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Sep 16th, 2009

Use of pointers to assign values to a string array

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Two lines in the codes below have been remarked out else compiling would fail:

//arrcon[1]=*scon;
//count << "arrcon[1] " << arrcon[1];

The intention was to assign character values to an array with 5 elements, each with a maximum 35 characters, declared as a string array, arrcon[5],[35];

I was trying to use pointer, but there must be bug/s somewhere. It did not work. See codes below.

Kindly point out where I went wrong.

C++ Syntax (Toggle Plain Text)
// pointers     Use of pointers to assign values to a string array
#include <iostream>
#include <stdio.h>
#include <conio.h>
#include <string>
#include <stdlib.h>
 
using namespace std;
int main ()
{
string arrcon[5][35];
string* scon;
string name;
string xcon;
name="YBY";
scon=&name;
xcon=*scon;
 
cout << "\nname =                  " << name;
cout << "\nscon= mem add. of name: " << scon;
cout << "\nxcon= value of name:    " << xcon << "\n\n";
 
// Now using array
 
//arrcon[1]=*scon;
//count << "arrcon[1] " << arrcon[1];
 
// use of pointers courtesy of http://www.cplusplus.com/doc/tutorial/pointers/
cout  << "\n\nUse of pointers courtesy of http://www.cplusplus.com\n\n";
int numbers[5];
int * p;
p = numbers; *p = 10;
p++; *p = 20;
p = &numbers[2]; *p = 30;
p = numbers + 3; *p = 40;
p = numbers; *(p+4) = 50;
 
for (int n=0; n<5; n++) {
    cout << "\t" << numbers[n] << ", ";
    }
 
cout << "\n\n";
getch();
return 0;
}
// pointers     Use of pointers to assign values to a string array
#include <iostream>
#include <stdio.h>
#include <conio.h>
#include <string>
#include <stdlib.h>

using namespace std;
int main ()
{
string arrcon[5][35];
string* scon;
string name;
string xcon;
name="YBY";
scon=&name;
xcon=*scon;

cout << "\nname =                  " << name;
cout << "\nscon= mem add. of name: " << scon;
cout << "\nxcon= value of name:    " << xcon << "\n\n";

// Now using array

//arrcon[1]=*scon;
//count << "arrcon[1] " << arrcon[1];

// use of pointers courtesy of http://www.cplusplus.com/doc/tutorial/pointers/
cout  << "\n\nUse of pointers courtesy of http://www.cplusplus.com\n\n";
int numbers[5];
int * p;
p = numbers; *p = 10;
p++; *p = 20;
p = &numbers[2]; *p = 30;
p = numbers + 3; *p = 40;
p = numbers; *(p+4) = 50;

for (int n=0; n<5; n++) {
    cout << "\t" << numbers[n] << ", ";
    }

cout << "\n\n";
getch();
return 0;
}

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yonghc

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Sep 16th, 2009

Re: Use of pointers to assign values to a string array

This:
string arrcon[5][35];
is basically a table of words/strings composed of 5 lines and 35 words/strings per line. The size of each word/string is indefinite. arrcon[1] is the second line of 35 words/strings, not a single word/string or a pointer to a string. scon is a pointer to a single string/word. *scon is the word/string that scon is pointing to.

Lerner

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Sep 16th, 2009

Re: Use of pointers to assign values to a string array

It is not that you are creating 5 strings of size 35, But actually Creating an 2-d array of 5 rows and 35 columns.

The size of the string is not constant and can extend as much as possible ,until you have the "space" to store such a long string.

Sky Diploma

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Sep 16th, 2009

Re: Use of pointers to assign values to a string array

Click to Expand / Collapse Quote originally posted by Lerner ...

This:
string arrcon[5][35];
is basically a table of words/strings composed of 5 lines and 35 words/strings per line. The size of each word/string is indefinite. arrcon[1] is the second line of 35 words/strings, not a single word/string or a pointer to a string. scon is a pointer to a single string/word. *scon is the word/string that scon is pointing to.

Dear Lerner,

My understanding of arrays is based on basic and foxpro, where you can assign values to arrays. Are there other C++ string functions which can be used for this purpose? Or is c-string array better for this purpose?

yonghc

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Sep 16th, 2009

Re: Use of pointers to assign values to a string array

Click to Expand / Collapse Quote originally posted by Sky Diploma ...

It is not that you are creating 5 strings of size 35, But actually Creating an 2-d array of 5 rows and 35 columns.

The size of the string is not constant and can extend as much as possible ,until you have the "space" to store such a long string.

I was trying to store character values inside an arrays, eg. arrcon[], which can be displayed using a for() loop.
say name="John", weight="56", store these variable values into arrcon[1], arrcon[2]. What are the C++ syntax statements to perform this assignment?

yonghc

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Sep 16th, 2009

Re: Use of pointers to assign values to a string array

I'm not 100% sure what you are asking is this correct?

C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <string>
 
using namespace std;
 
int main()
{
 
	string arrcon[2];
 
	arrcon[0] = "John";
	arrcon[1] = "56";
 
	for( int i = 0; i < 2; i++ )
	{
		cout << arrcon[i] << endl;
	}
 
	system("PAUSE");
	return 0;
}
#include <iostream>
#include <string>

using namespace std;

int main()
{

	string arrcon[2];
	
	arrcon[0] = "John";
	arrcon[1] = "56";
	
	for( int i = 0; i < 2; i++ )
	{
		cout << arrcon[i] << endl;
	}
	
	system("PAUSE");
	return 0;
}

sfuo

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Sep 16th, 2009

Re: Use of pointers to assign values to a string array

You misspelt cout,

(Toggle Plain Text)

  //arrcon[1]=*scon;
 //count << "arrcon[1] " << arrcon[1];

string arrcon[5][35]; is a two-dimensional string array,

C++ Syntax (Toggle Plain Text)
  arrcon[0][0]="Hello";
  arrcon[0][1]=*scon;
  cout << "\n" << arrcon[0][0] << " " << arrcon[0][1];
  arrcon[0][0]="Hello";
  arrcon[0][1]=*scon;
  cout << "\n" << arrcon[0][0] << " " << arrcon[0][1];

adatapost

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Sep 18th, 2009

Re: Use of pointers to assign values to a string array

Click to Expand / Collapse Quote originally posted by adatapost ...

You misspelt cout,
[code]
string arrcon[5][35]; is a two-dimensional string array,
[code]

Dear Adatapost,

Thanks for your tips. i think i got. You need not specify length of each string array element. string arrcon[5][35] is a 2d string array of indefinite length.

The working code snippet below is supported by Borland, CODE::BLOCK and Dev-C++, for the latter two, #include<string> may be removed.

C++ Syntax (Toggle Plain Text)
// pointers3     YBM  Use of pointers to assign values to a string array
#include <iostream>
#include <conio.h>
#include <string>
using namespace std;
int main () {
  string arrcon[5][35];
  string* scon;
  arrcon[0][0]="Hello";
  scon = &arrcon[0][0];
  arrcon[0][1]=*scon;
  cout << "\n" << arrcon[0][0] << " via pointer= " << arrcon[0][1];
  cout << "\n\n";
  getch();
  return 0;
}
// pointers3     YBM  Use of pointers to assign values to a string array
#include <iostream>
#include <conio.h>
#include <string>
using namespace std;
int main () {
  string arrcon[5][35];
  string* scon;
  arrcon[0][0]="Hello";
  scon = &arrcon[0][0];
  arrcon[0][1]=*scon;
  cout << "\n" << arrcon[0][0] << " via pointer= " << arrcon[0][1];
  cout << "\n\n";
  getch();
  return 0;
}

yonghc

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