C++ :

#include <cstdio>
#include <cstdlib>
/* 多组数据，每组一行；读到「单独一行 0」结束（该行不输出）。
   普通优先级：维护「当前项 term」与「累加和 total」。
   '+'/'-' 表示当前项结算并开启新项；'*'/'/' 直接作用在当前项上。
   除法为实数除法。每行 <= 200 字符。 */
static char line[1005];
int main(){
    while(fgets(line, sizeof(line), stdin)){
        char *p = line;
        while(*p == ' ' || *p == '\t') p++;
        if(*p == '0'){
            char *q = p + 1;
            int only = 1;
            while(*q && *q != '\n' && *q != '\r'){
                if(*q != ' ' && *q != '\t'){ only = 0; break; }
                q++;
            }
            if(only) break;
        }
        double total = 0.0, term;
        char *q = p;
        term = strtod(q, &q);
        while(1){
            while(*q == ' ' || *q == '\t') q++;
            if(*q == '\0' || *q == '\n' || *q == '\r') break;
            char c = *q++;
            while(*q == ' ' || *q == '\t') q++;
            double num = strtod(q, &q);
            if(c == '+'){ total += term; term = num; }
            else if(c == '-'){ total += term; term = -num; }
            else if(c == '*'){ term *= num; }
            else if(c == '/'){ term /= num; }
        }
        total += term;
        printf("%.2f\n", total);
    }
    return 0;
}