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output string formatting

pdorai
pdorai asked
on
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Last Modified: 2010-04-10
Hi, in C one uses " %4.3lf " to string format a long double floating point value. And " %4.3f " for ordinary floating point values.

What is its  equivalent in C++ ? (i.e. for long double string formating)

I tried using setprecision(4), but this messes up the output which returns with a string of # signs and some alphanumeric characters.

setprecision() is meant for normal/ordinary floating point values, but I don't know which is the equivalent parameter for long double floating point values .

Thanks

Paul
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Commented:
WxW, I think pdorai is trying to use streams.  Thus, the converting back to the C way is not a good idea.

setprecision(4) is not 100% equiviliant to C's %4.3f.  the precision is used in two ways.  If the stream is in automatic format or scientific format, then it will display 4 significant digits.  If the stream is in fixed format it will display 4 decimal digits.  You may need to set the width prior to ouputing the number to get the desired result.  

Commented:
In my opinion is every C function also a C++ function - but i think that's bad karma, right?

Commented:
Yes, but in many cases C++ provides improved ways to perform tasks that are not available in C.  C++'s I/O streams are an example.  They are more powerful and are much safer to use.  
WxW

Commented:
C++ streams are more powerful than printf and sprintf ?
For creating simple buffers ... I think that they are better & easier

Commented:
Here's a couple of ways!

CString text; //string???
float value = 1.30;
text.Format("$%7.2f", value);
(I like the above because you can easily see the formatting AND you are not changing the setup for cout)
or

cout.precision(4);
cout << 1.3456;

or

ios_base::fixed

etc...


Commented:
#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
      long double x;
      x = 12.3456;
      cout << setprecision(2) << fixed << setw(5) << x <<endl;
      return (0);
}
Is this what you want?
fixed is fixed decimal point
setprecision, as mentioned above, sets number of digits AFTER decimal point
setw sets the width to 5, this width INCLUDES the decimal point
Good luck
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