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Re: Printf/Sprintf Behavior Change

by McA (Priest)
on Sep 16, 2013 at 16:37 UTC ( #1054314=note: print w/replies, xml ) Need Help??

in reply to Printf/Sprintf Behavior Change


I'm pretty sure that your expectation of the result of

print sprintf("%0.02f",0.345);

is a little bit wrong. 0.345 rounded to two digits after the comma is 0.35 and not 0.34. You hit a classical floating point rounding error, Have a look at:

perl -E 'print sprintf("%0.18f",0.346);'

If you do mathematics with this kind of rounding error you can be hit by such a phaenomena.

UPDATE: Look at this:

#!/usr/bin/env perl use strict; use warnings; use 5.010; use Data::Dumper; my $l8 = 3.49; my $l7 = 2; my $subprice = 1.4; my $tprice; $tprice = ($l8/$l7)-$subprice; if ($tprice < 1 && length($tprice) > 4) { print "SPRINTF - $tprice - " . sprintf("%0.18f",$tprice) . "\n"; }


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[james28909]: thanks
[james28909]: what i am trying to do is track state of a chat based application. i need to be able to store the channels and such for a user, and when they join a new server/channel i need to be able to update that feild.
[james28909]: do you think OO would best suite that?
[karlgoethebier]: james28909: The last two are not mainstream. You have been warned ;-)
[karlgoethebier]: james28909: I don't know. Try it.

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