Reputation: 85

if else along with >= (2 times) compiles well but doesnt work

I'm making a Grade log application and I have this piece of code here which doesn't work as I intend it to work. (It compiles great with no errors but doesn't work) (please keep in my mind I am a begginer in C++, thank you for your time and knowledge to help me learn also). (The testscore is being given from a series of questions where the value gets a +1 if its correct and a -1 if its wrong.

I think the error is in the => it gets conflicted one with the other but i dont know how to give a value for ex. if the score is < 20 cout = failed if its <40 failedgood but see 20 is < 40 so one overrides the other how could i put if its from 20-40 cout = failed good and if its from 0 - 20 cout = failed. I hope you understand what I mean.

   int testscore;
    string studentmark;

            if ( testscore  == 10 )

            {
                studentmark == ( "failed" );
            }
            else if ( testscore >= 11 && testscore <= 20 )
            {
                studentmark == ( "closebutfailed" );
            }
            else if ( testscore >= 21 && testscore <= 30)
            {
                studentmark == ( "passed" );
                }
            else if ( testscore >= 31 && testscore <= 40 )
            {
                studentmark == ("excelent");
            }
            else if ( testscore >=49 )
            {
                studentmark == ("hasteachersbook");
            }
cout << "Studentmark is:" << studentmark << endl;

Upvotes: 2

Answers (8)

Martin James

Reputation: 24897

Software development is 1% inspiration and 99% debugging. If you cannot debug, you cannot write software.

One often-used debugging technique - KISS:

Comment out or remove as much gunge as possible in an attempt to make a program actually do something. When you get down to:

int testscore;
string studentmark;
        {
            studentmark == ( "failed" );
        }
cout << "Studentmark is:" << studentmark << endl;

..and still you're getting no studentmark output, it will surely dawn that your attempted assignment is not working and therefore almost certainly wrong, (as already explained by other posters, '==' != '=').

Practice/develop your debugging skills before posting here - you will be better off in the long run than just passing your trivial-but-non-working code to a load of experienced developers on a group and getting them to fix your bugs.

Upvotes: 0

Ayush

Reputation: 42450

You need to assign value to studentmark like this:

studentmark = "hasteachersbook";

== checks if the value is equal. = assigns a value.

This should work. If not, the problem is elsewhere.

int testscore;
string studentmark;

if ( testscore  == 10 )
{
    studentmark = "failed";
}
else if ( testscore >= 11 && testscore <= 20 )
{
    studentmark = "closebutfailed";
}
else if ( testscore >= 21 && testscore <= 30)
{
    studentmark = "passed";
    }
else if ( testscore >= 31 && testscore <= 40 )
{
    studentmark = "excelent";
}
else if ( testscore >=41 )
{
    studentmark = "hasteachersbook";
}
else
{
    studentmark = "scoreLessThanTen";
}

Upvotes: 2

Eli Courtwright

Reputation: 193131

First off, your problem is that you should use a single equals sign for assignment, e.g.

studentmark   = "failed";
///         ^^^^ Note single =

Second, you're probably better off writing these if statements as

if (testscore <= 10) { ... }
else if (testscore <= 20) { ... }
else if (testscore <= 30) { ... }
...

Because that's easier to read, and the presence of the else statement means you don't have to test that testscore is greater than the amounts you've already covered.

Upvotes: 14

Matt Fenwick

Reputation: 49105

Your question seems to be "what if my value would be true for more than one of the tests in the if-else chain?"

C++ evaluates in textual order, i.e. from top-to-bottom. Thus, the first predicate that is true for a given value, will be the branch selected.

For example:

int a = 2;

if (a > 0) {
  cout << "First branch";
} else if (a > 1) {
  cout << "Second branch";
}

Even though both tests would be true for a = 2, the first one is selected because it comes first. Thus, First branch is printed out.

Upvotes: 1

Billy ONeal

Reputation: 106609

studentmark == ( "closebutfailed" ); does not assign the value "closebutfailed" into studentmark -- it does an equality comparison between "closebutfailed" and studentmark, which presumably returns false.

Change those to be assignment rather than comparison and try again.

Upvotes: 1