• 0

[C++] Number to String


Question

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?

Link to comment
https://www.neowin.net/forum/topic/274948-c-number-to-string/
Share on other sites

11 answers to this question

Recommended Posts

  • 0

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 by Blackout
  • 0

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

  • 0
  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.

  • 0
  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...

  • 0
  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.

  • 0

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 by Blackout
  • 0

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;

This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Posts

    • They always have. This just updates what's included out of the box during the initial install.
    • So basically their prebuilding it into the ISOs?
    • Microsoft shares Defender anti-virus update for new Windows 11/10 ISOs by Sayan Sen Following the one for Lumma last month, Microsoft has also published a new Defender update for Windows 11/10/Server installation images this month. This update package is necessary as a Windows installation image may contain old, outdated anti-malware definitions and software binaries. Aside from better security, these updates can also provide improved performance benefits in some cases. When a new Windows installation is set up, there may be a temporary security risk due to outdated Microsoft Defender protection in the OS installation images. This happens because the antimalware software included in these images might not be up to date. Thus Microsoft says that these updated definitions essentially help close this protection gap. Microsoft delivered the latest security definitions for Windows images via security intelligence update version 1.431.54.0. The Defender package version is also the same. It applies to Windows 11, Windows 10 (Enterprise, Pro, and Home editions), Windows Server 2022, Windows Server 2019, and Windows Server 2016. Microsoft writes: From Microsoft's security bulletin, we learn that the security intelligence update version 1.431.54.0 was released this past week adds threat detections for various backdoor exploits, trojans, among others. For those wondering, the latest intelligence update is version 1.431.155.0 at the time of writing.
    • “In other news about OneDrive frustration, Microsoft recently locked out a user who was attempting to move a bunch of important data from old hard drives to OneDrive.” - It was probably CSMA..
    • Just what I needed! An extremely expensive pair of sunglasses that I will lose and cannot use indoors. My life will be complete. I trust Meta AI watching my entire life happen. It's going to be the best ever!
  • Recent Achievements

    • One Month Later
      SekTheFirst earned a badge
      One Month Later
    • First Post
      zayanhani earned a badge
      First Post
    • First Post
      HarryTaylor earned a badge
      First Post
    • One Year In
      Eternal Tech earned a badge
      One Year In
    • One Month Later
      Eternal Tech earned a badge
      One Month Later
  • Popular Contributors

    1. 1
      +primortal
      651
    2. 2
      ATLien_0
      233
    3. 3
      Michael Scrip
      226
    4. 4
      Steven P.
      140
    5. 5
      +FloatingFatMan
      139
  • Tell a friend

    Love Neowin? Tell a friend!