Char problem

[Ch1156]

Im working on my vector and trying to create a error catcher of sorts. but my char wont work, i dont get it here it is:

#include <iostream>
#include <vector>

using namespace std;

 int main()
 {
     vector<float> student_marks(10);

     for (vector<float>::size_type i = 0; i < 10; i++)
     {
         cout << "Enter marks for student #" << i+1 << ": " << flush;
         cin >> student_marks[i];
     }
 }

void num()
{
    char numbers = {'1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '\0'};
}

I get these errors:

C:\Users\Chay Hawk\Desktop\Vector\main.cpp||In function 'void num()':|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|19|error: scalar object 'numbers' requires one element in initializer|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|19|warning: unused variable 'numbers'|
||=== Build finished: 1 errors, 1 warnings ===|

i put char numbers[9] and it said this:

C:\Users\Chay Hawk\Desktop\Vector\main.cpp||In function 'void num()':|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|19|error: too many initializers for 'char [9]'|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|19|warning: unused variable 'numbers'|
||=== Build finished: 1 errors, 1 warnings ===|
 
I changed it again to [1] and it says the same thing as above.

What am i doing wrong i dont get it, i was reading on chars here on the site but i didnt find a solution.

[Texan40]

`char' is a single character. If you want an array of char you can do:

char numbers[] = {'1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '\0' };

[Disch]

Also, if you're null terminating it like that, you don't need to do the whole {} initialization thing. You can just use quotes:

char numbers[] = "1234567890"; // <- same thing

[Ch1156]

Hmm, i see. Well i have an error, :

||=== Vector, Debug ===|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp||In function 'int main()':|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|18|error: 'numbers' was not declared in this scope|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp||In function 'void num()':|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|25|warning: overflow in implicit constant conversion|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|25|warning: unused variable 'numbers'|
||=== Build finished: 1 errors, 2 warnings ===|


Code:

#include <iostream>
#include <vector>

using namespace std;

void num();

 int main()
 {
     vector<float> student_marks(10);

     for (vector<float>::size_type i = 0; i < 10; i++)
     {
         cout << "Enter marks for student #" << i+1 << ": " << flush;
         cin >> student_marks[i];
     }

     if(student_marks != numbers){
        cout << "Error" << endl;
     }
 }

void num()
{
    char numbers[] = {1234567890};
}

i tried googleing "overflow in implicit constant conversion" but i didnt fina good nderstanding of the problem.

[Texan40]

needs to be :

char numbers[] = "1234567890";

EDIT: The "overflow" is because it is trying to assign the integer value 1234567890 to a character which can only hold a maximum value of 128.

[Ch1156]

Ah, crap i didnt see that, sorry. I still get errors:

C:\Users\Chay Hawk\Desktop\Vector\main.cpp||In function 'int main()':|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|18|error: 'numbers' was not declared in this scope|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp||In function 'void num()':|
C:\Users\Chay Hawk\Desktop\Vector\main.cpp|25|warning: unused variable 'numbers'|
||=== Build finished: 1 errors, 1 warnings ===|

I dont understand this one 'numbers' was not declared in this scope i put void num(); at the top so it should understand what im trying to do? I tried changing it to num() and i tried num.numbers, but nothing. Also you say "a character which can only hold a maximum value of 128." those were only ten characters though? or do the numbers have a high bit value??

#include <iostream>
#include <vector>

using namespace std;

void num();

 int main()
 {
     vector<float> student_marks(10);

     for (vector<float>::size_type i = 0; i < 10; i++)
     {
         cout << "Enter marks for student #" << i+1 << ": " << flush;
         cin >> student_marks[i];
     }

     if(student_marks != numbers){
        cout << "Error" << endl;
     }
 }

void num()
{
    char numbers[] = "1234567890";
}

[Texan40]

Numbers is out of scope in main() because it is both created and destroyed in num(). Instead of having a function you can just put:

#include <iostream>
#include <vector>

using namespace std;

char numbers[] = "1234567890";

 int main()
 {
     vector<float> student_marks(10);

     for (vector<float>::size_type i = 0; i < 10; i++)
     {
         cout << "Enter marks for student #" << i+1 << ": " << flush;
         cin >> student_marks[i];
     }

     if(student_marks != numbers){
        cout << "Error" << endl;
     }
 }

EDIT: By sticking the numbers between braces it told the compiler you wanted to assign that value but a char is only 8-bit so the highest a (signed) char can be is "01111111" which is 127. An unsigned char would take advantage of the last bit so the max would be 255.

char numbers[] = { 1234567890 }; // tries to stick the number 1,234,567,890 into the 8-bit value (which it can't hold thus the overflow)
char numbers[] = "1234567890"; // sticks the ascii value for 1, 2, 3, etc into the array of 8-bit values

[vlad from moscow]

if(student_marks != numbers){
cout << "Error" << endl;
}

This code is invalid because you cannot compare vector of floats with character array.

[Ch1156]

"By sticking the numbers between braces it told the compiler you wanted to assign that value but a char is only 8-bit so the highest a (signed) char can be is "01111111" which is 127. An unsigned char would take advantage of the last bit so the max would be 255.

char numbers[] = { 1234567890 }; // tries to stick the number 1,234,567,890 into the 8-bit value (which it can't hold thus the overflow)
char numbers[] = "1234567890"; // sticks the ascii value for 1, 2, 3, etc into the array of 8-bit values "

Ah i see now.

"This code is invalid because you cannot compare vector of floats with character array."

So how can i check if the user inputs something other than a number and then give an error?

[vlad from moscow]

First of all take into acccount that you are entering float numbers, because your vector has elements of type float. So a do not see any sense to compare float numbers with integer digits. The overloaded operator >> for cin does all needed checks. It does not allow to enter something else than a float number.

Maybe you should to declare a vector of integers?

[Ch1156]

But when i enter a letter it screws up and exits, i want it to catch the error and not do that, i think i understand what you mean, i'll try it and be back!

[Ch1156]

bump ok i tried a few things and they didnt work. I tried making a string that catches the user input that isnt a number but it didnt work. Maybe i did it wrong but idk.