File Coverage

blib/lib/Math/BigInt/Lite.pm

Criterion	Covered	Total	%
statement	471	689	68.3
branch	279	556	50.1
condition	97	221	43.8
subroutine	103	121	85.1
pod	91	93	97.8
total	1041	1680	61.9

# For speed and simplicity, a Math::BigInt::Lite object is a reference to a
# scalar. When something more complex needs to happen (like +inf,-inf, NaN or
# rounding), Math::BigInt::Lite objects are upgraded.

package Math::BigInt::Lite;

require 5.006001;

use strict;
use warnings;

require Exporter;
use Scalar::Util qw< blessed >;

use Math::BigInt;

our ($_trap_inf, $_trap_nan);

our @ISA = qw(Math::BigInt Exporter);
our @EXPORT_OK = qw/objectify/;
my $class = 'Math::BigInt::Lite';

our $VERSION = '0.30';

##############################################################################
# global constants, flags and accessory

our $accuracy   = undef;
our $precision  = undef;
our $round_mode = 'even';
our $div_scale  = 40;
our $upgrade    = 'Math::BigInt';
our $downgrade  = undef;

my $nan = 'NaN';

my $MAX_NEW_LEN;
my $MAX_MUL;
my $MAX_ADD;

my $MAX_BIN_LEN = 31;
my $MAX_OCT_LEN = 10;
my $MAX_HEX_LEN =  7;

BEGIN {
    my $e0 = 1;
    my $e1 = $e0 + 1;
    my $num;
    {
        $num = '9' x $e1;       # maximum value in base 10**$e1
        $num = $num * $num      # multiply by itself
               + ($num - 1);    # largest possible carry
        last if $num !~ /^9{$e0}89{$e1}$/;      # check digit pattern
        $e0 = $e1;
        $e1++;
        redo;
    }
    my $e = $e0;                # $e1 is one too large

    # the limits below brush the problems with the test above under the rug:

    # the test should be able to find the proper $e automatically
    $e = 5 if $^O =~ /^uts/;    # UTS get's some special treatment
    $e = 5 if $^O =~ /^unicos/; # unicos is also problematic (6 seems to work
                                # there, but we play safe)
    $e = 8 if $e > 8;           # cap, for VMS, OS/390 and other 64 bit systems

    my $bi = $e;

    #  # determine how many digits fit into an integer and can be safely added
    #  # together plus carry w/o causing an overflow
    #
    #  # this below detects 15 on a 64 bit system, because after that it becomes
    #  # 1e16  and not 1000000 :/ I can make it detect 18, but then I get a lot of
    #  # test failures. Ugh! (Tomake detect 18: uncomment lines marked with *)
    #  use integer;
    #  my $bi = 5;                   # approx. 16 bit
    #  $num = int('9' x $bi);
    #  # $num = 99999; # *
    #  # while ( ($num+$num+1) eq '1' . '9' x $bi)   # *
    #  while ( int($num+$num+1) eq '1' . '9' x $bi)
    #    {
    #    $bi++; $num = int('9' x $bi);
    #    # $bi++; $num *= 10; $num += 9;     # *
    #    }
    #  $bi--;                                # back off one step

    # we ensure that every number created is below the length for the add, so
    # that it is always safe to add two objects together
    $MAX_NEW_LEN = $bi;
    # The constant below is used to check the result of any add, if above, we
    # need to upgrade.
    $MAX_ADD = int("1E$bi");
    # For mul, we need to check *before* the operation that both operands are
    # below the number benlow, since otherwise it could overflow.
    $MAX_MUL = int("1E$e");

    # print "MAX_NEW_LEN $MAX_NEW_LEN MAX_ADD $MAX_ADD MAX_MUL $MAX_MUL\n\n";
}

##############################################################################
# we tie our accuracy/precision/round_mode to BigInt, so that setting it here
# will do it in BigInt, too. You can't use Lite w/o BigInt, anyway.

sub round_mode {
    no strict 'refs';
    # make Class->round_mode() work
    my $self = shift;
    my $class = ref($self) || $self || __PACKAGE__;
    if (defined $_[0]) {
        my $m = shift;
        die "Unknown round mode $m"
          if $m !~ /^(even|odd|\+inf|\-inf|zero|trunc|common)$/;
        # set in BigInt, too
        Math::BigInt->round_mode($m);
        return ${"${class}::round_mode"} = $m;
    }
    return ${"${class}::round_mode"};
}

sub accuracy {
    # $x->accuracy($a);           ref($x) $a
    # $x->accuracy();             ref($x)
    # Class->accuracy();          class
    # Class->accuracy($a);        class $a

    my $x = shift;
    my $class = ref($x) || $x || __PACKAGE__;

    no strict 'refs';
    # need to set new value?
    if (@_ > 0) {
        my $a = shift;
        die ('accuracy must not be zero') if defined $a && $a == 0;
        if (ref($x)) {
            # $object->accuracy() or fallback to global
            $x->bround($a) if defined $a;
            $x->{_a} = $a;      # set/overwrite, even if not rounded
            $x->{_p} = undef;   # clear P
        } else {
            # set global
            Math::BigInt->accuracy($a);
            # and locally here
            $accuracy = $a;
            $precision = undef; # clear P
        }
        return $a;              # shortcut
    }

    if (ref($x)) {
        # $object->accuracy() or fallback to global
        return $x->{_a} || ${"${class}::accuracy"};
    }
    return ${"${class}::accuracy"};
}

sub precision {
    # $x->precision($p);          ref($x) $p
    # $x->precision();            ref($x)
    # Class->precision();         class
    # Class->precision($p);       class $p

    my $x = shift;
    my $class = ref($x) || $x || __PACKAGE__;

    no strict 'refs';
    # need to set new value?
    if (@_ > 0) {
        my $p = shift;
        if (ref($x)) {
            # $object->precision() or fallback to global
            $x->bfround($p) if defined $p;
            $x->{_p} = $p;      # set/overwrite, even if not rounded
            $x->{_a} = undef;   # clear A
        } else {
            Math::BigInt->precision($p);
            # and locally here
            $accuracy = undef;  # clear A
            $precision = $p;
        }
        return $p;              # shortcut
    }

    if (ref($x)) {
        # $object->precision() or fallback to global
        return $x->{_p} || ${"${class}::precision"};
    }
    return ${"${class}::precision"};
}

use overload
  '+'     => sub {
                 my $x = $_[0];
                 my $y = $_[1];
                 my $class = ref $x;
                 $y = $class->new($y) unless ref($y);
                 if ($y->isa($class)) {
                     $x = \($$x + $$y);
                     bless $x, $class;
                     $x = $upgrade->new($$x) if abs($$x) >= $MAX_ADD;
                 } else {
                     $x = $upgrade->new($$x)->badd($y);
                 }
                 $x;
             },

  '*'     => sub {
                 my $x = $_[0];
                 my $y = $_[1];
                 my $class = ref $x;
                 $y = $class->new($y) unless ref($y);
                 if ($y->isa($class)) {
                     $x = \($$x * $$y);
                     $$x = 0 if $$x eq '-0';      # correct 5.x.x bug
                     bless $x, $class;            # inline copy
                 } else {
                     $x = $upgrade->new(${$_[0]})->bmul($y);
                 }
             },

  # some shortcuts for speed (assumes that reversed order of arguments is routed
  # to normal '+' and we thus can always modify first arg. If this is changed,
  # this breaks and must be adjusted.)
  #'/='    =>      sub { scalar $_[0]->bdiv($_[1]); },
  #'*='    =>      sub { $_[0]->bmul($_[1]); },
  #'+='    =>      sub { $_[0]->badd($_[1]); },
  #'-='    =>      sub { $_[0]->bsub($_[1]); },
  #'%='    =>      sub { $_[0]->bmod($_[1]); },
  #'&='    =>      sub { $_[0]->band($_[1]); },
  #'^='    =>      sub { $_[0]->bxor($_[1]); },
  #'|='    =>      sub { $_[0]->bior($_[1]); },
  #'**='   =>      sub { $upgrade->bpow($_[0], $_[1]); },

  '<=>'   => sub { my $cmp = $_[0] -> bcmp($_[1]);
                   defined($cmp) && $_[2] ? -$cmp : $cmp; },

  '""'    => sub { "${$_[0]}"; },

  '0+'    => sub { ${$_[0]}; },

  '++'    => sub {
                 ${$_[0]}++;
                 return $upgrade->new(${$_[0]}) if ${$_[0]} >= $MAX_ADD;
                 $_[0];
             },

  '--'    => sub {
                 ${$_[0]}--;
                 return $upgrade->new(${$_[0]}) if ${$_[0]} <= -$MAX_ADD;
                 $_[0];
             },
  # fake HASH reference, so that Math::BigInt::Lite->new(123)->{sign} works
  '%{}'   => sub {
                 {
                     sign => ($_[0] < 0) ? '-' : '+',
                 };
             },
    ;

BEGIN {
    *objectify = \&Math::BigInt::objectify;
}

sub config {
    my $class = shift;

    # config({a => b, ...}) -> config(a => b, ...)
    @_ = %{ $_[0] } if @_ == 1 && ref($_[0]) eq 'HASH';

    # Getter/accessor.

    if (@_ == 1) {
        my $param = shift;

        # We don't use a math backend library.
        return if ($param eq 'lib' ||
                   $param eq 'lib_version');

        return $class -> SUPER::config($param);
    }

    # Setter.

    $class -> SUPER::config(@_) if @_;

    # For backwards compatibility.

    my $cfg = Math::BigInt -> config();
    $cfg->{version}     = $VERSION;
    $cfg->{lib}         = undef;
    $cfg->{lib_version} = undef;
    $cfg;
}

sub bgcd {

    # Convert calls like Class::method(2) into Class->method(2). It ignores
    # cases like Class::method($x), where $x is an object, because this is
    # indistinguishable from $x->method().

    unless (@_ && (ref($_[0]) || $_[0] =~ /^[a-z]\w*(?:::[a-z]\w*)*$/i)) {
        #carp "Using ", (caller(0))[3], "() as a function is deprecated;",
        #  " use is as a method instead" if warnings::warnif("deprecated");
        unshift @_, __PACKAGE__;
    }

    # Make sure each argument is an object.

    my ($class, @args) = objectify(0, @_);

    # If bgcd() is called as a function, the class might be anything.

    return $class -> bgcd(@args) unless $class -> isa(__PACKAGE__);

    # Upgrade if one of the operands are upgraded. This is for cases like
    #
    #   $x = Math::BigInt::Lite::bgcd("1e50");
    #   $gcd = Math::BigInt::Lite::bgcd(5, $x);
    #   $gcd = Math::BigInt::Lite->bgcd(5, $x);

    my $do_upgrade = 0;
    for my $arg (@args) {
        unless ($arg -> isa($class)) {
            $do_upgrade = 1;
            last;
        }
    }
    return $upgrade -> bgcd(@args) if $do_upgrade;

    # Now compute the GCD.

    my ($a, $b, $c);
    $a = shift @args;
    $a = abs($$a);
    while (@args && $a != 1) {
        $b = shift @args;
        next if $$b == 0;
        $b = abs($$b);
        do {
            $c = $a % $b;
            $a = $b;
            $b = $c;
        } while $c;
    }

    return bless \( $a ), $class;
}

sub blcm {

    # Convert calls like Class::method(2) into Class->method(2). It ignores
    # cases like Class::method($x), where $x is an object, because this is
    # indistinguishable from $x->method().

    unless (@_ && (ref($_[0]) || $_[0] =~ /^[a-z]\w*(?:::[a-z]\w*)*$/i)) {
        #carp "Using ", (caller(0))[3], "() as a function is deprecated;",
        #  " use is as a method instead" if warnings::warnif("deprecated");
        unshift @_, __PACKAGE__;
    }

    # Make sure each argument is an object.

    my ($class, @args) = objectify(0, @_);

    my @a = ();
    for my $arg (@args) {
        $arg = $upgrade -> new("$arg")
          unless defined(blessed($arg)) && $arg -> isa($upgrade);
        push @a, $arg;
    }

    $upgrade -> blcm(@a);
}

sub isa {
    # we aren't a BigInt nor BigRat/BigFloat
    $_[1] =~ /^Math::BigInt::Lite/ ? 1 : 0;
}

sub new {
    my ($class, $wanted, @r) = @_;

    return $upgrade->new($wanted) if !defined $wanted;

    # 1e12, NaN, inf, 0x12, 0b11, 1.2e2, "12345678901234567890" etc all upgrade
    if (!ref($wanted)) {
        if ((length($wanted) <= $MAX_NEW_LEN) &&
            ($wanted =~ /^[+-]?[0-9]{1,$MAX_NEW_LEN}(\.0*)?\z/)) {
            my $a = \($wanted+0); # +0 to make a copy and force it numeric
            return bless $a, $class;
        }
        # TODO: 1e10 style constants that are still below MAX_NEW
        if ($wanted =~ /^([+-])?([0-9]+)[eE][+]?([0-9]+)$/) {
            if ((length($2) + $3) < $MAX_NEW_LEN) {
                my $a = \($wanted+0); # +0 to make a copy and force it numeric
                return bless $a, $class;
            }
        }
        #    print "new '$$a' $BASE_LEN ($wanted)\n";
    }
    $upgrade->new($wanted, @r);
}

###############################################################################
# String conversion methods
###############################################################################

sub bstr {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    "$$x";
}

# Scientific notation with significand/mantissa as an integer, e.g., "12345" is
# written as "1.2345e+4".

sub bsstr {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    if ($$x =~ / ^
                 (
                     [+-]?
                     (?: 0 | [1-9] (?: \d* [1-9] )? )
                 )
                 ( 0* )
                 $
               /x)
    {
        my $mant = $1;
        my $expo = CORE::length($2);
        return $mant . "e+" . $expo;
    }

    die "Internal error: ", (caller(0))[3], "() couldn't handle",
      " the value '", $$x, "', which is likely a bug";
}

# Normalized notation, e.g., "12345" is written as "1.2345e+4".

sub bnstr {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    my ($mant, $expo);

    if ($$x =~ / ^
                 (
                     [+-]?
                     \d
                 )
                 ( 0* )
                 $
               /x)
    {
        return $1 . "e+" . CORE::length($2);
    }

    if ($$x =~
        / ^
          ( [+-]? [1-9] )
          (
              ( \d* [1-9] )
              0*
          )
          $
        /x)
    {
        return $1 . "." . $3 . "e+" . CORE::length($2);
    }

    die "Internal error: ", (caller(0))[3], "() couldn't handle",
      " the value '", $$x, "', which is likely a bug";
}

# Engineering notation, e.g., "12345" is written as "12.345e+3".

sub bestr {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    if ($$x =~ / ^
                 ( [+-]? )
                 (
                     0 | [1-9] (?: \d* [1-9] )?
                 )
                 ( 0* )
                 $
               /x)
    {
        my $sign = $1;
        my $mant = $2;
        my $expo = CORE::length($3);
        my $mantlen = CORE::length($mant);          # length of mantissa
        $expo += $mantlen;

        my $dotpos = ($expo - 1) % 3 + 1;           # offset of decimal point
        $expo -= $dotpos;

        if ($dotpos < $mantlen) {
            substr $mant, $dotpos, 0, ".";          # insert decimal point
        } elsif ($dotpos > $mantlen) {
            $mant .= "0" x ($dotpos - $mantlen);    # append zeros
        }

        return ($sign eq '-' ? '-' : '') . $mant . 'e+' . $expo;
    }

    die "Internal error: ", (caller(0))[3], "() couldn't handle",
      " the value '", $$x, "', which is likely a bug";
}

# Decimal notation, e.g., "12345" (no exponent).

sub bdstr {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    "$$x";
}

# Fraction notation, e.g., "123.4375" is written as "1975/16", but "123" is
# written as "123", not "123/1".

sub bfstr {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    "$$x";
}

###############################################################################

sub bnorm {
    # no-op
    my $x = ref($_[0]) ? $_[0] : $_[0]->new($_[1]);

    $x;
}

sub _upgrade_2 {
    # This takes the two possible arguments, and checks them. It uses new() to
    # convert literals to objects first. Then it upgrades the operation
    # when it detects that:
    # * one or both of the argument(s) is/are BigInt,
    # * global A or P are set
    # Input arguments: x, y, a, p, r
    # Output: flag (1: need to upgrade, 0: need not), x, y, $a, $p, $r

    # Math::BigInt::Lite->badd(1, 2) style calls
    shift if !ref($_[0]) && $_[0] =~ /^Math::BigInt::Lite/;

    my ($x, $y, @r) = @_;

    my $up = 0;                 # default: don't upgrade

    $up = 1
      if (defined $r[0] || defined $r[1] || defined $accuracy || defined $precision);
    $x = __PACKAGE__->new($x) unless ref $x; # upgrade literals
    $y = __PACKAGE__->new($y) unless ref $y; # upgrade literals
    $up = 1 unless $x->isa($class) && $y->isa($class);
    # no need to check for overflow for add/sub/div/mod math
    if ($up == 1) {
        $x = $upgrade->new($$x) if $x->isa($class);
        $y = $upgrade->new($$y) if $y->isa($class);
    }

    ($up, $x, $y, @r);
}

sub _upgrade_2_mul {
    # This takes the two possible arguments, and checks them. It uses new() to
    # convert literals to objects first. Then it upgrades the operation
    # when it detects that:
    # * one or both of the argument(s) is/are BigInt,
    # * global A or P are set
    # * One of the arguments is too large for the operation
    # Input arguments: x, y, a, p, r
    # Output: flag (1: need to upgrade, 0: need not), x, y, $a, $p, $r

    # Math::BigInt::Lite->badd(1, 2) style calls
    shift if !ref($_[0]) && $_[0] =~ /^Math::BigInt::Lite/;

    my ($x, $y, @r) = @_;

    my $up = 0;                 # default: don't upgrade

    $up = 1
      if (defined $r[0] || defined $r[1] || defined $accuracy || defined $precision);
    $x = __PACKAGE__->new($x) unless ref $x; # upgrade literals
    $y = __PACKAGE__->new($y) unless ref $y; # upgrade literals
    $up = 1 unless $x->isa($class) && $y->isa($class);
    $up = 1 if ($up == 0 && (abs($$x) >= $MAX_MUL || abs($$y) >= $MAX_MUL) );
    if ($up == 1) {
        $x = $upgrade->new($$x) if $x->isa($class);
        $y = $upgrade->new($$y) if $y->isa($class);
    }
    ($up, $x, $y, @r);
}

sub _upgrade_1 {
    # This takes the one possible argument, and checks it. It uses new() to
    # convert a literal to an object first. Then it checks for a necc. upgrade:
    # * the argument is a BigInt
    # * global A or P are set
    # Input arguments: x, a, p, r
    # Output: flag (1: need to upgrade, 0: need not), x, $a, $p, $r
    my ($x, @r) = @_;

    my $up = 0;                 # default: don't upgrade

    $up = 1
      if (defined $r[0] || defined $r[1] || defined $accuracy || defined $precision);
    $x = __PACKAGE__->new($x) unless ref $x; # upgrade literals
    $up = 1 unless $x->isa($class);
    if ($up == 1) {
        $x = $upgrade->new($$x) if $x->isa($class);
    }
    ($up, $x, @r);
}

##############################################################################
# rounding functions

sub bround {
    my ($class, $x, @a) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    #$m = $self->round_mode() if !defined $m;
    #$a = $self->accuracy() if !defined $a;

    $x = $upgrade->new($$x) if $x->isa($class);
    $x->bround(@a);
}

sub bfround {
    my ($class, $x, @p) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    #$m = $self->round_mode() if !defined $m;
    #$p = $self->precision() if !defined $p;

    $x = $upgrade->new($$x) if $x->isa($class);
    $x->bfround(@p);

}

sub round {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $x->round(@r);
}

##############################################################################
# special values

sub bnan {
    # return a NaN
    shift;
    $upgrade -> bnan(@_);
}

sub binf {
    # return a +/-Inf
    shift;
    $upgrade -> binf(@_);
}

sub bone {
    # return a +/-1
    my $x = shift;

    my ($sign, @r) = @_;

    # Get the sign.

    if (defined($_[0]) && $_[0] =~ /^\s*([+-])\s*$/) {
        $sign = $1;
        shift;
    } else {
        $sign = '+';
    }

    my $num = $sign eq "-" ? -1 : 1;
    return $x -> new($num) unless ref $x;       # $class->bone();
    $$x = $num;
    $x;
}

sub bzero {
    # return a one
    my $x = shift;

    return $x->new(0) unless ref $x;            # $class->bone();
    $$x = 0;
    $x;
}

sub bcmp {
    # compare the value of two objects
    my ($class, $x, $y, @r) = ref($_[0]) && ref($_[0]) eq ref($_[1])
                            ? (ref($_[0]), @_)
                            : objectify(2, @_);

    return $upgrade->bcmp($x, $y)
      if defined($upgrade) && (!$x->isa($class) || !$y->isa($class));

    $$x <=> $$y;
}

sub bacmp {
    # compare the absolute value of two objects
    my ($class, $x, $y, @r) = ref($_[0]) && ref($_[0]) eq ref($_[1])
                            ? (ref($_[0]), @_)
                            : objectify(2, @_);

    return $upgrade->bacmp($x, $y)
      if defined($upgrade) && (!$x->isa($class) || !$y->isa($class));

    abs($$x) <=> abs($$y);
}

##############################################################################
# copy/conversion

sub copy {
    my ($x, $class);
    if (ref($_[0])) {           # $y = $x -> copy()
        $x = shift;
        $class = ref($x);
    } else {                    # $y = $class -> copy($y)
        $class = shift;
        $x = shift;
    }

    my $val = $$x;
    bless \$val, $class;
}

sub as_int {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $x -> copy() if $x -> isa("Math::BigInt");

    # disable upgrading and downgrading

    my $upg = Math::BigInt -> upgrade();
    my $dng = Math::BigInt -> downgrade();
    Math::BigInt -> upgrade(undef);
    Math::BigInt -> downgrade(undef);

    my $y = Math::BigInt -> new($x -> bsstr());

    # reset upgrading and downgrading

    Math::BigInt -> upgrade($upg);
    Math::BigInt -> downgrade($dng);

    return $y;
}

sub as_number {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade->new($x) unless ref($x);
    # as_number needs to return a BigInt
    return $upgrade->new($$x) if $x->isa($class);
    $x->copy();
}

sub numify {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $$x if $x->isa($class);
    $x->numify();
}

sub as_hex {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade->new($$x)->as_hex() if $x->isa($class);
    $x->as_hex();
}

sub as_oct {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade->new($$x)->as_oct() if $x->isa($class);
    $x->as_hex();
}

sub as_bin {
    my ($class, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade->new($$x)->as_bin() if $x->isa($class);
    $x->as_bin();
}

sub from_hex {
    my $self    = shift;
    my $selfref = ref $self;
    my $class   = $selfref || $self;

    my $str = shift;

    # If called as a class method, initialize a new object.

    $self = $class -> bzero() unless $selfref;

    if ($str =~ s/
                     ^
                     \s*
                     ( [+-]? )
                     ( 0? [Xx] )?
                     (
                         [0-9a-fA-F]*
                         ( _ [0-9a-fA-F]+ )*
                     )
                     \s*
                     $
                 //x)
    {
        # Get a "clean" version of the string, i.e., non-emtpy and with no
        # underscores or invalid characters.

        my $sign = $1;
        my $chrs = $3;
        $chrs =~ tr/_//d;
        $chrs = '0' unless CORE::length $chrs;

        return $upgrade -> from_hex($sign . $chrs)
          if length($chrs) > $MAX_HEX_LEN;

        $$self = oct('0x' . $chrs);
        $$self = -$$self if $sign eq '-';

        return $self;
    }

    # For consistency with from_hex() and from_oct(), we return NaN when the
    # input is invalid.

    return $self->bnan();
}

sub from_oct {
    my $self    = shift;
    my $selfref = ref $self;
    my $class   = $selfref || $self;

    my $str = shift;

    # If called as a class method, initialize a new object.

    $self = $class -> bzero() unless $selfref;

    if ($str =~ s/
                     ^
                     \s*
                     ( [+-]? )
                     ( 0? [Oo] )?
                     (
                         [0-7]*
                         ( _ [0-7]+ )*
                     )
                     \s*
                     $
                 //x)
    {
        # Get a "clean" version of the string, i.e., non-emtpy and with no
        # underscores or invalid characters.

        my $sign = $1;
        my $chrs = $3;
        $chrs =~ tr/_//d;
        $chrs = '0' unless CORE::length $chrs;

        return $upgrade -> from_oct($sign . $chrs)
          if length($chrs) > $MAX_OCT_LEN;

        $$self = oct($chrs);
        $$self = -$$self if $sign eq '-';

        return $self;
    }

    # For consistency with from_hex() and from_oct(), we return NaN when the
    # input is invalid.

    return $self->bnan();
}

sub from_bin {
    my $self    = shift;
    my $selfref = ref $self;
    my $class   = $selfref || $self;

    my $str = shift;

    # If called as a class method, initialize a new object.

    $self = $class -> bzero() unless $selfref;

    if ($str =~ s/
                     ^
                     \s*
                     ( [+-]? )
                     ( 0? [Bb] )?
                     (
                         [01]*
                         ( _ [01]+ )*
                     )
                     \s*
                     $
                 //x)
    {
        # Get a "clean" version of the string, i.e., non-emtpy and with no
        # underscores or invalid characters.

        my $sign = $1;
        my $chrs = $3;
        $chrs =~ tr/_//d;
        $chrs = '0' unless CORE::length $chrs;

        return $upgrade -> from_bin($sign . $chrs)
          if length($chrs) > $MAX_BIN_LEN;

        $$self = oct('0b' . $chrs);
        $$self = -$$self if $sign eq '-';

        return $self;
    }

    # For consistency with from_hex() and from_oct(), we return NaN when the
    # input is invalid.

    return $self->bnan();
}

##############################################################################
# binc/bdec

sub binc {
    # increment by one
    my ($up, $x, $y, @r) = _upgrade_1(@_);

    return $x->binc(@r) if $up;
    $$x++;
    return $upgrade->new($$x) if abs($$x) > $MAX_ADD;
    $x;
}

sub bdec {
    # decrement by one
    my ($up, $x, $y, @r) = _upgrade_1(@_);

    return $x->bdec(@r) if $up;
    $$x--;
    return $upgrade->new($$x) if abs($$x) > $MAX_ADD;
    $x;
}

##############################################################################
# shifting

sub brsft {
    # shift right
    my ($class, $x, $y, $b, @r) = objectify(2, @_);

    $x = $class->new($x) unless ref($x);
    $y = $class->new($y) unless ref($y);
    $b = $$b if ref $b && $b->isa($class);

    if (!$x->isa($class)) {
        $y = $upgrade->new($$y) if $y->isa($class);
        return $x->brsft($y, $b, @r);
    }
    return $upgrade->new($$x)->brsft($y, $b, @r)
      unless $y->isa($class);

    $b = 2 if !defined $b;
    # can't do this
    return $upgrade->new($$x)->brsft($upgrade->new($$y), $b, @r)
      if $b != 2 || $$y < 0;
    use integer;
    $$x >>= $$y;                # only base 2 for now
    $x;
}

sub blsft {
    # shift left
    my ($class, $x, $y, $b, @r) = objectify(2, @_);

    $x = $class->new($x) unless ref($x);
    $y = $class->new($x) unless ref($y);

    return $x->blsft($upgrade->new($$y), $b, @r) unless $x->isa($class);
    return $upgrade->new($$x)->blsft($y, $b, @r)
      unless $y->isa($class);

    # overflow: can't do this
    return $upgrade->new($$x)->blsft($upgrade->new($$y), $b, @r)
      if $$y > 31;
    $b = 2 if !defined $b;
    # can't do this
    return $upgrade->new($$x)->blsft($upgrade->new($$y), $b, @r)
      if $b != 2 || $$y < 0;
    use integer;
    $$x <<= $$y;                # only base 2 for now
    $x;
}

###############################################################################
# Bitwise methods
###############################################################################

# Bitwise left shift.

sub bblsft {
    my ($class, $x, $y, @r) = ref($_[0]) ? (ref($_[0]), @_) : @_;
    # For now, upgrade, but we should handle simple cases here. Fixme!
    $upgrade -> bblsft($x, $y, @r);
}

# Bitwise right shift.

sub bbrsft {
    my ($class, $x, $y, @r) = ref($_[0]) ? (ref($_[0]), @_) : @_;
    # For now, upgrade, but we should handle simple cases here. Fixme!
    $upgrade -> bbrsft($x, $y, @r);
}

sub band {
    # AND two objects
    my ($class, $x, $y, @r) = ref($_[0]) && ref($_[0]) eq ref($_[1])
                            ? (ref($_[0]), @_) : objectify(2, @_);

    return $upgrade -> band($x, $y, @r)
      unless $x -> isa($class) && $y -> isa($class);

    use integer;
    $$x = ($$x+0) & ($$y+0);    # +0 to avoid string-context
    $x;
}

sub bxor {
    # XOR two objects
    my ($class, $x, $y, @r) = ref($_[0]) && ref($_[0]) eq ref($_[1])
                            ? (ref($_[0]), @_) : objectify(2, @_);

    return $upgrade -> bxor($x, $y, @r)
      unless $x -> isa($class) && $y -> isa($class);

    use integer;
    $$x = ($$x+0) ^ ($$y+0);    # +0 to avoid string-context
    $x;
}

sub bior {
    # OR two objects
    my ($class, $x, $y, @r) = ref($_[0]) && ref($_[0]) eq ref($_[1])
                            ? (ref($_[0]), @_) : objectify(2, @_);

    return $upgrade -> bior($x, $y, @r)
      unless $x -> isa($class) && $y -> isa($class);

    use integer;
    $$x = ($$x+0) | ($$y+0);    # +0 to avoid string-context
    $x;
}

##############################################################################
# mul/add/div etc

sub badd {
    # add two objects
    my ($up, $x, $y, @r) = _upgrade_2(@_);

    return $x->badd($y, @r) if $up;

    $$x = $$x + $$y;
    return $upgrade->new($$x) if abs($$x) > $MAX_ADD;
    $x;
}

sub bsub {
    # subtract two objects
    my ($up, $x, $y, @r) = _upgrade_2(@_);
    return $x->bsub($y, @r) if $up;
    $$x = $$x - $$y;
    return $upgrade->new($$x) if abs($$x) > $MAX_ADD;
    $x;
}

sub bmul {
    # multiply two objects
    my ($up, $x, $y, @r) = _upgrade_2_mul(@_);
    return $x->bmul($y, @r) if $up;
    $$x = $$x * $$y;
    $$x = 0 if $$x eq '-0';  # for some Perls leave '-0' here
    #return $upgrade->new($$x) if abs($$x) > $MAX_ADD;
    $x;
}

sub bmod {
    # remainder of div
    my ($up, $x, $y, @r) = _upgrade_2(@_);
    return $x->bmod($y, @r) if $up;
    return $upgrade->new($$x)->bmod($y, @r) if $$y == 0;
    $$x = $$x % $$y;
    $x;
}

sub bdiv {
    # divide two objects
    my ($up, $x, $y, @r) = _upgrade_2(@_);

    return $x->bdiv($y, @r) if $up;

    return $upgrade->new($$x)->bdiv($$y, @r) if $$y == 0;

    # need to give Math::BigInt a chance to upgrade further
    return $upgrade->new($$x)->bdiv($$y, @r)
      if defined $Math::BigInt::upgrade;

    my ($quo, $rem);

    $rem = \($$x % $$y);
    $quo = int($$x / $$y);
    $quo-- if $$rem != 0 && ($$x <=> 0) != ($$y <=> 0);

    $$x = $quo;

    if (wantarray) {
        bless $rem, $class;
        return $x, $rem;
    }

    return $x;
}

sub btdiv {
    # divide two objects
    my ($up, $x, $y, @r) = _upgrade_2(@_);

    return $x->btdiv($y, @r) if $up;

    return $upgrade->new($$x)->btdiv($$y, @r) if $$y == 0;

    # need to give Math::BigInt a chance to upgrade further
    return $upgrade->new($$x)->btdiv($$y, @r)
      if defined $Math::BigInt::upgrade;

    my ($quo, $rem);

    if (wantarray) {
        $rem = \($$x % $$y);
        $$rem -= $$y if $$rem != 0 && ($$x <=> 0) != ($$y <=> 0);
        bless $rem, $class;
    }

    $quo = int($$x / $$y);

    $$x = $quo;
    return $x, $rem if wantarray;
    return $x;
}

##############################################################################
# is_foo methods (the rest is inherited)

sub is_int {
    # return true if arg (BLite or num_str) is an integer
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return 1 if $x->isa($class); # Lite objects are always int
    $x->is_int();
}

sub is_inf {
    # return true if arg (BLite or num_str) is an infinity
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return 0 if $x->isa($class); # Lite objects are never inf
    $x->is_inf();
}

sub is_nan {
    # return true if arg (BLite or num_str) is an NaN
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return 0 if $x->isa($class); # Lite objects are never NaN
    $x->is_nan();
}

sub is_zero {
    # return true if arg (BLite or num_str) is zero
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return ($$x == 0) <=> 0 if $x->isa($class);
    $x->is_zero();
}

sub is_positive {
    # return true if arg (BLite or num_str) is positive
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return ($$x > 0) <=> 0 if $x->isa($class);
    $x->is_positive();
}

sub is_negative {
    # return true if arg (BLite or num_str) is negative
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return ($$x < 0) <=> 0 if $x->isa($class);
    $x->is_positive();
}

sub is_one {
    # return true if arg (BLite or num_str) is one
    my ($class, $x, $s) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    my $one = 1;
    $one = -1 if ($s || '+') eq '-';
    return ($$x == $one) <=> 0 if $x->isa($class);
    $x->is_one();
}

sub is_odd {
    # return true if arg (BLite or num_str) is odd
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $x->is_odd() unless $x->isa($class);
    $$x & 1 == 1 ? 1 : 0;
}

sub is_even {
    # return true if arg (BLite or num_str) is even
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $x->is_even() unless $x->isa($class);
    $$x & 1 == 1 ? 0 : 1;
}

##############################################################################
# parts() and friends

sub sign {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    $$x >= 0 ? '+' : '-';
}

sub parts {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    if ($$x =~ / ^
                 (
                     [+-]?
                     (?: 0 | [1-9] (?: \d* [1-9] )? )
                 )
                 ( 0* )
                 $
               /x)
    {
        my $mant = $1;
        my $expo = CORE::length($2);
        return $class -> new($mant), $class -> new($expo);
    }

    die "Internal error: ", (caller(0))[3], "() couldn't handle",
      " the value '", $$x, "', which is likely a bug";
}

sub exponent {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    my $expo;
    if ($$x =~ / (?: ^ 0 | [1-9] ) ( 0* ) $/x) {
        $expo = CORE::length($1);
        return $class -> new($expo);
    }

    die "Internal error: ", (caller(0))[3], "() couldn't handle",
      " the value '", $$x, "', which is likely a bug";
}

sub mantissa {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    if ($$x =~ / ^
                 (
                     [+-]?
                     (?: 0 | [1-9] (?: \d* [1-9] )? )
                 )
               /x)
    {
        return $class -> new($1);
    }

    die "Internal error: ", (caller(0))[3], "() couldn't handle",
      " the value '", $$x, "', which is likely a bug";
}

sub sparts {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    if ($$x =~ / ^
                 (
                     [+-]?
                     (?: 0 | [1-9] (?: \d* [1-9] )? )
                 )
                 ( 0* )
                 $
               /x)
    {
        my $mant = $1;
        my $expo = CORE::length($2);
        return $class -> new($mant) unless wantarray;
        return $class -> new($mant), $class -> new($expo);
    }

    die "Internal error: ", (caller(0))[3], "() couldn't handle",
      " the value '", $$x, "', which is likely a bug";
}

sub nparts {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    my ($mant, $expo);
    if ($$x =~ / ^
                 ( [+-]? \d )
                 ( 0* )
                 $
               /x)
    {
        $mant = $class -> new($1);
        $expo = $class -> new(CORE::length($2));
    } elsif ($$x =~
             / ^
               ( [+-]? [1-9] )
               ( \d+ )
               $
             /x)
    {
        $mant = $upgrade -> new($1 . "." . $2);
        $expo = $class -> new(CORE::length($2));
    } else {
        die "Internal error: ", (caller(0))[3], "() couldn't handle",
          " the value '", $$x, "', which is likely a bug";
    }

    return $mant unless wantarray;
    return $mant, $expo;
}

sub eparts {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    # Finite number.

    my ($mant, $expo) = $x -> sparts();

    if ($mant -> bcmp(0)) {
        my $ndigmant  = $mant -> length();
        $expo = $expo -> badd($ndigmant);

        # $c is the number of digits that will be in the integer part of the
        # final mantissa.

        my $c = $expo -> copy() -> bdec() -> bmod(3) -> binc();
        $expo = $expo -> bsub($c);

        if ($ndigmant > $c) {
            return $upgrade -> eparts($x) if defined $upgrade;
            $mant = $mant -> bnan();
            return $mant unless wantarray;
            return ($mant, $expo);
        }

        $mant = $mant -> blsft($c - $ndigmant, 10);
    }

    return $mant unless wantarray;
    return ($mant, $expo);
}

sub dparts {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    my $int = $x -> copy();
    my $frc = $class -> bzero();
    return $int unless wantarray;
    return $int, $frc;
}

sub fparts {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $upgrade -> exponent($x)
      if defined($upgrade) && !$x -> isa($class);

    my $num = $x -> copy();
    my $den = $class -> bone();
    return $num unless wantarray;
    return $num, $den;
}

sub digit {
    my ($class, $x, $n) = ref($_[0]) ? (ref($_[0]), @_) : objectify(1, @_);

    return $x->digit($n) unless $x->isa($class);

    $n = 0 if !defined $n;
    my $len = length("$$x");

    $n = $len+$n if $n < 0;     # -1 last, -2 second-to-last
    $n = abs($n);               # if negative was too big
    $len--;
    $n = $len if $n > $len;     # n to big?

    substr($$x, -$n-1, 1);
}

sub length {
    my ($class, $x) = ref($_[0]) ? (ref($_[0]), $_[0]) : objectify(1, @_);

    return $x->length() unless $x->isa($class);
    my $l = length($$x);
    $l-- if $$x < 0;            # -123 => 123
    $l;
}

##############################################################################
# sign based methods

sub babs {
    my ($class, $x) = ref($_[0]) ? (undef, $_[0]) : objectify(1, @_);

    $$x = abs($$x);
    $x;
}

sub bneg {
    my ($class, $x) = ref($_[0]) ? (undef, $_[0]) : objectify(1, @_);

    $$x = -$$x if $$x != 0;
    $x;
}

sub bnot {
    my ($class, $x) = ref($_[0]) ? (undef, $_[0]) : objectify(1, @_);

    $$x = -$$x - 1;
    $x;
}

##############################################################################
# special calc routines

sub bceil {
    my ($class, $x) = ref($_[0]) ? (undef, $_[0]) : objectify(1, @_);
    $x;                         # no-op
}

sub bfloor {
    my ($class, $x) = ref($_[0]) ? (undef, $_[0]) : objectify(1, @_);
    $x;                         # no-op
}

sub bint {
    my ($class, $x) = ref($_[0]) ? (undef, $_[0]) : objectify(1, @_);
    $x;                         # no-op
}

sub bfac {
    my ($self, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) :
      ($class, $class->new($_[0]), $_[1], $_[2], $_[3], $_[4]);

    $x = $upgrade->new($$x) if $x->isa($class);
    $upgrade->bfac($x, @r);
}

sub bdfac {
    my ($self, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) :
      ($class, $class->new($_[0]), $_[1], $_[2], $_[3], $_[4]);

    $x = $upgrade->new($$x) if $x->isa($class);
    $upgrade->bdfac($x, @r);
}

sub btfac {
    my ($self, $x, @r) = ref($_[0]) ? (ref($_[0]), @_) :
      ($class, $class->new($_[0]), $_[1], $_[2], $_[3], $_[4]);

    $x = $upgrade->new($$x) if $x->isa($class);
    $upgrade->btfac($x, @r);
}

sub bmfac {
    my ($class, $x, $k, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $upgrade->bmfac($x, $k, @r);
}

sub bpow {
    my ($class, $x, $y, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $y = $upgrade->new($$y) if $y->isa($class);

    $x->bpow($y, @r);
}

sub blog {
    my ($class, $x, $base, @r);

    # Don't objectify the base, since an undefined base, as in $x->blog() or
    # $x->blog(undef) signals that the base is Euler's number.

    if (!ref($_[0]) && $_[0] =~ /^[A-Za-z]|::/) {
        # E.g., Math::BigInt::Lite->blog(256, 2)
        ($class, $x, $base, @r) =
          defined $_[2] ? objectify(2, @_) : objectify(1, @_);
    } else {
        # E.g., Math::BigInt::Lite::blog(256, 2) or $x->blog(2)
        ($class, $x, $base, @r) =
          defined $_[1] ? objectify(2, @_) : objectify(1, @_);
    }

    $x = $upgrade->new($$x) if $x->isa($class);
    $base = $upgrade->new($$base) if defined $base && $base->isa($class);

    $x->blog($base, @r);
}

sub bexp {
    my ($class, $x, @r) = objectify(1, @_);

    $x = $upgrade->new($$x) if $x->isa($class);

    $x->bexp(@r);
}

sub batan2 {
    my ($class, $x, $y, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);

    $x->batan2($y, @r);
}

sub bnok {
    my ($class, $x, $y, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $y = $upgrade->new($$y) if $y->isa($class);

    $x->bnok($y, @r);
}

sub broot {
    my ($class, $x, $base, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $base = $upgrade->new($$base) if defined $base && $base->isa($class);

    $x->broot($base, @r);
}

sub bmuladd {
    my ($class, $x, $y, $z, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $y = $upgrade->new($$y) if defined $y && $y->isa($class);
    $z = $upgrade->new($$z) if defined $z && $z->isa($class);

    $x->bmuladd($y, $z, @r);
}

sub bmodpow {
    my ($class, $x, $y, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $y = $upgrade->new($$y) if defined $y && $y->isa($class);

    $x->bmodpow($y, @r);
}

sub bmodinv {
    my ($class, $x, $y, @r) = objectify(2, @_);

    $x = $upgrade->new($$x) if $x->isa($class);
    $y = $upgrade->new($$y) if defined $y && $y->isa($class);

    $x->bmodinv($y, @r);
}

sub bsqrt {
    my ($class, $x, @r) =
      ref($_[0]) ? (ref($_[0]), @_)
                 : ($class, $class->new($_[0]), $_[1], $_[2], $_[3]);

    return $x->bsqrt(@r) unless $x->isa($class);

    return $upgrade->new($$x)->bsqrt() if $$x < 0; # NaN
    my $s = sqrt($$x);
    # If MBI's upgrade is defined, and result is non-integer, we need to hand
    # up. If upgrade is undef, result would be the same, anyway
    if (int($s) != $s) {
        return $upgrade->new($$x)->bsqrt();
    }
    $$x = $s;
    $x;
}

sub bpi {
    my $self = shift;
    my $class = ref($self) || $self;
    $class -> new("3");
}

sub to_bin {
    my $self  = shift;
    $upgrade -> new($$self) -> to_bin();
}

sub to_oct {
    my $self  = shift;
    $upgrade -> new($$self) -> to_oct();
}

sub to_hex {
    my $self  = shift;
    $upgrade -> new($$self) -> to_hex();
}

##############################################################################

sub import {
    my $self = shift;

    my @a = @_;
    my $l = scalar @_;
    my $j = 0;
    my $lib = '';
    for (my $i = 0; $i < $l ; $i++, $j++) {
        if ($_[$i] eq ':constant') {
            # this causes overlord er load to step in
            overload::constant integer => sub { $self->new(shift) };
            splice @a, $j, 1;
            $j --;
        } elsif ($_[$i] eq 'upgrade') {
            # this causes upgrading
            $upgrade = $_[$i+1]; # or undef to disable
            my $s = 2;
            $s = 1 if @a-$j < 2; # no "can not modify non-existant..."
            splice @a, $j, $s;
            $j -= $s;
        } elsif ($_[$i] eq 'lib') {
            $lib = $_[$i+1];    # or undef to disable
            my $s = 2;
            $s = 1 if @a-$j < 2; # no "can not modify non-existant..."
            splice @a, $j, $s;
            $j -= $s;
        }
    }
    # any non :constant stuff is handled by our parent,
    # even if @_ is empty, to give it a chance
    $self->SUPER::import(@a);           # need it for subclasses
    $self->export_to_level(1, $self, @a); # need it for MBF
}

1;

__END__