程嶏清单14-21.txt

< linux网络编程工具>>配套源码

package FixNum;
use strict;
my $PLACES = 0;
sub new {
    my $proto   = shift;
    my $class   = ref($proto) || $proto;
    my $parent  = ref($proto) && $proto;
    my $v = shift;
    my $self = {
        VALUE  => $v,
        PLACES => undef,
    }; 
    if ($parent && defined $parent->{PLACES}) {
        $self->{PLACES} = $parent->{PLACES};
    } elsif ($v =~ /(\.\d*)/) {
        $self->{PLACES} = length($1) - 1;
    }  else {
        $self->{PLACES} = 0;
    } 
    return bless $self, $class;
} 
sub places {
    my $proto = shift;
    my $self  = ref($proto) && $proto;
    my $type  = ref($proto) || $proto;
    if (@_) {
        my $places = shift;
        ($self ? $self->{PLACES} : $PLACES) = $places;
    } 
    return $self ? $self->{PLACES} : $PLACES;
} 
sub _max { $_[0] > $_[1] ? $_[0] : $_[1] } 
use overload '+'    => \&add,
             '*'    => \&multiply,
             '/'    => \&divide,
             '<=>'  => \&spaceship,
             '""'   => \&as_string,
             '0+'   => \&as_number;
sub add {
    my ($this, $that, $flipped) = @_;
    my $result = $this->new( $this->{VALUE} + $that->{VALUE} );
    $result->places( _max($this->{PLACES}, $that->{PLACES} ));
    return $result;
} 
sub multiply {
    my ($this, $that, $flipped) = @_;
    my $result = $this->new( $this->{VALUE} * $that->{VALUE} );
    $result->places( _max($this->{PLACES}, $that->{PLACES} ));
    return $result;
} 
sub divide {
    my ($this, $that, $flipped) = @_;
    my $result = $this->new( $this->{VALUE} / $that->{VALUE} );
    $result->places( _max($this->{PLACES}, $that->{PLACES} ));
    return $result;
} 
sub as_string {
    my $self = shift;
    return sprintf("STR%s: %.*f", ref($self), 
        defined($self->{PLACES}) ? $self->{PLACES} : $PLACES,
            $self->{VALUE}); 
} 
sub as_number {
    my $self = shift;
    return $self->{VALUE};
} 
sub spaceship {
    my ($this, $that, $flipped) = @_;
    $this->{VALUE} <=> $that->{VALUE};
} 
1;