Thread: std::string problem

Hello,

I have a problem with an std::string that is a member of a class.

It is simply declared in the public section of my class like this: "string s;". The class is does not have a cpp file because it only has a bunch of data members. When I try to use it somewhere else like: "cout << myclassinstance->s;" my program crashes. myclassinstance is not null, and I am able to use other members of it of type bool.

What could be the problem?

Was searching for the problem for hours, and then minutes after I posted I found the problem. Sorry about that.


The problem was that I had a subclass pointer pointing to a base class instance. I was able to use the members of the baseclass, but not those of the subclass.

Originally Posted by C+/-

The problem was that I had a subclass pointer pointing to a base class instance. I was able to use the members of the baseclass, but not those of the subclass.

And you achieved that with what sort of cast?

Originally Posted by C+/-

Was searching for the problem for hours, and then minutes after I posted I found the problem. Sorry about that.

Yeah, that happens to me all the time. As soon as you ask someone to look at your code, you find the problem yourself.

Originally Posted by cpjust

Yeah, that happens to me all the time. As soon as you ask someone to look at your code, you find the problem yourself.

That's why I like to recommend what laserlight did. It often lead the person to the solution.

Originally Posted by medievalelks

That's why I like to recommend what laserlight did. It often lead the person to the solution.

Try explaining your problem to the nearest wall. I usually end up solving it in the process of putting it into words.

Originally Posted by brewbuck

Try explaining your problem to the nearest wall. I usually end up solving it in the process of putting it into words.

LOL. I can't count the number of times I was *convinced* there was a compiler bug, only to sheepishly discover that the problem, as always, was in my code.

Code:

explain in details


#include<iostream.h>
#include <math.h>
#include<process.h>
#include<conio.h>
// prototype for the the functions
void getVect(int &s, int &e );
void addition();
void subtraction();
void multiplication();
void length();
int main() // function main begins program execution
{
// let the user know about the program
clrscr();
cout << "\n\n\t program that describes something about vectors.";
char choice;
do{
cout << "\n\n \t\t\t 'M E N U' ";
cout << "\n\n\t\tAddition : A";
cout << "\n\t\tSubtraction : S";
cout << "\n\t\tMultiplication : M";
cout << "\n\t\tLength : L";
cout << "\n\t\tQuit : Q";
cout << "\n\n\t\tEnter your choice ";
cin >> choice;
//ff convert the choice to lower case
if ( choice < 97)
choice +=32;
switch ( choice )
{
case 'a' : addition();
break;
case 's' : subtraction();
break;
case 'm' : multiplication();
break;
case 'l' : length();
break;
case 'q' : //ff pause the screen
cout << "\n\n\t";
exit(0);
break;
default : cout << "\n\n\tYou have entered wrong choice";
} //ff end switch
} while (choice !='q'); // end do-while
return 0; //ff indicate program executed successfully
} //ff end of function, main

void getVect( int &f, int &s )
{
//fix" prompt and read the values into the vector
cout << "\n\tEnter the values for the vector:";
cout << "\n\tFirst Component : ";
cin >> f;
cout << "\tSecond Component : ";
cin >>s;
cout << "'\tThe vector is [ " << f << " , " << s << " ]";;
} // end function getVect

void addition()
{
//ff declare the variables
int a1, a2, b1, b2 ;
//ff get the values for the first vector
getVect( a1, a2 );
//ff get the values for the second vector
getVect( b1, b2 );
//ff do the addition
cout<< "\n\n\tThe sum is [ " << ( a1 + b1 )<< "," << ( a2 + b2 ) << "]" ;
} //ff end function addition

void subtraction()
{
// declare the variables
int al, a2, bl, b2 ;
//ff get the values for the first vector
getVect( al, a2 );
//ff get the values for the second vector
getVect( bl, b2 );
//ff do the subtraction
cout << "\n\n\t‘I‘he difference is [ " << ( al - bl )<<", "<<(a2-b2)<<"]";
} //fs'] end function subtraction



void multiplication()
{
//fix" declare the variables
int al, a2, bl, b2 ;
//fra" get the values for the first vector
getVect(al, a2) ;
//fra" get the values for the second vector
getVect( bl, b2 );
//ff do the multiplication
cout << "\n\n\tThe product is [ "  << ( al * bl )<< ", " << (a2 * b2) <<"]";
}// ff end function multiplication
void length()
{
//ff declare the variables
int a1, a2;
float len;

//ff get the values for the vector
getVect(a1,a2);
//fir'] find the length
a1=a1*a1;
a2=a2*a2;
len=a1+a2;
len=sqrt(len);
cout << "\n\n\tlength is "<<len;

}
// end function length 
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 Yesterday, 07:07 PM    #9  
basharat 
Registered User
 

Join Date: May 2008
Posts: 4  Code:
#include<iostream.h>
#include <math.h>
#include<process.h>
#include<conio.h>
// prototype for the the functions
void getVect(int &s, int &e );
void addition();
void subtraction();
void multiplication();
void length();
int main() // function main begins program execution
{
// let the user know about the program
clrscr();
cout << "\n\n\t program that describes something about vectors.";
char choice;
do{
cout << "\n\n \t\t\t 'M E N U' ";
cout << "\n\n\t\tAddition : A";
cout << "\n\t\tSubtraction : S";
cout << "\n\t\tMultiplication : M";
cout << "\n\t\tLength : L";
cout << "\n\t\tQuit : Q";
cout << "\n\n\t\tEnter your choice ";
cin >> choice;
//ff convert the choice to lower case
if ( choice < 97)
choice +=32;
switch ( choice )
{
case 'a' : addition();
break;
case 's' : subtraction();
break;
case 'm' : multiplication();
break;
case 'l' : length();
break;
case 'q' : //ff pause the screen
cout << "\n\n\t";
exit(0);
break;
default : cout << "\n\n\tYou have entered wrong choice";
} //ff end switch
} while (choice !='q'); // end do-while
return 0; //ff indicate program executed successfully
} //ff end of function, main

void getVect( int &f, int &s )
{
//fix" prompt and read the values into the vector
cout << "\n\tEnter the values for the vector:";
cout << "\n\tFirst Component : ";
cin >> f;
cout << "\tSecond Component : ";
cin >>s;
cout << "'\tThe vector is [ " << f << " , " << s << " ]";;
} // end function getVect

void addition()
{
//ff declare the variables
int a1, a2, b1, b2 ;
//ff get the values for the first vector
getVect( a1, a2 );
//ff get the values for the second vector
getVect( b1, b2 );
//ff do the addition
cout<< "\n\n\tThe sum is [ " << ( a1 + b1 )<< "," << ( a2 + b2 ) << "]" ;
} //ff end function addition

void subtraction()
{
// declare the variables
int al, a2, bl, b2 ;
//ff get the values for the first vector
getVect( al, a2 );
//ff get the values for the second vector
getVect( bl, b2 );
//ff do the subtraction
cout << "\n\n\t‘I‘he difference is [ " << ( al - bl )<<", "<<(a2-b2)<<"]";
} //fs'] end function subtraction



void multiplication()
{
//fix" declare the variables
int al, a2, bl, b2 ;
//fra" get the values for the first vector
getVect(al, a2) ;
//fra" get the values for the second vector
getVect( bl, b2 );
//ff do the multiplication
cout << "\n\n\tThe product is [ "  << ( al * bl )<< ", " << (a2 * b2) <<"]";
}// ff end function multiplication
void length()
{
//ff declare the variables
int a1, a2;
float len;

//ff get the values for the vector
getVect(a1,a2);
//fir'] find the length
a1=a1*a1;
a2=a2*a2;
len=a1+a2;
len=sqrt(len);
cout << "\n\n\tlength is "<<len;

}// end function length 

Explain  each and every statement and what functions  insted of the functions are used and what other codes are used inted of that used in the program
clerify the steps

Code:

 i dont brake Your privicy i am a student i write the codes and want details about each and every step and each and every code and each and every function and each and every type of function please explain the codes in details

Originally Posted by basharat

i dont brake Your privicy i am a student i write the codes and want details about each and every step and each and every code and each and every function and each and every type of function please explain the codes in details

Originally Posted by Elysia

Indent.
Don't use code tags for comments.
And don't expect anyone to muffle through all of that code and tell you exactly what happens.
Post a smaller sample.

Yeah, and while you're at it, don't hijack other peoples threads...
Read a C++ book. If you still have questions, post your own question in a new thread.