Re: Rounding over numbers

TMTOWTDI. Here’s a general approach using sprintf:

#! perl
use strict;
use warnings;
use Test::More;

while (<DATA>)
{
    my ($decimals, $source, $target) = / (\d+) \D+ ([\d.]+) \D+ ([\d.]
++) /x;

    my  $result = round($source, $decimals);

    is($result, $target, "round $source to $target");
}

done_testing();

sub round
{
    my ($num, $decimals) = @_;

    return sprintf("%.*f0", $decimals, $num);
}

__DATA__
1 1.24 to 1.20
1 13.25 to 13.30
1 2.90 to 2.90
1 2.99 to 3.00
1 2.92 to 2.90
1 14 to 14.00
5 1.2345678 to 1.234570
[download]

Output:

16:05 >perl 1544_SoPW.pl
ok 1 - round 1.24 to 1.20
ok 2 - round 13.25 to 13.30
ok 3 - round 2.90 to 2.90
ok 4 - round 2.99 to 3.00
ok 5 - round 2.92 to 2.90
ok 6 - round 14 to 14.00
ok 7 - round 1.2345678 to 1.234570
1..7

16:05 >
[download]

Hope that helps,

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

Comment on Re: Rounding over numbers Select or Download Code

Replies are listed 'Best First'.

Re^2: Rounding over numbers
by kevbot (Vicar) on Feb 15, 2016 at 06:49 UTC

ok 1 - round 1.24 to 1.20
not ok 2 - round 13.25 to 13.30
#   Failed test 'round 13.25 to 13.30'
#   at r2.pl line 12.
#          got: '13.20'
#     expected: '13.30'
ok 3 - round 2.90 to 2.90
ok 4 - round 2.99 to 3.00
ok 5 - round 2.92 to 2.90
ok 6 - round 14 to 14.00
ok 7 - round 1.2345678 to 1.234570
1..7
# Looks like you failed 1 test of 7.
[download]

[reply]
[d/l]

Re^3: Rounding over numbers

by Laurent_R (Canon) on Feb 15, 2016 at 07:25 UTC

There may also be a difference with the libraries used. IEEE recommendation is to round the trailing "5" digit up or down depending on whether the previous digit is odd or even, but some libraries may still round up systematically.

Can you perhaps try again with 1325/100 to see if it makes a difference?

[reply]

Re^3: Rounding over numbers

by Athanasius (Archbishop) on Feb 15, 2016 at 07:03 UTC

Interesting. What is your system?

For the record, I’m running Strawberry Perl 5.22.1 under Windows 8.1 (64-bit). But it also tests successfully on my Strawberry Perl versions 5.12.3, 5.14.4, 5.18.2, and 5.22.0. The first two of these are 32-bit builds; the rest are 64-bit.

Update: Added info on 32- and 64-bit perl builds.

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

[reply]

Re^4: Rounding over numbers

by kevbot (Vicar) on Feb 15, 2016 at 07:23 UTC

Mac OS X (El Capitan, 10.11.3) using a perlbrew perl (v5.22.1)
Mac OS X (El Capitan, 10.11.3) system perl (v5.18.2)
Ubuntu (precise, 12.04.5 LTS) using a perlbrew perl (v5.16.2)
Ubuntu (precise, 12.04.5 LTS) system perl (v5.14.2)

UPDATE: I forgot to mention that all of these are 64-bit.

[reply]


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