不好意思，问一个菜鸟问题，关于c++

paulm308

请问乘号除号在c++中有先后顺序吗？谢谢

forest077

有啊。
相同优先级从左到右呗。

yyt98032

呵呵

owencan

原帖由 "forest077" 发表：
有啊。
相同优先级从左到右呗。

就是

lonemoon

这和加减是一样的，看来楼主要看看关于基础知识的书，几乎每本书上都有介绍优先级的！

paulm308

这个其实我也知道，不过有一个程序，要找错误，有一个错误就在*/上面，有点糊涂了，我贴上来大家帮我看看吧。
#include <iostream>;
using namespace std;

// function prototypes
float combinedMark( float labs, float midterm, float assignment, float final );
float adjustMark( float rawTotal, float final, char failFinalFailCourse );


// main() - get input marks, and find out whether or not the instructor
// decides to enforce the "need to pass the final exam to pass the course"
// rule. Then compute (and print) the final grade. If a student fails the
// final exam, but his/her combined average is 50% or more, then a mark of
// 49% will be printed.

int main( void )
{   
    char  failFinalFailCourse;
    float labs;
    float midterm;
    float assignment;
    float final;
    float total;
    float finalGrade;
        int   integerGrade;

    // read the various marks from the keyboard

    cout << "Enter your total lab mark (/ 200): ";
    cin  >;>; labs;

    cout << "Enter your midterm mark (/ 90): ";
    cin  >;>; midterm;

    cout << "Enter your assignment mark (/ 60): ";
    cin  >;>; assignment;

    cout << "Enter your final exam mark (/ 120): ";
    cin  >;>; final;

    // ask if the "fail final, fail course" rule is in effect

    cout << "Will you fail the course if you failed the final exam?\n";
    cout << "Enter Y or N: ";
    cin  >;>; failFinalFailCourse;

    // compute the combined mark and the final mark
    total = combinedMark( labs, midterm, assignment, final );
    finalGrade = adjustMark( total, final, failFinalFailCourse );

    // display the final mark as an integer
        integerGrade = finalGrade + 0.5;  // round off
    cout << "Your final grade for the course is "
                 << integerGrade << "%.\n";

    return 0;
}



// combinedMark - function to combine the labs marks (out of 200), midterm
// marks (out of 90), assignments (out of 60), and final exam mark (out of 120)
// to obtain a final mark for the course. The weight of each is:
//                labs:            15%
//                midterm:    25%
//      assignment: 15%
//      final:      45%

float combinedMark( float labs, float midterm, float assignment, float final )
{
        // Pre:   labs, midterm, and final are all >;= 0
        // Post:  return the tentative final mark for the course

    float scaledLabs;
    float scaledMidterm;
    float scaledAssignment;
    float scaledFinal;
    float combined;

    scaledLabs = labs * 15 / 200;
    scaledMidterm = 25 / 90 * midterm;
    scaledAssignment = assignment * 15 / 60;
    combined = scaledLabs + scaledMidterm + scaledAssignment * scaledFinal;
    return combined;
}



// Adjust marks so that if one fails the final exam and the "fail the
// final, fail the course" rule is in effect, then a final grade of 49%
// is assigned.

float adjustMark( float rawTotal, float final, char failFinalFailCourse )
{
        // Pre:  rawTotal and final are >;= 0, and
        //       failFinalFailCourse is either 'Y' or 'N'
        // Post: return the student's assigned course grade

    if( failFinalFailCourse = 'Y'  &&  final < 60  ||  rawTotal >;= 50 )
        return 49;

    return rawTotal;
}

里边有5个错误，有一个是25/90*midterm的，如果按照这个，每次计算midterm都是0。

lenovo

哪个错误在*/上面，你说说看？
程序我没仔细看。
我看都是float类型，是不是计算精度的问题呀？

paulm308

我自己找到答案了，可能是因为25/60，电脑认为它是integer,所以25/60=0。如果是25.0/60.0就行了。各位看看我说的有道理吗？

lylzp

[quote]原帖由 "paulm308"]我自己找到答案了，可能是因为25/60，电脑认为它是integer,所以25/60=0。如果是25.0/60.0就行了。各位看看我说的有道理吗？[/quote 发表：

是的，int/int=int。
如果两个int型相乘除的时候要先转换，如：
int i,j;
float f;
i = 5;
j = 6;
f = (float)i/(float)j;