Re: Negative zero? There's gotta be a sprintf that undoes that, right?

Revised: using %g doesn't work as expected
Round, then format. Here, I use sprintf with "%.5f" to round to five decimal places, and then use your "%7.5f" to format it.

print "print an example of negative zero\n";
my @range = (-0.0000001, -0.000001, -0.00001, -0.0001);

foreach my $example (@range)
{
    my $twice = sprintf "%.5f", $example;
    my $tret = sprintf("rounded float:%7.5f, other:%7.5e",$twice,$twic
+e);
    
    print "The Number $example is represented as $tret\n";
}
[download]

Output:

print an example of negative zero
The Number -1e-007 is represented as rounded float:0.00000, other:0.00
+000e+000
The Number -1e-006 is represented as rounded float:0.00000, other:0.00
+000e+000
The Number -1e-005 is represented as rounded float:-0.00001, other:-1.
+00000e-005
The Number -0.0001 is represented as rounded float:-0.00010, other:-1.
+00000e-004
[download]

Caution: Contents may have been coded under pressure.

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Re^2: Negative zero? There's gotta be a sprintf that undoes that, right? by rgiskard (Hermit) on Dec 11, 2007 at 19:47 UTC
No wait, I'm not getting the same output using the rounding twice solution. Roy Johnson... what version of perl are you using? I'm on 5.8.5, RHLinux `print "print an example of negative zero\n"; @range = (-0.0000001, -0.000001, -0.00001, -0.0001); foreach $example (@range) { my $preround = sprintf ("%.5f",$example); my $tret = sprintf("rounded float:%7.5f \n",$preround); print "The Number $example is represented as $tret, here's the rou +nded num $preround\n"; }` [download] Output: print an example of negative zero The Number -1e-07 is represented as rounded float:-0.00000 , here's the rounded num -0.00000 The Number -1e-06 is represented as rounded float:-0.00000 , here's the rounded num -0.00000 The Number -1e-05 is represented as rounded float:-0.00001 , here's the rounded num -0.00001 The Number -0.0001 is represented as rounded float:-0.00010 , here's the rounded num -0.00010	[reply] [d/l]
Re^3: Negative zero? There's gotta be a sprintf that undoes that, right? by Roy Johnson (Monsignor) on Dec 12, 2007 at 19:17 UTC
That's weird. I'm using ActivePerl 5.8.1. But I just tried it on 5.8.6 for Solaris, and got your result there. The fix is to add zero: `my $preround = 0 + sprintf ("%.5f",$example);` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re^2: Negative zero? There's gotta be a sprintf that undoes that, right? by rgiskard (Hermit) on Dec 11, 2007 at 18:58 UTC
Schweet! This solves my sprintf dilemma without additional subroutines (and then having to package + implement + distribute + maintain said subroutines). Thanks!	[reply]