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(一)

　　《写给大家看的C语言书(第2版)》是邮电社图灵公司引进翻译的一本C语言入门书，这是一本垃圾书。搞不清图灵为什么引进了这样一本垃圾书。该书作者基本不懂得C编程技术，书中误导、错谬比比皆是。
　　该书的附录B给出了一个21点游戏的代码，这是一个很糟糕的C程序，毛病很多，实在不足以为初学者以示范，当反面教材还差不多。考虑到其中的很多毛病初学者也有，所以拿来在此评析一番。
　　首先，这段程序可读性极差，甚至可以说是乱作一团。连我这种阅读代码能力很强的人看起来都很费劲，初学者根本就没有可能看懂。
　　乱作一团和可读性还不是一回事。可读性指的是代码晦涩难懂，乱作一团则是指不顾起码的编程规范。譬如代码没有基本的缩进

do {
ans = getAns("Hit or stand (H/S)?");
if ( ans = 'H' )
{ playerGetsCard(&numCards,cards,
playerPoints);
}  
}while(ans != 'S' );

任意地截断语句或声明

do { initCardsScreen(cards,playerPoints,dealerPoints,
total, &numCards);
dealerGetsCard(&numCards,cards, dealerPoints);

　　代码本来就够乱的了，又塞进了一大堆更乱更不规范的注释。这些注释其实是应该翻译过来的，但是很可惜译者偷懒并没有翻译，对于国内初学者来说，这就更加混乱。混乱的代码和混乱的注释纠结在一起，整个源程序惨不忍睹。

　　为了不折磨大家眼球，下面以删除了注释的代码为基础评析。大家也可以顺便比较一下（http://ishare.iask.sina.com.cn/f/20886221.html），看看这些注释是不是起了很坏的作用。如果感觉这里删除了注释的代码更清楚一些，那么无疑原书上的注释是垃圾。

#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 = 0;


void dispTitle(void);
void initCardsScreen(int cards[52],int playerPoints[2],
int dealerPoints[2], int total[2], 
int *numCards);
int dealCard(int * numCards,int cards[52]);
void dispCard(int cardDrawn,int points[2]);
void totalIt(int points[2],int tatal[2],int who);
void dealerGetsCard(int *numCards,int cards[52],
int dealerPoints[2]);
void playerGetsCard(int *numCards,int cards[52],
int playerPoints[2]);
char getAns(char mesg[]);
void findWinner(int total[2]);

main()
{
int numCards;
int cards[52],playerPoints[2],dealerPoints[2],total[2];
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] < 17 );
totalIt(dealerPoints,total,DEALER);
findWinner(total); 
ans=getAns("\nPlay again(Y/N)?");  

}while(ans=='Y');

return ;

}
void initCardsScreen(int cards[52],int playerPoints[2],
int dealerPoints[2], int total[2], 
int *numCards)
{
int sub,val = 1 ;
char firstName[15];
*numCards=52;

for(sub=0;sub<=51;sub++){
val = (val == 14) ? 1 : val;
cards[sub] = val;
val++;  }
for(sub=0;sub<=1;sub++)
{ playerPoints[sub]=dealerPoints[sub]=total[sub]=0;}
dispTitle();
if (askedForName==0)
{ printf("What is your first name?");
scanf(" %s",firstName);
askedForName=1;
printf("Ok, %s,get ready for casino action!\n\n",
        firstName);
getchar();
}
return;        
}

void playerGetsCard(int *numCards,int cards[52],
int playerPoints[2])
{
int newCard;
newCard = dealCard(numCards, cards);
printf("You draw:");
dispCard(newCard,playerPoints);
}
void dealerGetsCard(int *numCards,int cards[52],
int dealerPoints[2])
{
int newCard;
newCard = dealCard(numCards,cards);
printf("The dealer draws:");
dispCard(newCard,dealerPoints);
}
int dealCard(int * numCards,int cards[52])
{
int cardDrawn,subDraw;
time_t t;
srand(time(&t));
subDraw = (rand()%(*numCards));
cardDrawn = cards[subDraw];
cards[subDraw] = cards[*numCards -1];
(*numCards)-;
return cardDrawn;
}
void dispCard(int cardDrawn, int points[2])
{
switch(cardDrawn){
case(11): printf("%s\n","Jack");
points[ACELOW] += 10;
points[ACEHIGH] += 10;
break;
case(12): printf("%s\n","Queen");
points[ACELOW] += 10;
points[ACEHIGH] += 10;
break;
case(13): printf("%s\n","King");
points[ACELOW] += 10;
points[ACEHIGH] += 10;
break;
default : points[ACELOW] += cardDrawn;
if(cardDrawn==1)
{ printf("%s\n","Ace");
  points[ACEHIGH]+= 11;
}
else
{  points[ACEHIGH]+=cardDrawn;
   printf("%d\n",cardDrawn); }
}
return ;
}
void totalIt(int points[2],int total[2],int who)
{
if ((points[ACELOW] == points[ACEHIGH])||
(points[ACEHIGH] > 21 ))
{ 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[2])
{
if ( total[DEALER] ==  21 )
{ printf("The house wins.\n");
  return ;}
if ( (total[DEALER] > 21) && (total[PLAYER] > 21))
{ printf("%s", "Nobody wins.\n");
  return ; }
if ((total[DEALER] >= total[PLAYER])&& (total[DEALER] < 21))
{ 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 = 0 ;
while(i<25)
{ printf("\n");
i++; }
printf("\n\n*Step right up to the Blackjack tables*\n\n");
return ;
}

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