CODEWITHSUNDEEP
c++
Daniel
Daniel

Reputation: 21

Comparing a string with a character in C++

Hey Guys, I'm trying to write a program that calculates the GPA of a student. For some reason the compiler is giving me an error when comparing two strings, but I cant seem to find the reasons for it. Below you will find the piece of code that is giving me error. I would really appreciate if someone could help me figure it out.

ERROR: cannot convert ‘std::string’ to ‘const char*’ for argument ‘1’ to ‘int strncmp(const char*, const char*, size_t)’

double StudentInfo::getGPA() {
double temp = 0;
for(int i = 0; i < totalCourses; i++) { 
    if(strncmp(Courses[i].getGrade(), "A") == 0) //Gets string "grade", and compares it to "A".
        temp = temp + 4;
    if(strncmp(Courses[i].getGrade(),"A-", 2) == 0)
        temp = temp + 3.7;
    if(strncmp(Courses[i].getGrade(), "B+", 2) == 0)
        temp = temp + 3.3;
    if(strncmp(Courses[i].getGrade(), "B") == 0)
        temp = temp + 3;
    if(strncmp(Courses[i].getGrade(), "B-", 2) == 0)
        temp = temp + 2.7;
    if(strncmp(Courses[i].getGrade(), "C+", 2) == 0)
        temp = temp + 2.3;
    if(strncmp(Courses[i].getGrade(), "C") == 0)
        temp = temp + 2;
    if(strncmp(Courses[i].getGrade(), "C-") == 0)
        temp = temp + 1.7;
    if(strncmp(Courses[i].getGrade(), "D+") == 0)
        temp = temp + 1.3;
    if(strncmp(Courses[i].getGrade(), "D") == 0)
        temp = temp + 1;
    else
        temp = temp + 0;
}
GPA = temp/totalCourses;
return GPA;}

Upvotes: 2

Views: 346

Answers (5)

ruslik
ruslik

Reputation: 14870

I would just rewrite your getGrage() function to be 

 float getGrade(){ 
     float grade = 1 + 'D' - toupper(grade[0]); 
     if (grade < 1 || grade > 4) 
         return 0;
     if (grade[1] == '+') return grade + 0.3;
     if (grade[1] == '-') return grade - 0.3;
     return grade;
 };

Upvotes: 0

wkl
wkl

Reputation: 79893

You do not have to use strncmp for this. If you want string equality you can write code like this:

if (Courses[i].getGrade() == "A")
 // ...

edit Note that this works for std::string because it has an overloaded operator==

Upvotes: 9

user387049
user387049

Reputation: 6857

I would try:

if(strncmp(Courses[i].getGrade().c_str(), "A") == 0)

Upvotes: 1

Mihran Hovsepyan
Mihran Hovsepyan

Reputation: 11088

use Courses[i].getGrade().c_str()this returns char* (const char*) of string buffer.

Upvotes: 1

Sanja Melnichuk
Sanja Melnichuk

Reputation: 3505

getGrade() return string then you need Courses[i].getGrade().c_str()

Upvotes: 2

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