Thanks Laurent_R, this is useful information I hadn’t come across before. Is it documented anywhere? I don’t see anything in sprintf or the Camel Book, and the latest C Standard doesn’t seem to cover it either?

I actually once had to write a special rounding module just because my client considered the above to be simply wrong and wanted 2.5 to be rounded to 3.

Simply adding a minimum field width to the format seems to do the trick:

 1:03 >perl -wE "printf qq[%9f\t%.0f\t%2.0f\n], ($_ + 0.5) x 3 for 0 .
+. 10;"
 0.500000       0        1
 1.500000       2        2
 2.500000       2        3
 3.500000       4        4
 4.500000       4        5
 5.500000       6        6
 6.500000       6        7
 7.500000       8        8
 8.500000       8        9
 9.500000       10      10
10.500000       10      11

 1:03 >perl -v

This is perl 5, version 18, subversion 0 (v5.18.0) built for MSWin32-x
+86-multi-thread-64int

[download]

It should perhaps also be pointed out that where the internal representation of a floating point number is inexact, all bets are off:

 1:29 >perl -wE "printf qq[%21.18f\t%.1f\t%4.1f\n], ($_ + 0.05) x 3 fo
+r 0 .. 10;"
 0.050000000000000003   0.1      0.1
 1.050000000000000000   1.1      1.1
 2.049999999999999800   2.0      2.0
 3.049999999999999800   3.0      3.0
 4.049999999999999800   4.0      4.0
 5.049999999999999800   5.0      5.0
 6.049999999999999800   6.0      6.0
 7.049999999999999800   7.0      7.0
 8.050000000000000700   8.1      8.1
 9.050000000000000700   9.1      9.1
10.050000000000001000   10.1    10.1

 1:29 >

[download]

Cheers,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re^3: How to calculate the sum of columns to be equal to 100? by Athanasius
in thread How to calculate the sum of columns to be equal to 100? by Anonymous Monk

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