Visual C++编译时 expression:stream!=NULL

[Jessica730]

怎么解决

[棉猴]

把完整代码贴出来吧。另外VC++6.0是我的最爱，没有之一

[Jessica730]

#include<stdlib.h> #include<stdio.h> #include<ctype.h> #include<string.h> #include<math.h> #define MAX_KEY_NUMBER 20 #define KEY_WORD_END "waiting for your expanding" #define ID 6 #define INT 7 #define LT 8 #define LE 9 #define EQ 10 #define NE 11 #define GT 12 #define GE 13 #define IS 14 #define PL 15 #define MI 16 #define MU 17 #define DI 18 #define UCON 19 char TOKEN[20]; int lookup(char*); void out(int, char*); void report_error(); void scanner_example(FILE *fp) { char ch; int i,c; ch=fgetc(fp); int checkdot=0; int checke=0; int t; t=fgetc(fp); fseek(fp,-1,1); while(t!=EOF) { if(isalpha(ch)) { TOKEN[0]=ch; ch=fgetc(fp); i=1; while(isalnum(ch)) { TOKEN[i]=ch; i++; ch=fgetc(fp); } TOKEN[i]='\0'; fseek(fp,-1,1); c=lookup(TOKEN); if(c==0) out(ID, TOKEN); else out(c," "); } else if(isdigit(ch)) { TOKEN[0]=ch; ch=fgetc(fp); i=1; while (isdigit(ch)) { TOKEN[i]=ch; i++; ch=fgetc(fp); } TOKEN[i]='\0'; fseek(fp,-1,1); out(INT,TOKEN); } else if(isdigit(ch)) { TOKEN[0]=ch; ch=fgetc(fp); i=1; while(isdigit(ch)||ch=='.'||ch=='E'||ch=='e') { if (ch=='.'){checkdot=1;} else if(ch=='e'||ch=='E') { checke=1; TOKEN[i]=ch; i++; ch=fgetc(fp); if(ch=='+') { TOKEN[i]=ch; i++; ch=fgetc(fp); { TOKEN[i]=ch; i++; ch=fgetc(fp); continue; } } else { TOKEN[i]=ch; i++; ch=fgetc(fp); { TOKEN[i]=ch; i++; ch=fgetc(fp); continue; } } if (ch=='-') { TOKEN[i]=ch; i++; ch=fgetc(fp); { TOKEN[i]=ch; i++; ch=fgetc(fp); continue; } } TOKEN[i]=ch; i++; ch=fgetc(fp); } TOKEN[i]='\0'; fseek(fp,-1,1); if(checkdot==1) { out(UCON,TOKEN); } else if (checke==1) { out(UCON,TOKEN); } else out(INT,TOKEN); } } else switch (ch) { case '<': ch= fgetc(fp); if (ch=='=') out(LE, " "); else if (ch=='>') out(NE, " "); else { fseek(fp,-1,1); TOKEN[i]=ch; i++; ch=fgetc(fp); out(LT," "); } break; case '=': out(EQ," "); break; case ':': ch=fgetc(fp); if(ch=='=') out(IS," "); else { fseek(fp,-1,1); report_error(); } break; case '>': ch=fgetc(fp); if (ch=='=') out(GE, " "); else { fseek(fp,-1,1); out(GT," "); } break; case '+':out(PL," ");break; case '-':out(MI," ");break; case '*':out(MU," ");break; case '/':out(DI," ");break; case '\n': break; case ' ': break; case '\t': break; default: report_error();break; } ch=fgetc(fp); t=fgetc(fp); fseek (fp,-1,1); } return; } char *KeyWordTable[MAX_KEY_NUMBER]={"begin","end","if","then","else",KEY_WORD_END}; int lookup(char *token) { int n= 0; while(strcmp(KeyWordTable[n],KEY_WORD_END)) { if (!strcmp(KeyWordTable[n],token)) { return n+1; break; } n++; } return 0; } void report_error() { printf("error"); } void out(int c, char* v) { char *cl=""; switch (c) { case 1: cl="BEGIN"; break; case 2: cl="END"; break; case 3: cl="IF"; break; case 4: cl="THEN"; break; case 5: cl="ELSE"; break; case 6: cl="ID"; break; case 7: cl="INT"; break; case 8: cl="LT"; break; case 9: cl="LE"; break; case 10: cl="EQ"; break; case 11: cl="NE"; break; case 12: cl="GT"; break; case 13: cl="GE"; break; case 14: cl="IS"; break; case 15: cl="PL"; break; case 16: cl="MI"; break; case 17: cl="MU"; break; case 18: cl="DI"; break; case 19: cl="UCON"; break; } printf("(%s,%s)\n",cl,v); } int main(void) { char *fname="file.txt"; FILE *fp; if((fp=fopen(fname,"r"))=NULL) { printf("Error!--Can't open file."); getchar(); exit(1); } else{ scanner_example(fp); } fclose(fp); return 1; }

[Jessica730]

引用 1 楼 棉猴的回复:

把完整代码贴出来吧。另外VC++6.0是我的最爱，没有之一

2楼是我发的完整的源代码

[壹抹尘埃]

应该是文件流那里有问题。 if((fp=fopen(fname,"r"))=NULL) r改成rb试试

[棉猴]

  if((fp=fopen(fname,"r"))=NULL)
  {
     printf("Error!--Can't open file.");
     getchar();
     exit(1);
  }
  else{
      scanner_example(fp);//-----------fp是NULL-------
  }

导致

void scanner_example(FILE *fp)
{
    char ch; 
    int i,c;
    ch=fgetc(fp);//------fp是NULL，所以报错！----------
   .......
}

[棉猴]

if((fp=fopen(fname,"r"))==NULL)//=改成==试试

[Jessica730]

引用 6 楼 棉猴的回复:

if((fp=fopen(fname,"r"))==NULL)//=改成==试试

OK，问题解决了，多谢