keyboard event - C / C++ / MFC Discussion Boards

little_missy3-Feb-09 2:11

3-Feb-09 2:11

How do you make a program in C++ that computes for this:

e^x = 1 + (x/1!) + ([x^2]/2!) + ([x^3]/3!) + ... + ([x^n]/n!)

where e is the euler's contant, x is the input

there should be 500 addends (so n = 499)

Thank you Big Grin | :-D

Re: Euler's Contant To The X Power

toxcct3-Feb-09 2:34

toxcct

3-Feb-09 2:34

#include <cmath>
 
::exp(x);

also, you could have a look here[^]

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Re: Euler's Contant To The X Power

little_missy3-Feb-09 23:53

little_missy

3-Feb-09 23:53

I don't understand what I have to do with the link you gave me. I really need this tonight. Please please please help me. I'm a noob in C++

Re: Euler's Contant To The X Power

toxcct4-Feb-09 0:02

toxcct

4-Feb-09 0:02

I gave you the solution to get it calculated easily, by using the exp() function.

the link was an additional tip to see it used in a real context.

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Re: Euler's Contant To The X Power

cmk3-Feb-09 6:09

cmk

3-Feb-09 6:09

You need to use a bignum library to calc the large exponents/factorals and maintain precision.

http://en.wikipedia.org/wiki/Arbitrary-precision_arithmetic[^]

...cmk

The idea that I can be presented with a problem, set out to logically solve it with the tools at hand, and wind up with a program that could not be legally used because someone else followed the same logical steps some years ago and filed for a patent on it is horrifying.
- John Carmack

Re: Euler's Contant To The X Power

Luc Pattyn3-Feb-09 6:21

Luc Pattyn

3-Feb-09 6:21

Hi,

this is elementary.

as always, express each term of the series as a product of the previous term and some factors;
that will give you:
- the most efficient way to perform the calculations
- the fact that the terms decrease as soon as n exceeds x
- a reasonable test for early termination of the series (for small x that is)

there is no need for special libraries, just use doubles.

Smile | :)

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Re: Euler's Contant To The X Power

cmk3-Feb-09 21:12

cmk

3-Feb-09 21:12

(S)He stated (s)he wants to expand to ~500.
(S)He will likely exceed the precision of a double by the mid teens.

keyboard event

hrishiS3-Feb-09 1:18

hrishiS

3-Feb-09 1:18

Hi everyone...
Could anyone please tell me how to check for an keyboard event in win32 consol application...
I have an while loop
while(1)
{
}

I need to check each time if I have pressed a particular key....say "h"

Thanks in advance

I am a learner Always

Re: keyboard event

CPallini3-Feb-09 1:40

CPallini

3-Feb-09 1:40

Are you looking for this [^]?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: keyboard event

hrishiS3-Feb-09 1:46

hrishiS

3-Feb-09 1:46

thanks...
But those are blocked call.....I want something like this...
My while loop keeps running.....and it checks for a key...if it was pressd it exits....But if it wasnot pressed also, my while loop keep running(iterating..)
Basically i need a nonblocking function....asynchronous

Thanks

I am a learner Always

Re: keyboard event

CPallini3-Feb-09 2:05

CPallini

3-Feb-09 2:05

See here [^].
Smile | :)

Re: keyboard event

Stuart Dootson3-Feb-09 2:06

Stuart Dootson

3-Feb-09 2:06

You could try using _kbhit[^].

Re: keyboard event

Nibu babu thomas3-Feb-09 2:03

Nibu babu thomas

3-Feb-09 2:03

himangshuS wrote:
I need to check each time if I have pressed a particular key....say "h"

Use _kbhit() in combination with getch().

Nibu babu thomas
Microsoft MVP for VC++

Code must be written to be read, not by the compiler, but by another human being.

Programming Blog: http://nibuthomas.wordpress.com

Re: keyboard event

hrishiS3-Feb-09 2:42

hrishiS

3-Feb-09 2:42

thanks...

I am a learner Always

Platform SDK: Get domain name

Stefan Spenz3-Feb-09 1:18

Stefan Spenz

3-Feb-09 1:18

I need to get the domain name for the currently logged on user.
::GetUserName gets me the user name, but how do I get the domain name for that user?

Thanks!

Re: Platform SDK: Get domain name

Supriya Tonape3-Feb-09 1:43

Supriya Tonape

3-Feb-09 1:43

With, Win32_LogonSession you will get 'LogonId' use this logonId to query the Win32_LoggedOnUser. After querying 'Win32_LoggedOnUser' you will get all the fields, like - Domain, Name etc

Supriya

Re: Platform SDK: Get domain name

Stuart Dootson3-Feb-09 1:59

Stuart Dootson

3-Feb-09 1:59

Use NetWkstaUserGetInfo[^] and retrieve level 1 information, as below. Requires Windows NT 3.1, 2000, XP, Vista.

#include <Windows.h>
#include <lm.h>

std::wstring GetDomainName()
{
   WKSTA_USER_INFO_1* workstationInfo;
   const NET_API_STATUS status = NetWkstaUserGetInfo(NULL, 1, (LPBYTE*)&workstationInfo);
   if (status == NERR_Success)
   {
      return workstationInfo->wkui1_logon_domain;
      NetApiBufferFree((LPBYTE*)&workstationInfo);
   }
   return std::wstring();
}

Re: Platform SDK: Get domain name

krmed3-Feb-09 2:01

krmed

3-Feb-09 2:01

Another option is the environment variables USERDNSDOMAIN and USERDOMAIN.

Hope that helps.

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

Memory Leaks With CString in vc6.0 in Release mode

Ramasani3-Feb-09 1:05

Ramasani

3-Feb-09 1:05

I am facing a run time problem with the CString in Release builds in vc6.0
i observed that the memory wont be released for cstring object i checked in the task manager can any one help for this here i posted the code also

#include "stdafx.h"
#include "afx.h"
#include "afxwin.h"

#include <windows.h>
#include "fixalloc.h"

#pragma warning (disable:4786)
#pragma warning (disable:4503)
#include<list>
#include<string>
#include<vector>

using namespace std;

#include <afxtempl.h>

void test()
{
vector<CString> stldmlist;
CString a;

FILE *fp=fopen("E:\\log1.txt","r");
char str[1000];

while(!feof(fp))
{
fscanf(fp,"%s\n",str);
a=str;
stldmlist.push_back(a);
}
fclose(fp);

AfxMessageBox("Memory");
}

UINT32 main(int argc, char* argv[])
{
CString obj;
AfxMessageBox("Start ");
test();
AfxMessageBox("End");
return 1;
}

Hi this Ravinder

Re: Memory Leaks With CString in vc6.0 in Release mode

Stuart Dootson3-Feb-09 1:12

Stuart Dootson

3-Feb-09 1:12

Ramasani wrote:
memory wont be released for cstring object i checked in the task manager

Given that task manager doesn't tell you if objects released memory or not, I presume you were looking at an process's working set...

The behaviour I'm guessing you're talking about (the process's working set rising and not falling after test exits) is to be expected - when you start allocating memory, the C runtime requests large chunks of memory from the Windows memory manager. It will not necessarily bother releasing them when you release objects, as allocating and releasing memory with the Windows memory manager is quite expensive.

Re: Memory Leaks With CString in vc6.0 in Release mode

Ramasani3-Feb-09 1:21

Ramasani

3-Feb-09 1:21

if i go for more number of CString calls it returns memory leak errors(no memory) is there any patches available for this? i need very urgent.

Hi this Ravinder

Re: Memory Leaks With CString in vc6.0 in Release mode

Stuart Dootson3-Feb-09 2:03

Stuart Dootson

3-Feb-09 2:03

Ramasani wrote:
memory leak errors(no memory)

Ummm - 'no memory' does not necessarily imply memory leaks. It could just be that you're allocating a *lot* of memory. How big is this log file you're reading in?

Ramasani wrote:
is there any patches available for this?

Let's think about this - what's more likely to be at fault - MFC/C++ standard libraries or your code/understanding thereof? Mmmm.

Re: Memory Leaks With CString in vc6.0 in Release mode

Ramasani3-Feb-09 2:10

Ramasani

3-Feb-09 2:10

Actually i am using CString in my application more than 10k times and my apllication will run for days in this cases memory is not releasing thats the problem i have given a sample code only but it is working fine in Debug mode not in release mode ?

Hi this Ravinder

Re: Memory Leaks With CString in vc6.0 in Release mode

Stuart Dootson3-Feb-09 2:37

Stuart Dootson

3-Feb-09 2:37

Ramasani wrote:
it is working fine in Debug mode not in release mode

In what sense? You have not stated a) what you expected to observe when running in release mode and b) what actually did happen.

I've run your sample code (admittedly built with VS2003 rather than VC6) and monitored the execution of both debug and release variants with task manager and Process Explorer[^]. In both cases, it behaved exactly as I would expect.

Re: Memory Leaks With CString in vc6.0 in Release mode

Ramasani3-Feb-09 2:43

Ramasani

3-Feb-09 2:43

yeh., Exactly its working in vs2003 and later but not vc6.0 my applications all are in vc6.0. i need patches without changing my application

Hi this Ravinder

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