Getting started with the basics of programming exercises_4
2024-10-08 02:49:19
1、编写一个删除C语言程序中所有的注释语句的程序。要正确处理带引号的字符串与字符串常量，C语言中程序注释不允许嵌套。
#include<stdio.h>
void rcomment(int c);
void in_comment(void);
void echo_quote(int c);
// remove all comments from a valic C program
int main(void)
{
int c;
while((c = getchar()) != EOF)
rcomment(c); return 0;
}
// rcomment: read each character,remove the comments
void rcomment(int c)
{
int d; if(c == '/')
if((d = getchar()) == '*')
in_comment(); // beginning comment
else if(d == '/')
{
putchar(c); // another slash
rcomment(d);
}
else
{
putchar(c); // not a comment
putchar(d);
}
else if(c == '\'' || c == '"')
echo_quote(c); // quote begins
else
putchar(c); // not a comment
}
// in_comment: inside of a valid comment
void in_comment(void)
{
int c, d; c = getchar(); // prev character
d = getchar(); // curr character
while(c != '*' || d != '/') // here can be more readable
{
c = d;
d = getchar();
}
}
// echo_quote: echo characters within quotes
void echo_quote(int c)
{
int d; putchar(c);
while((d = getchar()) != c) // search for end
{
putchar(d);
if(d == '\\')
putchar(getchar()); // ignore escape seq
}
}
2、小型词法分析器
编写程序，查找C语言程序中的基本语法错误，如圆括号、方括号以及花括号不配对等。要正确处理引号（包括单引号、双引号）、转义字符序列与注释。
#include<stdio.h>
int brace, brack, paren;
void in_quote(int c);
void in_comment(void);
void search(int c);
// rudimentary syntax checker for C programs
int main(void)
{
int c;
extern int brace, brack, paren;
while((c = getchar()) != EOF)
{
if(c == '/')
{
if((c = getchar()) == '*')
in_comment(); // inside comment
else
search(c);
}
else if(c == '\'' || c == '"')
in_quote(c); // inside quote
else
search(c); if(brace < 0) // output errors
{
printf("Unbalanced braces\n");
brace = 0;
}
else if(brack < 0)
{
printf("Unbalanced brackets\n");
brack = 0;
}
else if (paren < 0)
{
printf("Unbalanced parentheses\n");
}
} if(brace > 0) // output errors
printf("Unbalanced braces\n");
if(brack > 0)
printf("Unbalanced brackets\n");
if(paren > 0)
printf("Unbalanced parentheses\n"); return 0;
} // search: search for rudimentary syntax errors
void search(int c)
{
extern int brace, brack, paren; if(c == '{')
++brace;
else if(c == '}')
--brace;
else if(c == '[')
++brack;
else if(c == ']')
--brack;
else if(c == '(')
++paren;
else if(c == ')')
--paren;
} // in_comment: inside of a valid comment
void in_comment(void)
{
int c, d; c = getchar(); // pre character
d = getchar(); // curr character
while(c != '*' || d != '/')
{
c = d;
d = getchar();
}
} // in_quote: inside quote
void in_quote(int c)
{
int d; while((d = getchar()) != c) // search end quote
if(d == '\\')
getchar(); // ignore escape seq
}
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