我正在从K＆amp; R书中学习C，在第一章中学习练习1.23，我必须编写一个程序，删除用户输入的一些C代码的所有注释。到目前为止，这是我完成的程序。我能做些什么改进吗？
/**
Tuesday, 10/07/2013
Exercise 1.23
Write a program to remove all comments from a C
program. Don't forget to handle quoted strings
and character constants properly. C comments
don't nest.
**/
#include <stdio.h>
#define MAX_LENGTH 65536
#define NOT_IN_COMMENT 0
#define SINGLE_COMMENT 1
#define MULTI_COMMENT 2
main()
{
char code[MAX_LENGTH]; /* Buffer that stores the inputted code */
int size = 0; /* Length of the inputted code */
int loop; /* Integer used for the for loop */
char c; /* Character to input into */
int status = NOT_IN_COMMENT; /* Are we in a comment? What type? */
int in_string = 0; /* Are we inside of a string constant? */
char last_character; /* Value of the last character */
/* Input all code into the buffer until escape sequence pressed */
while ((c = getchar()) != EOF)
code[size++] = c;
code[size] = '\0';
/* Remove all comments from the code and display results to user */
for (loop = 0; loop < size; loop++) {
char current = code[loop];
if (in_string) {
if (current == '"') in_string = 0;
putchar(current);
}
else {
if (status == NOT_IN_COMMENT) {
if (current == '"') {
putchar(current);
in_string = 1;
continue;
}
if (current == '/' && last_character == '/') status = SINGLE_COMMENT;
else if (current == '*' && last_character == '/') status = MULTI_COMMENT;
else if (current != '/' || (current == '/' && loop < size-1 && !(code[loop+1] == '/' || code[loop+1] == '*'))) putchar(current);
}
else if (status == SINGLE_COMMENT) {
if (current == '\n') {
status = NOT_IN_COMMENT;
putchar('\n');
}
}
else if (status == MULTI_COMMENT) {
if (current == '/' && last_character == '*') status = NOT_IN_COMMENT;
}
}
last_character = current;
}
}
答案 0 :(得分：4)
将你的注释剥离到一个函数中（更有用），并且一次用fgets（）读取一行，last_character是不明确的（它是指最后一个，还是以前的？），这使用了更少的对putchar的调用（ ），每行只有一个printf（可以使用puts），保留你正在做的大部分内容，
#include <stdio.h>
#include <string.h>
#define MAX_LENGTH 65536
#define NOT_IN_COMMENT 0
#define SINGLE_COMMENT 1
#define MULTI_COMMENT 2
int status = NOT_IN_COMMENT; /* Are we in a comment? What type? */
int in_string = 0; /* Are we inside of a string constant? */
char* stripcomments(char* stripped,char* code)
{
int ndx; /* index for code[] */
int ondx; /* index for output[] */
char prevch; /* Value of the previous character */
char ch; /* Character to input into */
/* Remove all comments from the code and display results to user */
for (ndx=ondx=0; ndx < strlen(code); ndx++)
{
char current = code[ndx];
if (in_string) {
if (current == '"') in_string = 0;
stripped[ondx++] = current;
}
else {
if (status == NOT_IN_COMMENT) {
if (current == '"') {
stripped[ondx++] = current;
in_string = 1;
continue;
}
if (current == '/' && prevch == '/') status = SINGLE_COMMENT;
else if (current == '*' && prevch == '/') status = MULTI_COMMENT;
else if (current != '/' || (current == '/' && ndx < strlen(code)-1 && !(code[ndx+1] == '/' || code[ndx+1] == '*'))) stripped[ondx++] = current;
}
else if (status == SINGLE_COMMENT) {
if (current == '\n') {
status = NOT_IN_COMMENT;
stripped[ondx++] = '\n';
}
}
else if (status == MULTI_COMMENT) {
if (current == '/' && prevch == '*') status = NOT_IN_COMMENT;
}
}
prevch = current;
}
stripped[ondx] = '\0';
return(stripped);
}
int main(void)
{
char code[MAX_LENGTH]; /* Buffer that stores the inputted code */
char stripped[MAX_LENGTH];
while( fgets(code,sizeof(code),stdin) )
{
//printf("%s\n",code);
//strip comments...
stripcomments(stripped,code);
if( strlen(stripped) > 0 ) printf("%s",stripped);
}
}
我会留给你删除多余的空白行。
答案 1 :(得分：1)
当您处理引用的字符串时，您应该检测转义引号（\"）。例如"\"/* not a comment */\""是一个有效的字符串，但我认为您的代码会从中间删除错误的注释。
如果你想要真正正确，你还应该处理行继续（在下一行继续以\结尾的行）。为了增加毛羽，你也应该处理三角形。 ??/"是一个转义引号，而一行末尾的??/是一个延续。
代码的样式看起来很不错，虽然main应该更恰当地声明为int main(void)。
答案 2 :(得分：1)
对我来说很好，做得好！
也许可以通过添加一些评论来改进:)作为一个粗略的指南，为每个条件添加一个。你正在评论，但只是在循环内部的多汁部分停了下来。但代码看起来很可读。
有用吗？你测试过了吗？
如果我的字符串包含转义的双引号，那么看起来可能会失败...例如"He said, \"Hello, World!\""。
答案 3 :(得分：0)
//G H PATEL COLLEGE OF ENGINEERING & TECHNOLOGY.
//c program to remove comments from given src.txt file, and write back to dest.txt file.
#include <stdio.h>
int main()
{
FILE *src,*dest;
char ch,pre,line[100];
int nflag,qflag,index;
src=fopen("src.txt","r+");
dest=fopen("dest.txt","w+");
nflag=1;
while(!feof(src))
{
index=0;
for(ch=fgetc(src);ch!=EOF && ch!='\n';)
{
if(ch=='"'&&pre!='\\')
{
qflag=0;
for(;ch!='\n' && qflag==0;)
{
line[index++]=ch;
pre=ch;
ch=fgetc(src);
if(ch=='"'&&pre!='\\')
{
qflag=1;
line[index++]=ch;
pre=ch;
ch=fgetc(src);
break;
}
}
}
else if(ch=='/')
{
pre=ch;
ch=fgetc(src);
if(ch=='/')
{
for(;fgetc(src)!='\n';);
break;
}
if(ch=='*')
{
nflag=1;
for(ch=fgetc(src);nflag==1;)
{
if(ch=='*')
{
pre=ch;
ch=fgetc(src);
if(ch=='/')
{
nflag=0;
}
}
else
{
pre=ch;
ch=fgetc(src);
}
}
}
}
else
{
line[index++]=ch;
pre=ch;
ch=fgetc(src);
}
}
line[index]='\0';
if(index>0)
{
line[index] = '\0';
fprintf(dest,"%s\n",line);
fflush(stdin);
}
}
getch();
fclose(src);
fclose(dest);
return 0;
}
答案 4 :(得分：0)
我喜欢这个帖子包含一个＆＃34;评论脱衣舞娘＆＃34;在将它交给JSON解析器之前的项目中。只有我更喜欢FSM方法。希望我的实现对任何人都是可以理解和有用的：
#include <stdio.h>
#include <string.h>
void strip(int ch, FILE *stream)
{
static enum strip_states {
STRIP_STATE_PUTC = 0,
STRIP_STATE_SINGLE,
STRIP_STATE_MULTI,
STRIP_STATE_STRING,
} state = STRIP_STATE_PUTC;
static char _ch = 0;
static unsigned char _nestlevel = 0;
/* String */
if (state == STRIP_STATE_PUTC &&
ch == '"') {
state = STRIP_STATE_STRING;
} else if (state == STRIP_STATE_STRING &&
ch == '"') {
state = STRIP_STATE_PUTC;
/* Multiline */
} else if (_ch == '/' && ch == '*') {
if (state == STRIP_STATE_PUTC)
state = STRIP_STATE_MULTI;
else if (state == STRIP_STATE_MULTI)
_nestlevel++;
} else if (_ch == '*' && ch == '/') {
if (state == STRIP_STATE_MULTI &&
_nestlevel > 0)
_nestlevel--;
else if (state == STRIP_STATE_MULTI &&
_nestlevel == 0)
state = STRIP_STATE_PUTC;
/* Singleline */
} else if (state == STRIP_STATE_PUTC &&
_ch == '/' && ch == '/') {
state = STRIP_STATE_SINGLE;
} else if (state == STRIP_STATE_SINGLE &&
ch == '\n') {
state = STRIP_STATE_PUTC;
}
/* Put character */
if ((state == STRIP_STATE_PUTC && ch != '/') ||
state == STRIP_STATE_STRING)
fputc(ch, stream);
_ch = ch;
}
int main(void)
{
int ch;
while ((ch = fgetc(stdin)) != EOF)
strip(ch, stdout);
return 0;
}
什么有效：
"xxx // comment" "xxx /* comment\n another comment */ yyy" "xxx /* comment /* nested comment */ end of comment */ yyy 目前尚未实施和测试：
亲切的问候， 杰里
答案 5 :(得分：0)
您可以参考下面的简单代码：
#include<stdio.h>
void main()
{
printf("Hello");
/*--------------------------------------------
------------------Ignored by compiler-------
--------------------------------------------
*/
printf("By");
}
<强> INPUT：
#include<stdio.h>
void main()
{
printf("Hello");
printf("By");
}
<强>输出：
{{1}}