[c++]Question about setw

[Banfa]

Doesn`t `setw` set the width of the column to which the data is printed?; whereas \t sets the width of the column separating the 2 data columns.
e.g.
cout<<setw(3)<< i<<"\t"<<setw(5 )<<i*i<<"\n"; //might keep the data columns tidier.

\t does not set the width to anything, it is a character and how it is handled normally depends on the terminal to which you send it.

Commonly the terminal moves the output cursor to the next column multiple of 8.

[Banfa]

weaknessforcats am I doing something wrong in my code because I can't find anything about a stringstream only being capable of being used once.

You can reuse a stringstream, however in doing so you need to reset it first before you try to use it call the method

stringstream::c lear();

on your instance of the class before trying to reuse it.

[whodgson]

Doesn`t `setw` set the width of the column to which the data is printed?; whereas \t sets the width of the column separating the 2 data columns.
e.g.
cout<<setw(3)<< i<<"\t"<<setw(5 )<<i*i<<"\n"; //might keep the data columns tidier.

[Simonius]

weaknessforcats am I doing something wrong in my code because I can't find anything about a stringstream only being capable of being used once.

[weaknessforcats]

Yes, that works but only for an int. If a double were entered, you will need to do something else to get the number of characters in the double.

[Banfa]

Have you considered inserting the integer in a stringstream and recovering it as a string?? That way string::size() would be the number of characters in the integer.

That seems like a rather conveluted way to me when a simple for loop dividing by the base you are interested in until you read 0 would achieve the same thing

[code=cpp]
int CountDigits(int number unsigned base)
{
int count;

if (base == 0) // Prevent divide by 0
{
return 0;
}

for(count=1; number; count++)
{
number /= base;
}

return count;
}
[/code]

[Simonius]

Question, can a stringstream only be used once?
Because while the following code seems ok to me, setw2 also equals 3 while it should be 5.
I've run the program partially to before width2=.. to check where the error is and size seems to stay 100 while it should turn 100000.

// exercise 2.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <sstream>
#include <iomanip>

using std::cout;		using std::stringstream;
using std::string;		using std::setw;

int main()
{
	int i=0, max, width1, width2;
	max=100;
	
	{stringstream store;
	store<<max;
	string size;
	store>>size;
	width1=size.length();
	i=max*max;
	store<<i;
	store>>size;
	width2=(size.length());
	}

	for(i=0;i<=max;i++)
		cout<<setw(width1)<<i<<setw(width2)<<i*i<<"\n";
	system("PAUSE");
	return 0;
}

[Ganon11]

Yep. That's what I get for not actually having used the stringstream.

[weaknessforcats]

At first glance it looks to me like it should be
SS << myInt;
SS >> myStr;

Yes it should. Just a typo.

[Simonius]

Hello, sorry for the late response but I've been quite busy.

Which libraries & namespaces do I need for your example?

And I could be mistaken due to not having tested it yet and not having worked with streams yet but didn't you switch the >> and <<?

At first glance it looks to me like it should be
SS << myInt;
SS >> myStr;

[Ganon11]

Well, the reverse of int atoi(char*) is simply char* itoa(int), but these are both legacy C functions that should be avoided in C++. A stringstream will act like a stream (that's cin and cout) that can take your number and spit out a string, or vice versa, like this:

[CODE=cpp]int myInt = 1234;
string myStr;
stringstream SS;
SS >> myInt; // Read a value into the stream
SS << myStr; // Extract a value from the stream
// Now myStr is "1234"[/CODE]

[Simonius]

I know about atoi to convert from a string to a number, but I haven't found anything about the reverse.

[Simonius]

I would insert it into a string if I know how to convert from string to int and from int to string for the first time.
A follow up question is to adapt it to another number.

The book hasn't shown that much yet.

[weaknessforcats]

Have you considered inserting the integer in a stringstream and recovering it as a string?? That way string::size() would be the number of characters in the integer.

[Simonius]

The problem I'm having is determening the length of the integer.

Either I use a left allign and use a width of the ammount of digits of the largest counters +1.

Or I use a right allign of the ammount of digits of the largest result + 1.

But I don't know how to get how many digits the number is.