Re^2: Padding with sprintf changing number

I am not sure how things changed please see my output 1348 4887.15 -----> this is the line i copy pasted no operation Checking amnt before conversion 4887.15, Checking amnt after rounding 4887.15, Checking amnt after conversion 488715, 488714 i m checking amount before padding, 0000000000488714 i m checking amount after padding, why it


print " Checking amnt before conversion $amt,\n";
        $amt= sprintf("%.2f",$amt);
        print " Checking amnt after rounding $amt,\n";
        $amt = $amt*100;
        print " Checking amnt after conversion $amt,\n";

sub amnt($amn)
{
my $amount=$_[0];
$amount=int($amount);
say  "$amount i m checking amount before padding,\n";
#my $padamnt = sprintf("%016.0f",$amount);---> currently commented to 
+check integer effect.
my $padamnt = sprintf("%016d",$amount);

say  "$padamnt i m checking amount after padding,\n";
 return $padamnt;
}
[download]

Comment on Re^2: Padding with sprintf changing number Download Code

Replies are listed 'Best First'.
Re^3: Padding with sprintf changing number by syphilis (Archbishop) on Sep 27, 2021 at 14:26 UTC
I've rewritten your code into a form that I think makes at least some sense: use strict; use warnings; my $amt = 4887.15; print " Checking amnt before conversion $amt,\n"; $amt= sprintf("%.2f",$amt); print " Checking amnt after rounding $amt,\n"; $amt = $amt100; print " Checking amnt after conversion $amt,\n"; printf "Checking the EXACT value of amnt: %.17g\n", $amt; amnt($amt); sub amnt { my $amount=$_[0]; $amount=int($amount); print "$amount i m checking amount before padding,\n"; #my $padamnt = sprintf("%016.0f",$amount);---> currently commented to +check integer effect. my $padamnt = sprintf("%016d",$amount); print "$padamnt i m checking amount after padding,\n"; return $padamnt; } [download] When I run that script, I get: `Checking amnt before conversion 4887.15, Checking amnt after rounding 4887.15, Checking amnt after conversion 488715, Checking the EXACT value of amnt: 488714.99999999994 488714 i m checking amount before padding, 0000000000488714 i m checking amount after padding,` [download] Note that I've added a line of code that demonstrates that the EXACT value of $amt is NOT 488715. Perl's print() function frequently fails to produce an accurate representation of floating point values - and that's what is happening here. That output I'm seeing is as I expect. Which is the line of output that you don't understand ? You need to stay alert to this aspect of perl's print() function. Neither python3 nor raku are afflicted with such a poorly designed implementation: `$ python3 -c "print(4887.15 100)" 488714.99999999994 $ raku -e "say 4887.15e0 * 100" 488714.99999999994` [download] Cheers, Rob	[reply] [d/l] [select]
Re^4: Padding with sprintf changing number by choroba (Cardinal) on Sep 27, 2021 at 14:31 UTC
> Neither python3 nor raku But `$ python2 -c 'print(4887.15 * 100)' 488715.0` [download] `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]
Re^5: Padding with sprintf changing number by syphilis (Archbishop) on Sep 27, 2021 at 14:53 UTC
Yes, I had good reason to avoid mentioning python2's print() implementation ;-) It apparently rounds to even fewer decimal digits than perl5: `$ python2 -c 'print 2 0.5' 1.41421356237 $ perl -le 'print 2 0.5' 1.4142135623731` [download] At least they've done something about it. Maybe perl7 will do the same. Cheers, Rob	[reply] [d/l]


The stupid question is the question not asked
	PerlMonks