bigrat(3perl) | Perl Programmers Reference Guide | bigrat(3perl) |
bigrat - transparent big rational number support for Perl
use bigrat; print 2 + 4.5; # Math::BigRat 13/2 print 1/3 + 1/4; # Math::BigRat 7/12 print inf + 42; # Math::BigRat inf print NaN * 7; # Math::BigRat NaN print hex("0x1234567890123490"); # Perl v5.10.0 or later { no bigrat; print 1/3; # 0.33333... } # for older Perls, import into current package: use bigrat qw/hex oct/; print hex("0x1234567890123490"); print oct("01234567890123490");
All numeric literal in the given scope are converted to Math::BigRat objects.
All operators (including basic math operations) except the range operator ".." are overloaded.
So, the following:
use bigrat; $x = 1234;
creates a Math::BigRat and stores a reference to in $x. This happens transparently and behind your back, so to speak.
You can see this with the following:
perl -Mbigrat -le 'print ref(1234)'
Since numbers are actually objects, you can call all the usual methods from Math::BigRat on them. This even works to some extent on expressions:
perl -Mbigrat -le '$x = 1234; print $x->bdec()' perl -Mbigrat -le 'print 1234->copy()->binc();' perl -Mbigrat -le 'print 1234->copy()->binc->badd(6);' perl -Mbigrat -le 'print +(1234)->copy()->binc()'
(Note that print doesn't do what you expect if the expression starts with '(' hence the "+")
You can even chain the operations together as usual:
perl -Mbigrat -le 'print 1234->copy()->binc->badd(6);' 1241
Please note the following does not work as expected (prints nothing), since overloading of '..' is not yet possible in Perl (as of v5.8.0):
perl -Mbigrat -le 'for (1..2) { print ref($_); }'
"bigrat" recognizes some options that can be passed while loading it via "use". The following options exist:
perl -Mbigrat=a,50 -le 'print sqrt(20)'
Note that setting precision and accuracy at the same time is not possible.
perl -Mbigrat=p,-50 -le 'print sqrt(20)'
Note that setting precision and accuracy at the same time is not possible.
perl -Mbigrat=l,GMP -e 'print 2 ** 512' perl -Mbigrat=lib,GMP -e 'print 2 ** 512' perl -Mbigrat=try,GMP -e 'print 2 ** 512' perl -Mbigrat=only,GMP -e 'print 2 ** 512'
perl -Mbigrat=v
Math with the numbers is done (by default) by a backend library module called Math::BigInt::Calc. The default is equivalent to saying:
use bigrat lib => 'Calc';
you can change this by using:
use bigrat lib => 'GMP';
The following would first try to find Math::BigInt::Foo, then Math::BigInt::Bar, and if this also fails, revert to Math::BigInt::Calc:
use bigrat lib => 'Foo,Math::BigInt::Bar';
Using c<lib> warns if none of the specified libraries can be found and Math::BigInt fell back to one of the default libraries. To suppress this warning, use c<try> instead:
use bigrat try => 'GMP';
If you want the code to die instead of falling back, use "only" instead:
use bigrat only => 'GMP';
Please see the respective module documentation for further details.
Since all numbers are now objects, you can use all methods that are part of the Math::BigRat API.
But a warning is in order. When using the following to make a copy of a number, only a shallow copy will be made.
$x = 9; $y = $x; $x = $y = 7;
Using the copy or the original with overloaded math is okay, e.g., the following work:
$x = 9; $y = $x; print $x + 1, " ", $y,"\n"; # prints 10 9
but calling any method that modifies the number directly will result in both the original and the copy being destroyed:
$x = 9; $y = $x; print $x->badd(1), " ", $y,"\n"; # prints 10 10 $x = 9; $y = $x; print $x->binc(1), " ", $y,"\n"; # prints 10 10 $x = 9; $y = $x; print $x->bmul(2), " ", $y,"\n"; # prints 18 18
Using methods that do not modify, but test that the contents works:
$x = 9; $y = $x; $z = 9 if $x->is_zero(); # works fine
See the documentation about the copy constructor and "=" in overload, as well as the documentation in Math::BigFloat for further details.
# perl -Mbigrat=e -wle 'print e'
Returns Euler's number "e", aka exp(1).
# perl -Mbigrat=PI -wle 'print PI'
Returns PI.
bexp($power, $accuracy);
Returns Euler's number "e" raised to the appropriate power, to the wanted accuracy.
Example:
# perl -Mbigrat=bexp -wle 'print bexp(1,80)'
bpi($accuracy);
Returns PI to the wanted accuracy.
Example:
# perl -Mbigrat=bpi -wle 'print bpi(80)'
use bigrat; print "in effect\n" if bigrat::in_effect; # true { no bigrat; print "in effect\n" if bigrat::in_effect; # false }
Returns true or false if "bigrat" is in effect in the current scope.
This method only works on Perl v5.9.4 or later.
This means that arithmetic involving only string values or string literals are performed using Perl's built-in operators.
For example:
use bigrat; my $x = "900000000000000009"; my $y = "900000000000000007"; print $x - $y;
outputs 0 on default 32-bit builds, since "bigrat" never sees the string literals. To ensure the expression is all treated as "Math::BigRat" objects, use a literal number in the expression:
print +(0+$x) - $y;
use 5.010; for my $i (12..13) { for my $j (20..21) { say $i ** $j; # produces a floating-point number, # not an object } }
use bigrat qw/hex oct/; print hex("0x1234567890123456"); { no bigrat; print hex("0x1234567890123456"); }
The second call to hex() will warn about a non-portable constant.
Compare this to:
use bigrat; # will warn only under Perl older than v5.9.4 print hex("0x1234567890123456");
perl -Mbigrat -le 'print sqrt(33)' perl -Mbigrat -le 'print 2**255' perl -Mbigrat -le 'print 4.5+2**255' perl -Mbigrat -le 'print 3/7 + 5/7 + 8/3' perl -Mbigrat -le 'print 12->is_odd()'; perl -Mbigrat=l,GMP -le 'print 7 ** 7777'
Please report any bugs or feature requests to "bug-bignum at rt.cpan.org", or through the web interface at <https://rt.cpan.org/Ticket/Create.html?Queue=bignum> (requires login). We will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
You can find documentation for this module with the perldoc command.
perldoc bigrat
You can also look for information at:
<https://github.com/pjacklam/p5-bignum>
<https://rt.cpan.org/Dist/Display.html?Name=bignum>
<https://metacpan.org/release/bignum>
<http://matrix.cpantesters.org/?dist=bignum>
<https://cpanratings.perl.org/dist/bignum>
This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.
bignum and bigint.
Math::BigInt, Math::BigFloat, Math::BigRat and Math::Big as well as Math::BigInt::FastCalc, Math::BigInt::Pari and Math::BigInt::GMP.
2023-11-25 | perl v5.36.0 |