Re^2: Help me make a test case for Math::BigFloat

[fizbin]

Yeah; I'll admit that once I pulled the code into a pretty format for the SOPW it stopped looking so ugly, convoluted, and in need of beating down into minimalness as it did when it was just four tight lines in my command window following a -e.

[xdg]

Along those lines, I'd suggest streamlining it even more and submitting it as a test file (i.e. use Test::More instead of print. For example:

use strict;
use warnings;
use Test::More tests => 3;
use bignum;

sub xe{
 $_[0]*log($_[0])+log(atan2(1,1)*8*$_[0])/2
  + 1/(12*$_[0]) - 1/(360*($_[0]**3)) + 1/(1260*($_[0]**5));
}

my ($m, $n, $r) = ( 2**96, 3*(10**6), 1*(10**6) );

my $e=exp(xe($m-$n)+xe($m-$r)-xe($m)-xe($m-$n-$r));

is( $e      , 1,    '$e should equal 1'     );
is( 1-$e    , 0,    '1-$e should equal 0'   );
is( 1-"$e"  , 0,    '1-"$e" should equal 0' );

Gives:

1..3
ok 1 - $e should equal 1
not ok 2 - 1-$e should equal 0
#     Failed test (bigtest.pl at line 17)
#          got: '1'
#     expected: '0'
ok 3 - 1-"$e" should equal 0
# Looks like you failed 1 test of 3.

That's even easier for a module author to work with.

[fizbin]

Good idea - thanks.

I eventually did find a way to simplify the math, and here's the test case I sent off:

#!perl
use strict;
use warnings;
use Test::More tests => 4;
use bignum;

my $lnev = -7 / (10**17);
my $ev=exp($lnev);

is( sprintf('%0.5f',$ev)     , '1.00000', '($ev) is approx. 1'     );
is( sprintf('%0.5f',1-$ev)   , '0.00000', '(1-$ev) is approx. 0'   );
is( sprintf('%0.5f',1-"$ev") , '0.00000', '(1-"$ev") is approx. 0' );

cmp_ok( $ev, '!=', 0, '$ev should not equal 0');

Note that by futzing with the $lnev number, you can get this bug to disappear - for example, by changing the "7" to a "1".

[xdg]

Note that by futzing with the $lnev number, you can get this bug to disappear.

I'd add that to the test case. I find it helpful to show both working and non-working variations. Easier to drill in on what's happening.