dele-rem.cpp

dele-rem：《编译原理》词法分析器中一个很精典的错误处理子程序

#include"stdio.h"
#include"stdlib.h"

void main()
{
	FILE *fp1,*fp2;
	char ch1,ch2;
	if((fp1=fopen("d:\\abc\\input.txt","r"))==NULL)
	{
		printf("file cannot be opened\n");
		exit(0);
	}
		if((fp2=fopen("d:\\abc\\middle.txt","w"))==NULL)
	{
		printf("file cannot be writed\n");
		exit(0);
	}
	ch1=fgetc(fp1);
    ch2=fgetc(fp1);
 	while(!feof(fp1))
	{
		if (ch1=='/')
		{
			if(ch2=='/')
			   while((ch2=fgetc(fp1))!=10);  //read only not write
			else
			{
				if (ch2=='*')
				{
					while(!(ch1=='*' && ch2=='/')) //去掉/*...*/注释
					{ch1=ch2;ch2=fgetc(fp1);}
                    ch2=fgetc(fp1);
                }
				else
                    fputc(ch1,fp2);
			}
        }
		else
		    fputc(ch1,fp2);
		ch1=ch2;
		ch2=fgetc(fp1);
		printf("%c",ch2);
	}
	fputc(ch1,fp2);
	fclose(fp1);
	fclose(fp2);
}