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Mail Archives: djgpp/2002/04/24/01:00:07

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From: "Alex Vinokur" <alexvn AT bigfoot DOT com>
Newsgroups: comp.lang.c++,comp.os.msdos.djgpp
Subject: Re: setw & notation
Date: Wed, 24 Apr 2002 07:57:12 +0200
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"Alan Didey" <a_didey AT hotmail DOT com> wrote in message news:3CC59DBB DOT 1000201 AT hotmail DOT com...

[snip]

|
| This program prints numbers without their fractional part (though
| rounded not truncated), or if they are smaller than one, prints only the
| first non-zero decimal place.  You have to calculate the precision
| required to do this yourself.  Note the use of epsilon() - this is
| important.
|
| #include <iostream>
| #include <limits>
| #include <iomanip>
| #include <cmath>
| using namespace std;
|
| int main()
| {
|      // remember the original format of the stream
|      ios_base::fmtflags flags = cout.flags();
|      streamsize prec = cout.precision();
|
|      // we never want scientific notation
|      cout.setf(ios_base::fixed, ios_base::floatfield);
|
|      // my implementation won't ever print more than 18 decimal places
|      for (double d=100000000000000.0; d>=1e-18; d/=10.0) {
| if(d < 1)
|     cout.precision(
| // enough precision for one decimal place
| static_cast<streamsize>(
|     -log10(d) + 1 - numeric_limits<double>::epsilon()
|     )
| );
| else // don't print fractional part of numbers greater than 1
|     cout.precision(0);
| cout << d << '\n';
|      }
|
|      // force the output on to the screen
|      cout.flush();
|
|      // restore the stream to its former glory
|      cout.precision(prec);
|      cout.setf(ios_base::fmtflags(0), ios_base::floatfield);
| }
|
| Its output:

[snip]

|
| 0.1
| 0.01
| 0.001
| 0.0001
| 0.00001
| 0.000001
| 0.0000001
| 0.00000001
| 0.000000001
| 0.0000000001
| 0.00000000001
| 0.000000000001
| 0.0000000000001
| 0.00000000000001
| 0.000000000000001
| 0.0000000000000001
| 0.00000000000000001
| 0.000000000000000001
|
|
[snip]

Thanks. It is almost OK.
The only thing I want to change is to see output as following :
        0.1
      0.01
    0.001
  0.0001
0.00001
............


Thanks in advance,

====================
  Alex Vinokur
    http://up.to/alexvn
    http://go.to/alexv_math
    mailto:alexvn AT bigfoot DOT com
    mailto:alexvn AT go DOT to
  ====================





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