Convert string to double problem _tstof

[Anonymous]

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

[Alexander.Rivilis]

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.

[Anonymous]

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

[Alexander.Rivilis]

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@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

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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. 

[Anonymous]

Hi,

Understood that ...

Which data format is used for replace this source.

With Regards,

Vijay

[Alexander.Rivilis]

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?

[Alexander.Rivilis]

  // - 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

[Anonymous]

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?

[Anonymous]

// - 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?

[Alexander.Rivilis · Accepted solution]

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

[Alexander.Rivilis]

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@Anonymous wrote:

Expect Output is

But I want 2.4

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

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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 ???

[Anonymous]

Ok

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;

[Alexander.Rivilis]

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

[Anonymous]

Yes Correct!

I want 2.4

not 2.3999999

replies _tstof() ==> this function 

[Alexander.Rivilis]

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@Anonymous wrote:

I want 2.4

not 2.3999999

replies _tstof() ==> this function 

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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

[tbrammer]

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.

[Alexander.Rivilis]

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@tbrammer wrote:

I salute you for your patience, Alexander.

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