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Why this code doesnt work?

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Join Date: Nov 2009

Posts: 2

Reputation: lucky_43 is an unknown quantity at this point

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lucky_43

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Newbie Poster

Why this code doesnt work?

Nov 7th, 2009

Hello..
Ive written this code which dont work, its jobis simply recieving names from the user in a structure [a] and delete a name that chosen by user, the compiler give me error flag in the line noticed bellow

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream.h>
#include <conio.h>
 
struct m{
       char n[15];       
       };
 
 
 
 
void main()          
{
   m a[50];             
    char name[15];            
     int i,size;
    cin>>size;       
 
 
 
    for(i=0;i<size;i++)
    {
          cout<<"entr elements";
    cin>>(a[i]).n;
 
}
cout<<"enter elment";
    cin>>name;
 
 
    for (int j=0;j<size;j++)
    {
    if((a[j]).n==name)
    for(int c=j; c<size;c++)
    ((a[c]).n)=((a[c+1]).n);            //this is The LINE
}
    for(i=0;i<size;i++)
    cout<<(a[i]).n<<endl;
 
getch();
}
#include <iostream.h>
#include <conio.h>

struct m{
       char n[15];       
       };
       

        

void main()          
{
   m a[50];             
    char name[15];            
     int i,size;
    cin>>size;       
    
   
    
    for(i=0;i<size;i++)
    {
          cout<<"entr elements";
    cin>>(a[i]).n;

}
cout<<"enter elment";
    cin>>name;
    
    
    for (int j=0;j<size;j++)
    {
    if((a[j]).n==name)
    for(int c=j; c<size;c++)
    ((a[c]).n)=((a[c+1]).n);            //this is The LINE
}
    for(i=0;i<size;i++)
    cout<<(a[i]).n<<endl;
    
getch();
}

Last edited by lucky_43; Nov 7th, 2009 at 1:26 pm.

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Join Date: Oct 2005

Posts: 481

Reputation: Clinton Portis is on a distinguished road

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Clinton Portis Clinton Portis is offline

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Posting Pro in Training

Nov 7th, 2009

Since you are using c-strings (character arrays) you do not get the luxury of using the <string> class overloaded == equality test.

But what you do get is a bunch of <cstring> library functions that will allow you to handle your character arrays with great ease:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include<cstring>
 
//instead of this
if((a[j]).n==name)
 
//try this
if(strcmp(a[j].n, name))
#include<cstring>

//instead of this
if((a[j]).n==name)

//try this
if(strcmp(a[j].n, name))

Last edited by Clinton Portis; Nov 7th, 2009 at 1:35 pm.

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Join Date: Nov 2009

Posts: 2

Reputation: lucky_43 is an unknown quantity at this point

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lucky_43

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Newbie Poster

Nov 7th, 2009

•

Originally Posted by Clinton Portis

Since you are using c-strings (character arrays) you do not get the luxury of using the <string> class overloaded == equality test.

But what you do get is a bunch of <cstring> library functions that will allow you to handle your character arrays with great ease:
Help with Code Tags

C++ Syntax (Toggle Plain Text)
#include<cstring>
 
//instead of this
if((a[j]).n==name)
 
//try this
if(strcmp(a[j].n, name))
#include<cstring> //instead of this if((a[j]).n==name) //try this if(strcmp(a[j].n, name))

Thank You Very much

I used your idea
even though it is right but it is not enough
the compiler still giving me An "Lvalue Required" Error

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Join Date: Oct 2009

Posts: 138

Reputation: restrictment is on a distinguished road

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restrictment restrictment is offline

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Junior Poster

Nov 7th, 2009

It simply means that the left value must be a single variable. You cannot have an equation equal to an equation. Try revising it a bit, and see if you can get it to work.

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Join Date: Oct 2005

Posts: 481

Reputation: Clinton Portis is on a distinguished road

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Clinton Portis Clinton Portis is offline

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Posting Pro in Training

Nov 7th, 2009

This is how I would write your block o' code:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include<cstring>
 
for (int j=0;j<size;j++)
{
     if(strcmp(a[j].n, name)
    {
          strcpy(a[j].n, name);
          break;
    }
}
#include<cstring>

for (int j=0;j<size;j++)
{
     if(strcmp(a[j].n, name)
    {
          strcpy(a[j].n, name);
          break;
    }
}

The code I provided you is untested. Please let me know where any additional errors are with line number.

Some rules to remember:

you can use all boolean logic when at the 'char' level (comparing 'chars' to 'chars') you can also assign chars to other chars.

You cannot directly use boolean logic to directly compare c-strings to other c-strings (arrays to arrays)

You can assign an array pointer to an array pointer of the appropriate type (assign an array to an array pointer) if the appropriate amount of memory has been allocated.

Only if you are using <string> class objects can you compare to 'string' type variables using == equality test, or assign one string to another using the = assignment operator, or 'concantinate' (add to) an existing string using the += 'accumulation' operator.

Last edited by Clinton Portis; Nov 7th, 2009 at 2:10 pm.