Programming Forums > Application Development > C++

brad sue · Sep 23rd, 2006, 9:40 PM

Hi ,
I am coding a 'test corrector' machine.

I need to read a name from a file .
The student name is delimitated by the '#' sign . After the name is a space and then the response to the test in form of T (true)and F(false).

I want to read the name of the student, followed by his answer, followed by the test score.

Each correct answer counts 2 points, each wrong answer -1 point, and no answer 0 point.

My problem is that my score is not right.

for example, the file is like this:
TFFTFFTTTTFFTFTFTFTF // test key
John Doe# TFTFTFTT TFTFTFFTTFT // note the blank in the response!

my output should be:
John Doe TFTFTFTT TFTFTFFTTFT score=8 (I think ! but I found 22!!)

I don't know why my score is wrong. Here is my code:

(Toggle Plain Text)

#include<fstream>
#include <iostream>
#include <cstdlib>

using namespace std;
const int SIZE=100;

int main()
{
    ifstream fin;
    ofstream fout;
    
    fin.open("input.txt");
    if(fin.fail())
    {
        cerr<<" Input file opening failed.\n";
        exit(1);
    }          


    fout.open("out1.txt");
    if(fout.fail())
    {
        cerr<<" output file opening failed.\n";
        exit(1);
    }    
    
    char name[SIZE]={0};     
    char key[20];// key of the test
    char test[20];// response of student
    char next;// char used to adjust see below
    
    // read key
    for(int i=0;i<20;i++)
    {
       fin>>key[i];
    }  
    // display   key
    for(int i=0;i<20;i++)
    {
       cout<<key[i];
    } 
    cout<<endl;    
    
    int index=0;
    int point=0;
    static int score=0; 
         
    while( fin)
    {
        fin.get(name,SIZE,'#');
        cout << name << endl;
        point=strlen(name);// check to kow where the file cursor is!
       
       
        fin.get(next);// adjust beginning student response array
        fin.get(next);
        
        fin.get(test,100,'\n');
        cout<<test;
        
        for(int i=0;i<20;i++)// score calculation
              {  
                  if(key[i]==test[i]) 
                      { score=score+2; }
                  
                  if(test[i]!=' ')  
                      { score=score+0;}
                      
                  else {score=score-1;}    
         
              }// end for

              cout<<" "<<score;
          
    }
    
    fin.close();
    fout.close();
    
    return 0;
}

please can someone help me .
I first had some difficulty to read the name and then the response, and I dont know if I 've done it correctly

Thank you
B

DaWei · Sep 23rd, 2006, 10:09 PM

What is this?

(Toggle Plain Text)

                  if(test[i]!=' ')  
                      { score=score+0;}

If you don't do anything to the score, it's the same as adding zero. I would write it like this:

(Toggle Plain Text)

if (test [i]  != ' ')
{
   // There's an answer
   if (test [i] == key [i]) score += 2;
   else score -= 1;
}

Secondly, it would be better to use the string class. I would read the entire line and pluck the two parts out as substrings.

brad sue · Sep 24th, 2006, 10:00 AM

Quote:

Originally Posted by DaWei

What is this?

(Toggle Plain Text)

                  if(test[i]!=' ')  
                      { score=score+0;}

If you don't do anything to the score, it's the same as adding zero. I would write it like this:

(Toggle Plain Text)

if (test [i]  != ' ')
{
   // There's an answer
   if (test [i] == key [i]) score += 2;
   else score -= 1;
}

Secondly, it would be better to use the string class. I would read the entire line and pluck the two parts out as substrings.

Thank you Dawei.
beside the silly

(Toggle Plain Text)

score=score+0;

I often mess up what I want to compare to. ( like key [i]==test [i] instead of test [i] == key [i])
I think we are going to look at class string next week. We'll see if I can change it as we go along.

DaWei · Sep 24th, 2006, 10:54 AM

We all do silly stuff, Brad. I haven't done it in a long time, of course. Yesterday, I think. Hang in there.

brad sue · Sep 26th, 2006, 11:01 PM

Quote:

Originally Posted by brad sue

Hi ,
I am coding a 'test corrector' machine.

I need to read a name from a file .
The student name is delimitated by the '#' sign . After the name is a space and then the response to the test in form of T (true)and F(false).

I want to read the name of the student, followed by his answer, followed by the test score.

Each correct answer counts 2 points, each wrong answer -1 point, and no answer 0 point.

My problem is that my score is not right.

for example, the file is like this:
TFFTFFTTTTFFTFTFTFTF // test key
John Doe# TFTFTFTT TFTFTFFTTFT // note the blank in the response!

my output should be:
John Doe TFTFTFTT TFTFTFFTTFT score=8 (I think ! but I found 22!!)

I don't know why my score is wrong. Here is my code:

(Toggle Plain Text)

#include<fstream>
#include <iostream>
#include <cstdlib>

using namespace std;
const int SIZE=100;

int main()
{
    ifstream fin;
    ofstream fout;
    
    fin.open("input.txt");
    if(fin.fail())
    {
        cerr<<" Input file opening failed.\n";
        exit(1);
    }          


    fout.open("out1.txt");
    if(fout.fail())
    {
        cerr<<" output file opening failed.\n";
        exit(1);
    }    
    
    char name[SIZE]={0};     
    char key[20];// key of the test
    char test[20];// response of student
    char next;// char used to adjust see below
    
    // read key
    for(int i=0;i<20;i++)
    {
       fin>>key[i];
    }  
    // display   key
    for(int i=0;i<20;i++)
    {
       cout<<key[i];
    } 
    cout<<endl;    
    
    int index=0;
    int point=0;
    static int score=0; 
         
    while( fin)
    {
        fin.get(name,SIZE,'#');
        cout << name << endl;
        point=strlen(name);// check to kow where the file cursor is!
       
       
        fin.get(next);// adjust beginning student response array
        fin.get(next);
        
        fin.get(test,100,'\n');
        cout<<test;
        
        for(int i=0;i<20;i++)// score calculation
              {  
                  if(key[i]==test[i]) 
                      { score=score+2; }
                      
                  else {score=score-1;}    
         
              }// end for

              cout<<"  score="<<score;
          
    }
    
    fin.close();
    fout.close();
    
    return 0;
}

please can someone help me .
I first had some difficulty to read the name and then the response, and I dont know if I 've done it correctly

Thank you
B

I have something weird with my output.
It is like the program reads one more line and compute a a score .

It is like this:

jose frits TTFTTTFFFTFTTFFTTF score=23
deinse guile FTTTTFTFTTFFFTTFT score=19
--------(this is all blank)----------score=13// this the 'invisible line'

I don't knoe why it is doing this. I checked my program and nothing indicates that it should read one more line and I don't think the end of file is the issue.
please can someone see my problem?

Thank you
B

DaWei · Sep 27th, 2006, 5:40 AM

Sure, EOF is the issue. Your last read grabs the last line and newline. That is not EOF, since you haven't attempted to read beyond it. The "while (fin)" looks fine, so you attempt to read again and hit EOF. You aren't checking for that. This is one of most common novice mistakes.

brad sue · Oct 3rd, 2006, 12:03 AM

Quote:

Originally Posted by DaWei

Sure, EOF is the issue. Your last read grabs the last line and newline. That is not EOF, since you haven't attempted to read beyond it. The "while (fin)" looks fine, so you attempt to read again and hit EOF. You aren't checking for that. This is one of most common novice mistakes.

Dawei, can I have some clarifications about what you are saying because I am not able to see what to modify.
Thank you
B

DaWei · Oct 3rd, 2006, 7:37 AM

Presume that this is the last thing in your file: abcdefg\n(EOF). The input mechanism is satisfied when it reads the \n. It is sitting between that and the EOF. You use that, then return to the top of the while, which is NOT showing EOF. You read and immediately hit EOF. Since you aren't looking to see if that's the case, you read for a name, some chars, and some scores, each of which does absolutely nothing, since the stream failed on the try for a name and has been blithely ignoring you. Didn't keep you from trying to use the stuff you already had, though. Look at each individual read mechanism you use. Ask what happens if it hits EOF before getting anything. If you don't, you'll reuse crap. Ask, also, what happens if it hits EOF AFTER getting some stuff. If you don't recognize THAT, you'll throw good stuff away. It is a common newbie mistake to rely on EOF or FAIL in the while expression, only. Sometimes that's workable, mostly not.

Sep 23rd, 2006, 9:40 PM	#1
brad sue Hobbyist Programmer Join Date: Mar 2006 Posts: 115 Rep Power: 3	test score Hi , I am coding a 'test corrector' machine. I need to read a name from a file . The student name is delimitated by the '#' sign . After the name is a space and then the response to the test in form of T (true)and F(false). I want to read the name of the student, followed by his answer, followed by the test score. Each correct answer counts 2 points, each wrong answer -1 point, and no answer 0 point. My problem is that my score is not right. for example, the file is like this: TFFTFFTTTTFFTFTFTFTF // test key John Doe# TFTFTFTT TFTFTFFTTFT // note the blank in the response! my output should be: John Doe TFTFTFTT TFTFTFFTTFT score=8 (I think ! but I found 22!!) I don't know why my score is wrong. Here is my code: (Toggle Plain Text) #include<fstream> #include <iostream> #include <cstdlib> using namespace std; const int SIZE=100; int main() { ifstream fin; ofstream fout; fin.open("input.txt"); if(fin.fail()) { cerr<<" Input file opening failed.\n"; exit(1); } fout.open("out1.txt"); if(fout.fail()) { cerr<<" output file opening failed.\n"; exit(1); } char name[SIZE]={0}; char key[20];// key of the test char test[20];// response of student char next;// char used to adjust see below // read key for(int i=0;i<20;i++) { fin>>key[i]; } // display key for(int i=0;i<20;i++) { cout<<key[i]; } cout<<endl; int index=0; int point=0; static int score=0; while( fin) { fin.get(name,SIZE,'#'); cout << name << endl; point=strlen(name);// check to kow where the file cursor is! fin.get(next);// adjust beginning student response array fin.get(next); fin.get(test,100,'\n'); cout<<test; for(int i=0;i<20;i++)// score calculation { if(key[i]==test[i]) { score=score+2; } if(test[i]!=' ') { score=score+0;} else {score=score-1;} }// end for cout<<" "<<score; } fin.close(); fout.close(); return 0; } #include<fstream> #include <iostream> #include <cstdlib> using namespace std; const int SIZE=100; int main() { ifstream fin; ofstream fout; fin.open("input.txt"); if(fin.fail()) { cerr<<" Input file opening failed.\n"; exit(1); } fout.open("out1.txt"); if(fout.fail()) { cerr<<" output file opening failed.\n"; exit(1); } char name[SIZE]={0}; char key[20];// key of the test char test[20];// response of student char next;// char used to adjust see below // read key for(int i=0;i<20;i++) { fin>>key[i]; } // display key for(int i=0;i<20;i++) { cout<<key[i]; } cout<<endl; int index=0; int point=0; static int score=0; while( fin) { fin.get(name,SIZE,'#'); cout << name << endl; point=strlen(name);// check to kow where the file cursor is! fin.get(next);// adjust beginning student response array fin.get(next); fin.get(test,100,'\n'); cout<<test; for(int i=0;i<20;i++)// score calculation { if(key[i]==test[i]) { score=score+2; } if(test[i]!=' ') { score=score+0;} else {score=score-1;} }// end for cout<<" "<<score; } fin.close(); fout.close(); return 0; } please can someone help me . I first had some difficulty to read the name and then the response, and I dont know if I 've done it correctly Thank you B

Sep 23rd, 2006, 10:09 PM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	What is this? (Toggle Plain Text) if(test[i]!=' ') { score=score+0;} if(test[i]!=' ') { score=score+0;} If you don't do anything to the score, it's the same as adding zero. I would write it like this: (Toggle Plain Text) if (test [i] != ' ') { // There's an answer if (test [i] == key [i]) score += 2; else score -= 1; } if (test [i] != ' ') { // There's an answer if (test [i] == key [i]) score += 2; else score -= 1; } Secondly, it would be better to use the string class. I would read the entire line and pluck the two parts out as substrings. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Sep 24th, 2006, 10:54 AM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	We all do silly stuff, Brad. I haven't done it in a long time, of course. Yesterday, I think. Hang in there. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Sep 27th, 2006, 5:40 AM	#6
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Sure, EOF is the issue. Your last read grabs the last line and newline. That is not EOF, since you haven't attempted to read beyond it. The "while (fin)" looks fine, so you attempt to read again and hit EOF. You aren't checking for that. This is one of most common novice mistakes. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Oct 3rd, 2006, 7:37 AM	#8
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Presume that this is the last thing in your file: abcdefg\n(EOF). The input mechanism is satisfied when it reads the \n. It is sitting between that and the EOF. You use that, then return to the top of the while, which is NOT showing EOF. You read and immediately hit EOF. Since you aren't looking to see if that's the case, you read for a name, some chars, and some scores, each of which does absolutely nothing, since the stream failed on the try for a name and has been blithely ignoring you. Didn't keep you from trying to use the stuff you already had, though. Look at each individual read mechanism you use. Ask what happens if it hits EOF before getting anything. If you don't, you'll reuse crap. Ask, also, what happens if it hits EOF AFTER getting some stuff. If you don't recognize THAT, you'll throw good stuff away. It is a common newbie mistake to rely on EOF or FAIL in the while expression, only. Sometimes that's workable, mostly not. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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