Erase part of the string

[flex567]

// string::erase
#include <iostream>
#include <string>

int main ()
{
  std::string str ("This is an example sentence.");
  std::cout << str << '\n';
                                           
  str.erase (10,8);                       
  std::cout << str << '\n';

Output:
This is an sentence.

I don't understand this program. What do these 2 numbers represent? The index of an element in a character array? The 10th character of the array is 'n' and 8th is a "space".

[2kaud]

The first number is the index value into the string for the first char to be erased - which starts at 0 not 1! The second is the number of chars to be erased from this position. See http://www.cplusplus.com/reference/string/string/erase/

[flex567]

oh, i see.

what about this

    string s1 = "***carr***";
    string s2;

    s2 = s1.insert(s1.end(),3,'.');

Why is this not the way to add 3 dots to the end of the string??

[2kaud]

s1.insert(s1.end(),3,'.');

This will indeed add 3 dots to the end of the string s1. But .insert doesn't return an object that can be assigned to a type string. See See http://www.cplusplus.com/reference/s...string/insert/

[flex567]

This will not add 3 dots and .insert returns a string object. I tested it.

[2kaud]

Under VS2013

int main()
{
string s1 = "***carr***";

	cout << s1 << endl;

	s1.insert(s1.end(), 3, '.');

	 cout << s1 << endl;

	 return 0;
}

produces the output

***carr***
***carr***...

What compiler are you using?

[flex567]

miniGw

[flex567]

what is the difference between size_t type and an int type?

[2kaud]

This will not add 3 dots and .insert returns a string object. I tested it.

In c++11, when the first argument to .insert is an iterator, then .insert() returns an iterator (except when using an initializer list). This is slightly different in c++98. See http://www.cplusplus.com/reference/s...string/insert/ for further details.

[2kaud]

what is the difference between size_t type and an int type?

See http://stackoverflow.com/questions/1...-int-vs-size-t

[flex567]

Why this program won't compile?

#include <iostream>
#include <string>
using namespace std;


bool isPalindrom(string s){
    string temp;
    int j = s.size()-1;

    for(int i = 0; i < s.size();i++){

        temp[i] = s[j];
        j--;

    }
    cout << temp << endl;

    return true;

}


int main{

string s1("ana")
isPalindrom(s1);
return 0;}

[flex567]

This one will compile but will produce strange results?

#include <iostream>
#include <string>

using namespace std;

int main{
    
    string s3 = "Ana";
    string ss;
   

    ss.insert(0,s3[0],1);

return 0;}

[2kaud]

As you are not referencing the stl classes by their namespace, you need

using namespace std;

after the includes - or use

std::string ss;

etc

You can't have nested functions. main hasn't been given a parameter list. This will compile

#include <iostream>
#include <string>
using namespace std;

bool isPalindrom(string s){
		string temp;
		int j = s.size() - 1;

		for (int i = 0; i < s.size(); i++){

			temp[i] = s[j];
			j--;

		}
		cout << temp << endl;

		return true;

	}

int main()
{
	isPalindrom("qweewq");

	return 0;
}

[flex567]

I edited both programs and still don't work.

[2kaud]

This one will compile but will produce strange results?

I think you mean

	ss.insert(0, 1, s3[0]);

1st param is position, 2nd is number to insert and 3rd is character to insert. See http://www.cplusplus.com/reference/s...string/insert/