From michael at potter.name  Fri Apr 27 18:54:33 2012
From: michael at potter.name (Michael Potter)
Date: Fri, 27 Apr 2012 21:54:33 -0400
Subject: [Chicago-talk] (no subject)
Message-ID: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>

Monks,

I am looking for a graceful way to round numbers.

The following program
#!/bin/perl

sub myround
{
   my $src = shift;
   printf("%.2f\n", $src);
}

myround("1.335");
myround("0.335");

outputs this:
$ perl ./round.pl
1.33
0.34

I know why.  It has to do with the well known side effects of using
floating point.

What I don't know is a graceful way to round.

I would like to use something that already comes with perl and void
adding any modules.

-- 
potter

From joel.a.berger at gmail.com  Fri Apr 27 21:09:20 2012
From: joel.a.berger at gmail.com (Joel Berger)
Date: Fri, 27 Apr 2012 23:09:20 -0500
Subject: [Chicago-talk] (no subject)
In-Reply-To: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
References: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
Message-ID: <CAAMA-9OUvcUJzcA_-diF2YobSm_GCTHCbN5AAXAixUopA61NFA@mail.gmail.com>

Perhaps I'm mistaken about something, but it should "round half to even".
Still, if you look up round in perlfaq4 it gives a little more information
about what you are seeing (perldoc -q round).

You may have to take its advice and implement your own rounding algorithm,
but I'm sure there must be something on CPAN for this.

Joel

On Fri, Apr 27, 2012 at 8:54 PM, Michael Potter <michael at potter.name> wrote:

> Monks,
>
> I am looking for a graceful way to round numbers.
>
> The following program
> #!/bin/perl
>
> sub myround
> {
>   my $src = shift;
>   printf("%.2f\n", $src);
> }
>
> myround("1.335");
> myround("0.335");
>
> outputs this:
> $ perl ./round.pl
> 1.33
> 0.34
>
> I know why.  It has to do with the well known side effects of using
> floating point.
>
> What I don't know is a graceful way to round.
>
> I would like to use something that already comes with perl and void
> adding any modules.
>
> --
> potter
> _______________________________________________
> Chicago-talk mailing list
> Chicago-talk at pm.org
> http://mail.pm.org/mailman/listinfo/chicago-talk
>
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From imranjj at gmail.com  Fri Apr 27 21:26:35 2012
From: imranjj at gmail.com (imran javaid)
Date: Fri, 27 Apr 2012 23:26:35 -0500
Subject: [Chicago-talk] (no subject)
In-Reply-To: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
References: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
Message-ID: <CACgL-nLaL3VhiWkTG4HbBCogW+TbfGNCCZ_jfWrPMbbeFVC_mA@mail.gmail.com>

I haven't tested this for all cases, but this should fix the issue for most
cases:

sub myround2 {
  my $src = shift;
  my $pre = shift;
  print int($src * 10**$pre + .5)/100;
  print "\n";
}

myround2("1.335",2);
myround2("0.335",2);
myround2("1.334999999999999",2);
myround2("0.334999999999999",2);

-imran

On Fri, Apr 27, 2012 at 8:54 PM, Michael Potter <michael at potter.name> wrote:

> Monks,
>
> I am looking for a graceful way to round numbers.
>
> The following program
> #!/bin/perl
>
> sub myround
> {
>   my $src = shift;
>   printf("%.2f\n", $src);
> }
>
> myround("1.335");
> myround("0.335");
>
> outputs this:
> $ perl ./round.pl
> 1.33
> 0.34
>
> I know why.  It has to do with the well known side effects of using
> floating point.
>
> What I don't know is a graceful way to round.
>
> I would like to use something that already comes with perl and void
> adding any modules.
>
> --
> potter
> _______________________________________________
> Chicago-talk mailing list
> Chicago-talk at pm.org
> http://mail.pm.org/mailman/listinfo/chicago-talk
>
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From imranjj at gmail.com  Fri Apr 27 21:29:36 2012
From: imranjj at gmail.com (imran javaid)
Date: Fri, 27 Apr 2012 23:29:36 -0500
Subject: [Chicago-talk] (no subject)
In-Reply-To: <CACgL-nLaL3VhiWkTG4HbBCogW+TbfGNCCZ_jfWrPMbbeFVC_mA@mail.gmail.com>
References: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
	<CACgL-nLaL3VhiWkTG4HbBCogW+TbfGNCCZ_jfWrPMbbeFVC_mA@mail.gmail.com>
Message-ID: <CACgL-nKXRnrKy3bgXX0JzPethNVbxT1uDvwVV9AfiWuQEf44Kg@mail.gmail.com>

doesn't work for negative number, btw. need to check the sign in that case.

On Fri, Apr 27, 2012 at 11:26 PM, imran javaid <imranjj at gmail.com> wrote:

> I haven't tested this for all cases, but this should fix the issue for
> most cases:
>
> sub myround2 {
>   my $src = shift;
>   my $pre = shift;
>   print int($src * 10**$pre + .5)/100;
>   print "\n";
> }
>
> myround2("1.335",2);
> myround2("0.335",2);
> myround2("1.334999999999999",2);
> myround2("0.334999999999999",2);
>
> -imran
>
> On Fri, Apr 27, 2012 at 8:54 PM, Michael Potter <michael at potter.name>wrote:
>
>> Monks,
>>
>> I am looking for a graceful way to round numbers.
>>
>> The following program
>> #!/bin/perl
>>
>> sub myround
>> {
>>   my $src = shift;
>>   printf("%.2f\n", $src);
>> }
>>
>> myround("1.335");
>> myround("0.335");
>>
>> outputs this:
>> $ perl ./round.pl
>> 1.33
>> 0.34
>>
>> I know why.  It has to do with the well known side effects of using
>> floating point.
>>
>> What I don't know is a graceful way to round.
>>
>> I would like to use something that already comes with perl and void
>> adding any modules.
>>
>> --
>> potter
>> _______________________________________________
>> Chicago-talk mailing list
>> Chicago-talk at pm.org
>> http://mail.pm.org/mailman/listinfo/chicago-talk
>>
>
>
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From michael at potter.name  Sat Apr 28 06:39:36 2012
From: michael at potter.name (Michael Potter)
Date: Sat, 28 Apr 2012 09:39:36 -0400
Subject: [Chicago-talk] (no subject)
In-Reply-To: <CACgL-nKXRnrKy3bgXX0JzPethNVbxT1uDvwVV9AfiWuQEf44Kg@mail.gmail.com>
References: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
	<CACgL-nLaL3VhiWkTG4HbBCogW+TbfGNCCZ_jfWrPMbbeFVC_mA@mail.gmail.com>
	<CACgL-nKXRnrKy3bgXX0JzPethNVbxT1uDvwVV9AfiWuQEf44Kg@mail.gmail.com>
Message-ID: <CAEKW2O+M_H-UJ5vC67io8dFvaPMLxWuuWci8bqvRK98Q+hvMZg@mail.gmail.com>

I ended up using the Math::Decimal module:

my $rounded = dec_round("NEAR_AWZ", $unrounded, "0.01");

Limited testing indicated that that matched the rounding of excel.

AWZ means away from zero.



On Sat, Apr 28, 2012 at 12:29 AM, imran javaid <imranjj at gmail.com> wrote:
> doesn't work for negative number, btw. need to check the sign in that case.
>
>
> On Fri, Apr 27, 2012 at 11:26 PM, imran javaid <imranjj at gmail.com> wrote:
>>
>> I haven't tested this for all cases, but this should fix the issue for
>> most cases:
>>
>> sub myround2 {
>> ? my $src = shift;
>> ? my $pre = shift;
>> ? print int($src * 10**$pre + .5)/100;
>> ? print "\n";
>> }
>>
>> myround2("1.335",2);
>> myround2("0.335",2);
>> myround2("1.334999999999999",2);
>> myround2("0.334999999999999",2);
>>
>> -imran
>>
>> On Fri, Apr 27, 2012 at 8:54 PM, Michael Potter <michael at potter.name>
>> wrote:
>>>
>>> Monks,
>>>
>>> I am looking for a graceful way to round numbers.
>>>
>>> The following program
>>> #!/bin/perl
>>>
>>> sub myround
>>> {
>>> ? my $src = shift;
>>> ? printf("%.2f\n", $src);
>>> }
>>>
>>> myround("1.335");
>>> myround("0.335");
>>>
>>> outputs this:
>>> $ perl ./round.pl
>>> 1.33
>>> 0.34
>>>
>>> I know why. ?It has to do with the well known side effects of using
>>> floating point.
>>>
>>> What I don't know is a graceful way to round.
>>>
>>> I would like to use something that already comes with perl and void
>>> adding any modules.
>>>
>>> --
>>> potter
>>> _______________________________________________
>>> Chicago-talk mailing list
>>> Chicago-talk at pm.org
>>> http://mail.pm.org/mailman/listinfo/chicago-talk
>>
>>
>
>
> _______________________________________________
> Chicago-talk mailing list
> Chicago-talk at pm.org
> http://mail.pm.org/mailman/listinfo/chicago-talk



-- 
Michael Potter
? Tapp Solutions, LLC
? Replatform Technologies, LLC
+1 770 815 6142 ?** Atlanta?** michael at potter.name ?**
www.linkedin.com/in/michaelpotter

From danel at speakeasy.net  Sat Apr 28 13:14:40 2012
From: danel at speakeasy.net (Alexander Danel)
Date: Sat, 28 Apr 2012 15:14:40 -0500
Subject: [Chicago-talk] (no subject)
In-Reply-To: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
References: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
Message-ID: <033c01cd257b$8b331bc0$a1995340$@speakeasy.net>

The correct way to round numbers in Perl is "printf()" and "sprintf()".

Note that rounding is something that makes sense to humans but not to
computers.  Computers are binary, they don't care about our decimal
concepts, unless we ask them to.  The times when decimal numbers matter is
during input (from a human) and output (for a human.)  Therefore, it is
appropriate that the Perl method for rounding is an output (or string)
function.

Alexander Danel

-----Original Message-----
From: chicago-talk-bounces+danel=speakeasy.net at pm.org
[mailto:chicago-talk-bounces+danel=speakeasy.net at pm.org] On Behalf Of
Michael Potter
Sent: Friday, April 27, 2012 8:55 PM
To: Chicago.pm chatter
Subject: [Chicago-talk] (no subject)

Monks,

I am looking for a graceful way to round numbers.

The following program
#!/bin/perl

sub myround
{
   my $src = shift;
   printf("%.2f\n", $src);
}

myround("1.335");
myround("0.335");

outputs this:
$ perl ./round.pl
1.33
0.34

I know why.  It has to do with the well known side effects of using floating
point.

What I don't know is a graceful way to round.

I would like to use something that already comes with perl and void adding
any modules.

--
potter
_______________________________________________
Chicago-talk mailing list
Chicago-talk at pm.org
http://mail.pm.org/mailman/listinfo/chicago-talk


From dcmertens.perl at gmail.com  Sat Apr 28 13:27:58 2012
From: dcmertens.perl at gmail.com (David Mertens)
Date: Sat, 28 Apr 2012 15:27:58 -0500
Subject: [Chicago-talk] (no subject)
In-Reply-To: <033c01cd257b$8b331bc0$a1995340$@speakeasy.net>
References: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
	<033c01cd257b$8b331bc0$a1995340$@speakeasy.net>
Message-ID: <CA+4ieYXz=91W7yz7D-a4-DsHdKL5AXVJXCD7ZtBFAB5cG22+Jg@mail.gmail.com>

On Sat, Apr 28, 2012 at 3:14 PM, Alexander Danel <danel at speakeasy.net>wrote:

> The correct way to round numbers in Perl is "printf()" and "sprintf()".
>
> Note that rounding is something that makes sense to humans but not to
> computers.  Computers are binary, they don't care about our decimal
> concepts, unless we ask them to.  The times when decimal numbers matter is
> during input (from a human) and output (for a human.)  Therefore, it is
> appropriate that the Perl method for rounding is an output (or string)
> function.
>
> Alexander Danel
>

Your observation that rounding really only makes sense with a string output
is a good point that I had never quite realized. However, printf and
sprintf do not give you much control over the rounding details (which,
though esoteric, are important). In case you missed it, Michael posted that
he found a CPAN module that gave him exactly what he needed, called
Math::Decimal.

David

 -----Original Message-----
> From: chicago-talk-bounces+danel=speakeasy.net at pm.org
> [mailto:chicago-talk-bounces+danel=speakeasy.net at pm.org] On Behalf Of
> Michael Potter
> Sent: Friday, April 27, 2012 8:55 PM
> To: Chicago.pm chatter
> Subject: [Chicago-talk] (no subject)
>
> Monks,
>
> I am looking for a graceful way to round numbers.
>
> The following program
> #!/bin/perl
>
> sub myround
> {
>   my $src = shift;
>   printf("%.2f\n", $src);
> }
>
> myround("1.335");
> myround("0.335");
>
> outputs this:
> $ perl ./round.pl
> 1.33
> 0.34
>
> I know why.  It has to do with the well known side effects of using
> floating
> point.
>
> What I don't know is a graceful way to round.
>
> I would like to use something that already comes with perl and void adding
> any modules.
>
> --
> potter
> _______________________________________________
> Chicago-talk mailing list
> Chicago-talk at pm.org
> http://mail.pm.org/mailman/listinfo/chicago-talk
>
> _______________________________________________
> Chicago-talk mailing list
> Chicago-talk at pm.org
> http://mail.pm.org/mailman/listinfo/chicago-talk
>



-- 
 "Debugging is twice as hard as writing the code in the first place.
  Therefore, if you write the code as cleverly as possible, you are,
  by definition, not smart enough to debug it." -- Brian Kernighan
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From andy at petdance.com  Sat Apr 28 19:06:58 2012
From: andy at petdance.com (Andy Lester)
Date: Sat, 28 Apr 2012 21:06:58 -0500
Subject: [Chicago-talk] (no subject)
In-Reply-To: <CA+4ieYXz=91W7yz7D-a4-DsHdKL5AXVJXCD7ZtBFAB5cG22+Jg@mail.gmail.com>
References: <CAEKW2OJA0UhAZfGygDWL+=Bu7PMjoX6UYxFVyRWgA=URPOBO-w@mail.gmail.com>
	<033c01cd257b$8b331bc0$a1995340$@speakeasy.net>
	<CA+4ieYXz=91W7yz7D-a4-DsHdKL5AXVJXCD7ZtBFAB5cG22+Jg@mail.gmail.com>
Message-ID: <924E8ADB-15CB-4138-B60C-36658330627E@petdance.com>


On Apr 28, 2012, at 3:27 PM, David Mertens wrote:

> On Sat, Apr 28, 2012 at 3:14 PM, Alexander Danel <danel at speakeasy.net> wrote:
> The correct way to round numbers in Perl is "printf()" and "sprintf()".


perldoc -q round

perldoc -q says "Search the FAQ".

xoa

--
Andy Lester => andy at petdance.com => www.petdance.com => AIM:petdance

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