- **Perl Misc**
(*http://www.velocityreviews.com/forums/f67-perl-misc.html*)

- - **bignum::bdiv() not working correctly on integers**
(*http://www.velocityreviews.com/forums/t911673-bignum-bdiv-not-working-correctly-on-integers.html*)

bignum::bdiv() not working correctly on integersHi, I've recently discovered that if I create a "bignum" object in Perl and call the ->bdiv() method, sometimes the object will get modified and sometimes it won't. Here's a sample program that illustrates what I'm talking about: #!/usr/bin/perl use strict; use warnings; use bignum; my $n1 = 6.6; print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6.6 $n1->bdiv(2); print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3.3 print "\n"; my $n2 = 6; print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 $n2->bdiv(2); print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 6 (error?) __END__ I've tested this script on both Windows and Unix, and the output is the same. I changed "use bignum" to "use bigint" and I saw the expected 6, 3, and 6, 3 as output. (The floating-point numbers were truncated, but that's no surprise since we're working with integers.) I also changed "bdiv" to "bmul" (using the "bignum" module) and I saw the expected 6.6, 13.2, and 6, 12 as output, so apparently bignum::dmul() works consistently. I've noticed that bignum::bdiv() seems to modify the calling object if the value is a floating-point number (that is, cannot be represented as an integer). But if the calling object is an integer (even one with a decimal point like 6.0), then bignum::bdiv() does not modify it. I noticed that if I print out ref($n1) and ref($n2), I see that $n1 is a Math::BigFloat and that $n2 is a Math::BigInt. So I might think that the problem lies in the Math::BigInt module. However, when I change "use bignum" to "use bigint", they both become Math::BigInt objects, but now the bdiv() method is modifying the calling object (as I think it should). So it doesn't look like the problem is with Math::BigInt, but rather with the "bignum" module. Is this incosistent behavior of the "bignum" module a bug, or am I missing something? I haven't seen much code that uses the "bigint" and "bignum" modules, so as far as I know they're deprecated, but I haven't read anything to that effect. -- Jean-Luc |

Re: bignum::bdiv() not working correctly on integersjl_post@hotmail.com wrote:
> Hi, > > I've recently discovered that if I create a "bignum" object in Perl > and call the ->bdiv() method, sometimes the object will get modified > and sometimes it won't. Here's a sample program that illustrates what > I'm talking about: > > #!/usr/bin/perl > > use strict; > use warnings; > > use bignum; > > my $n1 = 6.6; > print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6.6 > $n1->bdiv(2); > print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3.3 > > print "\n"; > > my $n2 = 6; > print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 > $n2->bdiv(2); > print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 6 (error?) > > __END__ > > > I've tested this script on both Windows and Unix, and the output is > the same. I changed "use bignum" to "use bigint" and I saw the > expected 6, 3, and 6, 3 as output. (The floating-point numbers were > truncated, but that's no surprise since we're working with integers.) > > I also changed "bdiv" to "bmul" (using the "bignum" module) and I > saw the expected 6.6, 13.2, and 6, 12 as output, so apparently > bignum::dmul() works consistently. > > I've noticed that bignum::bdiv() seems to modify the calling object > if the value is a floating-point number (that is, cannot be > represented as an integer). But if the calling object is an integer > (even one with a decimal point like 6.0), then bignum::bdiv() does not > modify it. > > I noticed that if I print out ref($n1) and ref($n2), I see that $n1 > is a Math::BigFloat and that $n2 is a Math::BigInt. So I might think > that the problem lies in the Math::BigInt module. However, when I > change "use bignum" to "use bigint", they both become Math::BigInt > objects, but now the bdiv() method is modifying the calling object (as > I think it should). > > So it doesn't look like the problem is with Math::BigInt, but > rather with the "bignum" module. > > Is this incosistent behavior of the "bignum" module a bug, or am I > missing something? I haven't seen much code that uses the "bigint" > and "bignum" modules, so as far as I know they're deprecated, but I > haven't read anything to that effect. > > -- Jean-Luc bigint promotes the type to BigInt or BigFloat as required. When you start with a BigInt and divide by a float it must make a new bignum. You can see it explicitly by doing this: my $n1 = new Math::BigFloat 6; print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6 $n1->bdiv(2); print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3 print "\n"; my $n2 = new Math::BigInt 6; print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 $n2->bdiv(2); print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 6 (unexpected) |

Re: bignum::bdiv() not working correctly on integersOn Oct 28, 12:19 pm, Steve C <smallp...@juno.com> wrote:
> > bigint promotes the type to BigInt or BigFloat as required. > When you start with a BigInt and divide by a float it must make > a new bignum. You can see it explicitly by doing this: > > my $n1 = new Math::BigFloat 6; > print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6 > $n1->bdiv(2); > print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3 > > print "\n"; > > my $n2 = new Math::BigInt 6; > print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 > $n2->bdiv(2); > print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 6 (unexpected) That's not the behavior I'm getting. When I run your code in the following script: #!/usr/bin/perl use strict; use warnings; use Math::BigFloat; my $n1 = new Math::BigFloat 6; print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6 $n1->bdiv(2); print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3 print "\n"; use Math::BigInt; my $n2 = new Math::BigInt 6; print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 $n2->bdiv(2); print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 3 __END__ I see as output 6, 3 and 6, 3 (and not 6, 3, and 6, 6 like you saw). But even if Math::BigInt::bdiv() did make a new bignum, I'd still expect the bdiv() method to behave as documented in the "perldoc Math::BigInt" documentation, which is to change the value of the calling object. I noticed that just placing the "use bignum;" like anywhere in the script causes weird things to happen. Even if I put it in as the last line of my above script (but before the __END__ tag, of course) the output I see changes to 6, 6 and 6, 6. Did you have "use bignum;" (or "use bigint;") anywhere in your script? If you do, try removing it and running the script again. You might get different output. And in case anyone wants to know, "perl -v" gives me this output: On Windows: This is perl, v5.10.0 built for MSWin32-x86-multi-thread On Linux: This is perl, v5.8.4 built for i386-linux-thread-multi -- Jean-Luc |

Re: bignum::bdiv() not working correctly on integersjl_post@hotmail.com wrote:
> On Oct 28, 12:19 pm, Steve C <smallp...@juno.com> wrote: >> bigint promotes the type to BigInt or BigFloat as required. >> When you start with a BigInt and divide by a float it must make >> a new bignum. You can see it explicitly by doing this: >> >> my $n1 = new Math::BigFloat 6; >> print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6 >> $n1->bdiv(2); >> print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3 >> >> print "\n"; >> >> my $n2 = new Math::BigInt 6; >> print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 >> $n2->bdiv(2); >> print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 6 (unexpected) > > > That's not the behavior I'm getting. When I run your code in the > following script: > > > #!/usr/bin/perl > > use strict; > use warnings; > > use Math::BigFloat; > my $n1 = new Math::BigFloat 6; > print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6 > $n1->bdiv(2); > print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3 > > print "\n"; > > use Math::BigInt; > my $n2 = new Math::BigInt 6; > print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 > $n2->bdiv(2); > print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 3 > > __END__ > > > I see as output 6, 3 and 6, 3 (and not 6, 3, and 6, 6 like you saw). > > But even if Math::BigInt::bdiv() did make a new bignum, I'd still > expect the bdiv() method to behave as documented in the "perldoc > Math::BigInt" documentation, which is to change the value of the > calling object. > > I noticed that just placing the "use bignum;" like anywhere in the > script causes weird things to happen. Even if I put it in as the last > line of my above script (but before the __END__ tag, of course) the > output I see changes to 6, 6 and 6, 6. > > Did you have "use bignum;" (or "use bigint;") anywhere in your > script? If you do, try removing it and running the script again. You > might get different output. > > And in case anyone wants to know, "perl -v" gives me this output: > > On Windows: This is perl, v5.10.0 built for MSWin32-x86-multi-thread > > On Linux: This is perl, v5.8.4 built for i386-linux-thread-multi > > -- Jean-Luc I was explaining what bignum does. Math::BigInt and Math::BigFloat act as expected by themselves. Sorry I forgot to include the use bignum in my post. |

Re: bignum::bdiv() not working correctly on integersOn Oct 28, 12:49*pm, Steve C <smallp...@juno.com> wrote:
> > I was explaining what bignum does. *Math::BigInt and Math::BigFloat > act as expected by themselves. *Sorry I forgot to include the > use bignum in my post. Okay, but if I run my most-recently posted script with "use bignum;" I get 6, 6 and 6, 6. If I run it without that line I see 6, 3, and 6, 3. I still don't see how you got 6, 3, and 6, 6. Can you post the script you used? -- Jean-Luc |

Re: bignum::bdiv() not working correctly on integersjl_post@hotmail.com wrote:
> On Oct 28, 12:49 pm, Steve C <smallp...@juno.com> wrote: >> I was explaining what bignum does. Math::BigInt and Math::BigFloat >> act as expected by themselves. Sorry I forgot to include the >> use bignum in my post. > > > Okay, but if I run my most-recently posted script with "use > bignum;" I get 6, 6 and 6, 6. If I run it without that line I see 6, > 3, and 6, 3. I still don't see how you got 6, 3, and 6, 6. > > Can you post the script you used? > > -- Jean-Luc use bignum; my $n1 = new Math::BigFloat 6; print "\$n1 before \$n1->bdiv(2): $n1\n"; # prints 6 $n1->bdiv(2); print "\$n1 after \$n1->bdiv(2): $n1\n"; # prints 3 print "\n"; my $n2 = new Math::BigInt 6; print "\$n2 before \$n2->bdiv(2): $n2\n"; # prints 6 $n2->bdiv(2); print "\$n2 after \$n2->bdiv(2): $n2\n"; # prints 6 |

Re: bignum::bdiv() not working correctly on integersOn Oct 28, 12:19 pm, Steve C <smallp...@juno.com> wrote:
> > bigint promotes the type to BigInt or BigFloat as required. > When you start with a BigInt and divide by a float it must make > a new bignum. I disagree. When I run this code: #!/usr/bin/perl use strict; use warnings; use Math::BigInt; my $n = Math::BigInt->new(6); print "\$n before \$n->bdiv(2): $n\n"; # prints 6 print "\\\$n = ", \$n, "\n"; print "ref(\$n) = ", ref($n), "\n\n"; $n->bdiv(2); print "\$n after \$n->bdiv(2): $n\n"; # prints 3 print "\\\$n = ", \$n, "\n"; print "ref(\$n) = ", ref($n), "\n"; __END__ I see this output: $n before $n->bdiv(2): 6 \$n = REF(0x22c725c) ref($n) = Math::BigInt $n after $n->bdiv(2): 3 \$n = REF(0x22c725c) ref($n) = Math::BigInt So not only do I see 6 and 3 as output, I also see that $n is still the same object before as after the call to ->bdiv() (in other words, it never made a copy). Now I run the following script, which is identical to the previous one except that it has the "use bignum;" line at the bottom: #!/usr/bin/perl use strict; use warnings; use Math::BigInt; my $n = Math::BigInt->new(6); print "\$n before \$n->bdiv(2): $n\n"; # prints 6 print "\\\$n = ", \$n, "\n"; print "ref(\$n) = ", ref($n), "\n\n"; $n->bdiv(2); print "\$n after \$n->bdiv(2): $n\n"; # prints 6 (why?) print "\\\$n = ", \$n, "\n"; print "ref(\$n) = ", ref($n), "\n"; use bignum; __END__ Now I get this output: $n before $n->bdiv(2): 6 \$n = REF(0x99725c) ref($n) = Math::BigInt $n after $n->bdiv(2): 6 \$n = REF(0x99725c) ref($n) = Math::BigInt As before, $n is still the same object (that is, it was not replaced with a copy) and it's still a Math::BigInt object, but now the output is 6 and 6. Why is that? Why is just the simple inclusion of the "use bignum;" line enough to change the behavior of Math::BigInt::bdiv() ? "perldoc Math::BigInt" explicitly says that $n will be modified when calling the bdiv() method. If that's the case, why does the first script do just that but the second script does not? (There's nothing I found in the "perldoc bignum" documentation that says otherwise.) -- Jean-Luc |

All times are GMT. The time now is 02:51 AM. |

Powered by vBulletin®. Copyright ©2000 - 2014, vBulletin Solutions, Inc.

SEO by vBSEO ©2010, Crawlability, Inc.