bignum.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "bignum 3"
.TH bignum 3 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
bignum \- Transparent BigNumber support for Perl
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use bignum;
\&
\&  $x = 2 + 4.5,"\en";                    # BigFloat 6.5
\&  print 2 ** 512 * 0.1,"\en";            # really is what you think it is
\&  print inf * inf,"\en";                 # prints inf
\&  print NaN * 3,"\en";                   # prints NaN
\&
\&  {
\&    no bignum;
\&    print 2 ** 256,"\en";                # a normal Perl scalar now
\&  }
\&
\&  # for older Perls, note that this will be global:
\&  use bignum qw/hex oct/;
\&  print hex("0x1234567890123490"),"\en";
\&  print oct("01234567890123490"),"\en";
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
All operators (including basic math operations) are overloaded. Integer and
floating-point constants are created as proper BigInts or BigFloats,
respectively.
.PP
If you do
.PP
.Vb 1
\&        use bignum;
.Ve
.PP
at the top of your script, Math::BigFloat and Math::BigInt will be loaded
and any constant number will be converted to an object (Math::BigFloat for
floats like 3.1415 and Math::BigInt for integers like 1234).
.PP
So, the following line:
.PP
.Vb 1
\&        $x = 1234;
.Ve
.PP
creates actually a Math::BigInt and stores a reference to in \f(CW$x\fR.
This happens transparently and behind your back, so to speak.
.PP
You can see this with the following:
.PP
.Vb 1
\&        perl \-Mbignum \-le \*(Aqprint ref(1234)\*(Aq
.Ve
.PP
Don't worry if it says Math::BigInt::Lite, bignum and friends will use Lite
if it is installed since it is faster for some operations. It will be
automatically upgraded to BigInt whenever necessary:
.PP
.Vb 1
\&        perl \-Mbignum \-le \*(Aqprint ref(2**255)\*(Aq
.Ve
.PP
This also means it is a bad idea to check for some specific package, since
the actual contents of \f(CW$x\fR might be something unexpected. Due to the
transparent way of bignum \f(CW\*(C`ref()\*(C'\fR should not be necessary, anyway.
.PP
Since Math::BigInt and BigFloat also overload the normal math operations,
the following line will still work:
.PP
.Vb 1
\&        perl \-Mbignum \-le \*(Aqprint ref(1234+1234)\*(Aq
.Ve
.PP
Since numbers are actually objects, you can call all the usual methods from
BigInt/BigFloat on them. This even works to some extent on expressions:
.PP
.Vb 4
\&        perl \-Mbignum \-le \*(Aq$x = 1234; print $x\->bdec()\*(Aq
\&        perl \-Mbignum \-le \*(Aqprint 1234\->copy()\->binc();\*(Aq
\&        perl \-Mbignum \-le \*(Aqprint 1234\->copy()\->binc\->badd(6);\*(Aq
\&        perl \-Mbignum \-le \*(Aqprint +(1234)\->copy()\->binc()\*(Aq
.Ve
.PP
(Note that print doesn't do what you expect if the expression starts with
\&'(' hence the \f(CW\*(C`+\*(C'\fR)
.PP
You can even chain the operations together as usual:
.PP
.Vb 2
\&        perl \-Mbignum \-le \*(Aqprint 1234\->copy()\->binc\->badd(6);\*(Aq
\&        1241
.Ve
.PP
Under bignum (or bigint or bigrat), Perl will \*(L"upgrade\*(R" the numbers
appropriately. This means that:
.PP
.Vb 2
\&        perl \-Mbignum \-le \*(Aqprint 1234+4.5\*(Aq
\&        1238.5
.Ve
.PP
will work correctly. These mixed cases don't do always work when using
Math::BigInt or Math::BigFloat alone, or at least not in the way normal Perl
scalars work.
.PP
If you do want to work with large integers like under \f(CW\*(C`use integer;\*(C'\fR, try
\&\f(CW\*(C`use bigint;\*(C'\fR:
.PP
.Vb 2
\&        perl \-Mbigint \-le \*(Aqprint 1234.5+4.5\*(Aq
\&        1238
.Ve
.PP
There is also \f(CW\*(C`use bigrat;\*(C'\fR which gives you big rationals:
.PP
.Vb 2
\&        perl \-Mbigrat \-le \*(Aqprint 1234+4.1\*(Aq
\&        12381/10
.Ve
.PP
The entire upgrading/downgrading is still experimental and might not work
as you expect or may even have bugs. You might get errors like this:
.PP
.Vb 2
\&        Can\*(Aqt use an undefined value as an ARRAY reference at
\&        /usr/local/lib/perl5/5.8.0/Math/BigInt/Calc.pm line 864
.Ve
.PP
This means somewhere a routine got a BigFloat/Lite but expected a BigInt (or
vice versa) and the upgrade/downgrad path was missing. This is a bug, please
report it so that we can fix it.
.PP
You might consider using just Math::BigInt or Math::BigFloat, since they
allow you finer control over what get's done in which module/space. For
instance, simple loop counters will be Math::BigInts under \f(CW\*(C`use bignum;\*(C'\fR and
this is slower than keeping them as Perl scalars:
.PP
.Vb 1
\&        perl \-Mbignum \-le \*(Aqfor ($i = 0; $i < 10; $i++) { print ref($i); }\*(Aq
.Ve
.PP
Please note the following does not work as expected (prints nothing), since
overloading of '..' is not yet possible in Perl (as of v5.8.0):
.PP
.Vb 1
\&        perl \-Mbignum \-le \*(Aqfor (1..2) { print ref($_); }\*(Aq
.Ve
.Sh "Options"
.IX Subsection "Options"
bignum recognizes some options that can be passed while loading it via use.
The options can (currently) be either a single letter form, or the long form.
The following options exist:
.IP "a or accuracy" 2
.IX Item "a or accuracy"
This sets the accuracy for all math operations. The argument must be greater
than or equal to zero. See Math::BigInt's \fIbround()\fR function for details.
.Sp
.Vb 1
\&        perl \-Mbignum=a,50 \-le \*(Aqprint sqrt(20)\*(Aq
.Ve
.Sp
Note that setting precision and accurary at the same time is not possible.
.IP "p or precision" 2
.IX Item "p or precision"
This sets the precision for all math operations. The argument can be any