| 以下是引用片段： namespace fy_Exp{ namespace {template inline _T GetExpValue(_T t[], char& csym){ char c=csym; csym=0; switch(c){ case '+':return t[0] += t[1]; case '-':return t[0] -= t[1]; case '*':return t[0] *= t[1]; default: return t[0] /= t[1];//case '/': } }} template /* _Tstream: inputstream, _T: get return value * Return nonzero if get value sUCcessfully */ int GetExpValue(_Tstream& istrin, _T& nReturn){ _T t[3] = {0}; //雨中飛燕之作 char csym[3] = "++"; int nLevel = 1, nERR = 0; if(!(istrin>>t[1]))istrin.clear(); for(;;){ if(istrin>>csym[2]){ switch(csym[2]){ case '(': if(!csym[1]){nLevel=0x100; nERR=1;}else if(!GetExpValue(istrin, t[2]))nLevel=0x10; else{nLevel=0x100; nERR=1;} break; case ')': {nLevel = 0x100;}break; case '+':case '-':case '*':case '/': {csym[nLevel++] = csym[2];}break; case ' ':case '/r':case '/n':case '/t':continue; default: {nLevel=0x100; nERR=1;} } if(nLevel==0x100)break; if(nLevel&0x10 istrin>>t[2]){ nLevel &= 0xF; if(nLevel==1){t[1]=t[2];csym[1]=0;continue;} if(csym[1]=='*'csym[1]=='/'){ GetExpValue(t+1, csym[1]); } else{ GetExpValue(t, csym[0]); t[1]=t[2];csym[0]=csym[1];csym[1]=0; } nLevel = 1; } else istrin.clear(); } else{nERR = -1; break;} } if(csym[1])t[2]=0,nReturn=GetExpValue(t+1, csym[1]); else nReturn=GetExpValue(t, csym[0]); return nERR==-1?1:0; }} |
| 以下是引用片段： 程序代碼: #include #include #include using namespace std; int main(void) { string s1; while(cin>>s1) { istrstream isin(s1.data()); double d; if(fy_Exp::GetExpValue(isin, d)) { cout< } else { cout<<"ERROR"< } } return 0; } |
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