Re: Fortran-like number formatting

Roedy Green <see_website@[EMAIL PROTECTED]
> writes:
>In the olden days Fortran had something called G format.  It would
>display a number in minimum space, e.g. 7.6 but would revert to
>scientfic notation when it had to.

public class Main
{ public static void main( final java.lang.String[] args ) 
  { for( double v = java.lang.Math.PI * 1e4; v >= 1e-5; v /= 10 )
    java.lang.System.out.printf( "%.2g%n", v ); }}

3,1e+04
3,1e+03
3,1e+02
31
3,1
0,31
0,031
0,0031
0,00031
3,1e-05

  The documentation for »%g« on

http://download.java.net/jdk7/docs/api/java/util/Formatter.html#syntax

  seems to be insufficient:

      »'g', 'G'

      floating point

      The result is formatted using computerized scientific
      notation or decimal format, depending on the precision and
      the value after rounding.«

  The documentation for »%g« in

ISO/IEC 9899:1999 (E)

  is more detailed:

      »g,G 

      A double argument representing a floating-point number is
      converted in style f or e (or in style F or E in the case
      of a G conversion specifier), with the precision
      specifying the number of significant digits. If the
      precision is zero, it is taken as 1.

      The style used depends on the value converted; style e (or
      E) is used only if the exponent resulting from such a
      conversion is less than -4 or greater than or equal to the
      precision.«

  Either Sun Microsystems, Inc. expects the programmer to look
  into ISO/IEC 9899:1999 (E) for »%g«, or there is a more
  detailed description by Sun Microsystems, Inc., which I just
  have not found yet.