[Qt-interest] Cutting useless decimal places

[Atlant Schmidt]

Charly:

  Here's something to get you started / help us all
  think about your question.

  This produces the following output:

    0.000125346 -> 0.000
    0.001253457 -> 0.001
    0.012534568 -> 0.013
    0.125345679 -> 0.125
    1.253456789 -> 1.253
    12.534567890 -> 12.54
    125.345678900 -> 125.3
    1253.456789000 -> 1253
    12534.567890000 -> 12535
    12534.567800000 -> 12535
    12534.567000000 -> 12535
    12534.560000000 -> 12535
    12534.500000000 -> 12534
    12534.510000000 -> 12535
    12534.000000000 -> 12534
    602214178999999989284864.000000000 -> 602214178999999989284864

                 Atlant


#include <stdio.h>
#include <math.h>


// Forward routines
//

int  main(int argc, char **argv);
void try_one( double input );


int main(int argc, char **argv)
  {

    try_one( 0.0001253456789 );
    try_one( 0.001253456789 );
    try_one( 0.01253456789 );
    try_one( 0.1253456789 );
    try_one( 1.253456789 );
    try_one( 12.53456789 );
    try_one( 125.3456789 );
    try_one( 1253.456789 );
    try_one( 12534.56789 );
    try_one( 12534.5678 );
    try_one( 12534.567 );
    try_one( 12534.56 );
    try_one( 12534.5 );
    try_one( 12534.51 );
    try_one( 12534.0 );
    try_one( 6.02214179E23 );

    return 0;

  }


void try_one( double input )
  {

    double output;
    double absval;

    output = round(input*1000.0)/1000.0;
    absval = fabs( output );

    if      (absval<  10.0)
        printf( "%.9f -> %.3f\n", input, output );
    else if (absval< 100.0)
        printf( "%.9f -> %.2f\n", input, output );
    else if (absval<1000.0)
        printf( "%.9f -> %.1f\n", input, output );
    else
        printf( "%.9f -> %.0f\n", input, output );

  }



-----Original Message-----
From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of mailinglists at bluespirit.la
Sent: Monday, October 25, 2010 04:04
To: qt-interest at trolltech.com
Subject: [Qt-interest] Cutting useless decimal places

Hello,

a very simple question: How can I create a QString from a
float/double, in format 'f' without giving a explicit number of decimal
places to the arg() arguments?

qDebug() << QString("Hello world: %1").arg( fNumber, 0, 'f' );

When setting fNumbers to '0.125' I want an output of '0.125'. But when
setting the fNumbers variable to '200', I don't want an output of
"200.000". I want also use the localized output - so I prefer
QString::arg() to QString::sprintf(). The use of precision==-1 is not
documented - at least not in qt 4.6 api-doc.

Thank in advance,

Charly

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