[C++] Number to String

[Blackout]

I've tried several methods and now I've gotten all confused :wacko: .

So I have a number inside a string. Let's take, for example, "200." Now, I want to convert the string into a long and divide it by 2 then store it back inside a string. I tried using ostringstream, but couldn't get it to work correctly.

Does anyone know what to do?

[kjordan2001]

int a;

string somestring = "200";

stringstream s(somestring, stringstream::in | stringstream::out);

s >> a;

[Blackout]

So where in that code can it divide by 2? And also, how can I append

  Quote

stringstream s(somestring, stringstream::in | stringstream::out);

into another string? I tried

  Quote

newString += s

newString is a string from string.h.

Edited January 22, 2005 by Blackout

[kjordan2001]

Hmm, guess I should have read more closely...

Converting it is still the same, just replace int with long and to convert it back after you divide:

stringstream ss;

string str;

ss << somenumber;

ss >> str;

[Lenny]

You cannot use any addition operator on a string as it's not a numerical type.

You need to convert newString to a number itself, add s the convert that back to a string.

atoi is a simple function for converting a string to a number.

Here's a link to msdn, you can look it up there. data conversion routines

[kjordan2001]

  Lenny said:

You cannot use any addition operator on a string as it's not a numerical type.

You need to convert newString to a number itself, add s the convert that back to a string.

atoi is a simple function for converting a string to a number.

Here's a link to msdn, you can look it up there. data conversion routines

585338566[/snapback]

You can use + on strings, but he's trying to do it with a string and a stringstream. It should be newString += someOtherString;

And as for those types of data conversion, they aren't in the standard, whereas the way I posted uses more standard methods and more probably safer too.

[Blackout]

  kjordan2001 said:

Hmm, guess I should have read more closely...

Converting it is still the same, just replace int with long and to convert it back after you divide:

stringstream ss;

string str;

ss << somenumber;

ss >> str;

585338552[/snapback]

Well I was trying to append, not copy the stringstream over to the string.

  Lenny said:

You cannot use any addition operator on a string as it's not a numerical type.

You need to convert newString to a number itself, add s the convert that back to a string.

atoi is a simple function for converting a string to a number.

Here's a link to msdn, you can look it up there. data conversion routines

585338566[/snapback]

Is atoi a C++ standard or is it only available in VC++? Because on MSDN it says that it's part of the VC++ runtime libraries...

[kjordan2001]

  Blackout said:

Well I was trying to append, not copy the stringstream over to the string.

Is atoi a C++ standard or is it only available in VC++? Because on MSDN it says that it's part of the VC++ runtime libraries...

585338706[/snapback]

I'm not sure I get what you're trying to do, are you trying to divide a number in a string by 2 and store it back into a string and then append it? If so:

long a;

string s = "200";

stringstream ss(s,stringstream::in | stringstream::out);

ss >> a;

a = a/2.0;

stringstream ss2;

ss2 << a;

string str;

ss2 >> str;

atoi isn't part of the C++ standard, although it's included in Linux as well.

[Blackout]

Here's what I'm trying to do:

1) I have a string called "num." For example, "200." I have another string called "result."

2) I want to take "num" and convert it to a long so I can divide it by 2.

3) So now "num" equals "100." Now I want to take the "num" and APPEND it to "result."

  Quote

ss2 >> str;

Doesn't that code copy the string over rather than append?

My problem with appending "100" is that when I take a number and append it to a string, it converts the number by treating it as an ASCII value.

So basically, the question is: how do I append a number to a string without it being treated as an ASCII value? Because it keeps getting converted to the ASCII character equivalent of the value, but I just want it to append the value.

Edited January 22, 2005 by Blackout

[kjordan2001]

Heh, forgot to append str, here we go again:

string num = "200";

int number;

stringstream num_convert(num,stringstream::in | stringstream::out);

num_convert >> number;

number = number/2;

stringstream string_convert;

string_convert << number;

string str;

string_convert >> str;

string result = "Result is: ";

result += str;

[Blackout]

Okay, thanks! It finally works!

[kjordan2001]

Also, one of the best parts of stringstream is it can convert a string to anything (that is if it's possible to convert it to that type). No need for all those extra functions. And it also goes the other way, anything to string.