cards[])
. {
.    int cardDrawn,subDraw;
.    time_t t;
.    srand(time(&t));
.    subDraw = (rand()%(*numCards));
.    cardDrawn = cards[subDraw];
.    cards[subDraw] = cards[*numCards -];
.    (*numCards)--;
.    return cardDrawn;
. }
.
. void dispCard(int cardDrawn, int points[])
. {
.    switch(cardDrawn)
.    {
.       case(): printf("%s\n","Jack");
.                 points[ACELOW] += ;
.                 points[ACEHIGH] += ;
.                 break;
.       case(): printf("%s\n","Queen");
.                 points[ACELOW] += ;
.                 points[ACEHIGH] += ;
.                 break;
.       case(): printf("%s\n","King");
.                 points[ACELOW] += ;
.                 points[ACEHIGH] += ;
.                 break;
.       default : points[ACELOW] += cardDrawn;
.                 if(cardDrawn==)
.                 {
.                    printf("%s\n","Ace");
.                    points[ACEHIGH]+= ;
.                 }
.                 else
.                 {
.                   points[ACEHIGH]+=cardDrawn;
.                   printf("%d\n",cardDrawn);
.                 }
.    }
.    return ;
. }
.
. void totalIt(int points[],int total[],int who)
. {
.    if ( (points[ACELOW] == points[ACEHIGH])
.       ||(points[ACEHIGH] <  ))
.    {
.      total[who] = points[ACELOW];
.    }
.    else
.    {
.        total[who] = points[ACEHIGH];
.    }
.
.    if (who == PLAYER )
.    {
.       printf("You have a total of %d\n\n", total[PLAYER]);
.    }
.    else
.    {
.        printf("The house stands with a total of %d\n\n",
.        total[DEALER]);
.    }
.    return;
. }
.
. void findWinner(int total[])
. {
.    if ( total[DEALER] ==   )
.    {
.        printf("The house wins.\n");
.        return ;
.    }
.    if ( (total[DEALER] > ) && (total[PLAYER] > ) )
.    {
.       printf("%s", "Nobody wins.\n");
.       return ;
.    }
.    if ((total[DEALER] >= total[PLAYER])&& (total[DEALER] < ))
.    {
.       printf("The house wins.\n");
.       return ;
.    }
.    printf("%s%c","You win!\n",BELL);
.    return;
. }
.
. char getAns(char mesg[])
. {
.    char ans;
.    printf("%s", mesg);
.    ans = getchar();
.    getchar();
.    return toupper(ans);
. }
.
. void dispTitle(void)
. {
.    int i =  ;
.    while(i<)
.    {
.         printf("\n");
.         i++;
.    }
.    printf("\n\n*Step right up to the Blackjack tables*\n\n");
.    return ;
. }

　　main()函数中player完成抽牌之后，立刻计算了player的点数：

.       totalIt(playerPoints,total,PLAYER);

　　这个计算结果基于ACE的点数被作为1或11两种可能性，取最好一种作为最后的结果。

. void totalIt(int points[],int total[],int who)
. {
.    if ( (points[ACELOW] == points[ACEHIGH])
.       ||(points[ACEHIGH]  >   ))
.    {
.      total[who] = points[ACELOW];
.    }
.    else
.    {
.        total[who] = points[ACEHIGH];
.    }
.
.    if (who == PLAYER )
.    {
.       printf("You have a total of %d\n\n", total[PLAYER]);
.    }
.    else
.    {
.        printf("The house stands with a total of %d\n\n",
.        total[DEALER]);
.    }
.    return;
. }

　　这个函数让我们得以领略什么叫思路含糊和废话连篇。首先

.    if ( (points[ACELOW] == points[ACEHIGH])
.       ||(points[ACEHIGH]  >   ))
.    {
.      total[who] = points[ACELOW];
.    }
.    else
.    {
.        total[who] = points[ACEHIGH];
.    }

　　它的意思是当较高点数超过21点时把较低作为最终的点数，否则把较高点数作为最后的点数。显而易见这可以更简洁地表述为

      if ( points[ACEHIGH] > 21 )
      {
         total[who] = points[ACELOW];
      }
      else
      {
         total[who] = points[ACEHIGH];
      }

　　原来的代码把“(points[ACELOW] == points[ACEHIGH])||”写出来是思路不清导致的拖泥带水。

　　更简洁的写法是：

total[who] = ( points[ACEHIGH] > 21 )? points[ACELOW]: points[ACEHIGH];

　　“?:”这个三目运算在这里应用得恰到好处。

　　有些人对三目运算有一种无名的恐惧，鼓吹所谓“尽量不要用三目运算符”。这是毫无道理的，这种无理源自无知。他们自己不会用刀，于是就骗人骗己地宣称使用木棍强于用刀。

.    if (who == PLAYER )
.    {
.       printf("You have a total of %d\n\n", total[PLAYER]);
.    }
.    else
.    {
.        printf("The house stands with a total of %d\n\n",
.        total[DEALER]);
.    }

　　这一段同样拖泥带水，其实它的效果和下面写法没有本质区别：

   printf( "%s a total of %d\n\n",
           who == PLAYER ? "You have" : "The house stands with",
           total[who] );

　　所以totalIt()函数应改写为

      void totalIt(int [],int [],int );

      void totalIt(int points[],int total[],int who)
      {

         total[who] = ( points[ACEHIGH] > 21 )? points[ACELOW]: points[ACEHIGH];

         printf( "%s a total of %d\n\n",
                 who == PLAYER ? "You have" : "The house stands with",
                 total[who] );

      }

　　计算了完player的点数之后，按照规则在main()中由dealer继续抽牌（前面已抽过第一张牌）。dealer抽牌的策略是不到17点则继续，据代码作者说现实中的庄家的策略也是如此。

.       do
.       {
.          dealerGetsCard(&numCards,cards,dealerPoints);
.       }
.       while ( dealerPoints[ACEHIGH] <  );

　　dealerGetsCard ()函数的功能与playerGetsCard()函数重叠，前面已经提到过，甚至可以说这两个函数都是多余的。

　　此外这里还有一个更严重的问题，那就是“dealerPoints[ACEHIGH] < 17”这个表达式的逻辑问题。这个表达式要求dealer的点数达到17点或以上时停止抽牌，但问题在于点数有两种计算方法，一种是把Ace作为11点（Soft hand），另一种是把Ace作为1点。“dealerPoints[ACEHIGH] ”的意义是Soft hand点数，但是原作者在对程序的说明中压根就没有明确dealer的Soft hand点数达到或超过17点时停牌，只是泛泛地说了一句“the dealer stands on 17”。按软件工程的说法，这叫需求不清，是比代码错误更加严重的错误。

　　紧接着，矛盾出现了。

.       totalIt(dealerPoints,total,DEALER);

　　totalIt()函数计算dealer的点数却是按照最好成绩计算的，这就发生了矛盾。比如dealer为15点时又取了一张牌Ace，按照Soft hand规则，dealer的点数是25点，但最后的成绩却是按照硬牌规则为16点，而如果dealer的点数为16点，那么前面他根本就不应该停牌。这是“双重标准”的C语言版。

　　这里较为合理的写法应该是

       do
       {
          dealerGetsCard(&numCards,cards,dealerPoints);
             totalIt(dealerPoints,total,DEALER);
       }
       while ( total [DEALER] < 17 );