topic Re: Convert string to double problem _tstof in ObjectARX Forum

Convert string to double problem _tstof

Anonymous — Mon, 29 Aug 2016 09:52:30 GMT

Hi Friend,

I am convert string to double problem,

CString strValue=_T("2.4");

double dValue = _tstof(strValue);

Output is

Current Output

dValue result is 2.39999999

Expected Output

but I want dValue result is 2.4

With Regards,

Vijay

Re: Convert string to double problem _tstof

Alexander.Rivilis — Mon, 29 Aug 2016 13:38:08 GMT

Please read about floating (double) value precision: https://en.wikipedia.org/wiki/Double-precision_floating-point_format

It is OK if instead 2.4 you see 2.399999999999... because maximum precision of double value is 16 digit.

Re: Convert string to double problem _tstof

Anonymous — Tue, 30 Aug 2016 05:35:14 GMT

Hi, Ok but I want dValue result is 2.4 Which data format is used... CString strValue=_T("2.4"); double dValue = _tstof(strValue); Result is 2.399999 Expect is 2.4 Regards, Vijay

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 05:51:46 GMT

@Anonymous wrote:
Hi, Ok but I want dValue result is 2.4 Which data format is used... CString strValue=_T("2.4"); double dValue = _tstof(strValue); Result is 2.399999 Expect is 2.4 Regards, Vijay

It is look like you did not understood me or did not read about precision of double value and how double value stored in memory. Not all double value can be stored in memory (or register) exactly as you write as string.

Re: Convert string to double problem _tstof

Anonymous — Tue, 30 Aug 2016 06:44:57 GMT

Hi,

Understood that ...

Which data format is used for replace this source.

With Regards,

Vijay

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 08:11:12 GMT

Sorry but I did not understood what you want. Perhaps someone else will understand you and can help you. Is this question has any relation to ObjectARX?

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 08:24:24 GMT

  // - ArxProject4.TestDouble command (do not rename)
  static void ArxProject4TestDouble(void)
  {
    CString strValue=_T("2.4");
    double dValue = _tstof(strValue);
    CString strNewValue; strNewValue.Format(_T("%g"), dValue);
    acutPrintf(_T("\nstrNewValue=%s"), LPCTSTR(strNewValue));
  }

Command: TESTDOUBLE

strNewValue=2.4

Re: Convert string to double problem _tstof

Anonymous — Tue, 30 Aug 2016 09:14:34 GMT

Output is

Current Output

dValue result is 2.39999999

Expected Output

but I want dValue result is 2.4

Here dValue is double datatype

I want result in double

Expected :

dValue is 2.4

Value are store in double data type not string format.

Other then string which datatype is used?

Re: Convert string to double problem _tstof

Anonymous — Tue, 30 Aug 2016 09:34:44 GMT

// - ArxProject4.TestDouble command (do not rename)
static void ArxProject4TestDouble(void)
{
CString strValue=_T("2.4");
double dValue = _tstof(strValue);
acutPrintf(_T("\ndValue =%f"), dValue );
}

Current Output

dValue = 2.399999..

Expect Output is

But I want 2.4

double dValue = _tstof(strValue); \\ Replace is _tstof, to get expect result?

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 09:36:40 GMT

http://www.binaryconvert.com/convert_double.html

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 09:54:32 GMT

@Anonymous wrote:

Expect Output is

But I want 2.4

double dValue = _tstof(strValue); \\ Replace is _tstof, to get expect result?

You'll never get the "expected result", since double value can never be exactly the same as 2.4000000000000000000000000

Nearest value, which can be in double format is 2.39999999999999991118215802999E0

I clearly explained ???

Re: Convert string to double problem _tstof

Anonymous — Tue, 30 Aug 2016 09:55:43 GMT

CString strValue=_T("2.4");

i want to read the strValue value is 2.4.
2.4 value is store into any datatype for multiplication process.[Using _tstof this is problem]
which convert is possible?

current output:

Example:

double dValue = 2.399999999 * 2;
dValue = 4.8;

Want output

Example:

double dValue = 2.4 * 2;

dValue = 4.8;

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 10:07:05 GMT

It is look like I can not help you. Sorry.

Re: Convert string to double problem _tstof

Anonymous — Tue, 30 Aug 2016 10:18:46 GMT

Yes Correct!

I want 2.4

not 2.3999999

replies _tstof() ==> this function

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 10:28:01 GMT

@Anonymous wrote:

I want 2.4

not 2.3999999

replies _tstof() ==> this function

There is no function which can you use instead of _tstof() because double value can not have exact value 2.4

Every function which convert string "2.4" to double will be return value 2.39999999999999991118215802999E0 as more possible nearest to 2.4

Re: Convert string to double problem _tstof

tbrammer — Tue, 30 Aug 2016 16:20:39 GMT

I salute you for your patience, Alexander.

@sn.vijayan: You can't always get what you want.

You can't put a horse into a matchbox.

You can't put 2.4 into a double.

Accept it as it is.

Re: Convert string to double problem _tstof

Alexander.Rivilis — Tue, 30 Aug 2016 16:26:49 GMT

@tbrammer wrote:

I salute you for your patience, Alexander.

I was always told that I have an iron patience. I am glad that you appreciated it.