Persistent::DataType::Number - A Floating Point and Integer Class

Persistent-Base documentation Contained in the Persistent-Base distribution.

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NAME

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Persistent::DataType::Number - A Floating Point and Integer Class

SYNOPSIS

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  use Persistent::DataType::Number;
  use English;

  eval {  ### in case an exception is thrown ###

    ### allocate a number ###
    my $number = new Persistent::DataType::Number($value,
                                                  $precision,
						  $scale);

    ### get/set value of number ###
    $value = $number->value($new_value);

    ### get/set precision of the number ###
    $precision = $number->precision($new_precision);

    ### get/set scale of number ###
    $scale = $number->scale($new_scale);

    ### returns '<=>' for numbers ###
    my $cmp_op = $number->get_compare_op();
  };

  if ($EVAL_ERROR) {  ### catch those exceptions! ###
    print "An error occurred: $EVAL_ERROR\n";
  }

ABSTRACT

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This is a floating point and integer class used by the Persistent framework of classes to implement the attributes of objects. This class provides methods for accessing the value, precision, scale, and comparison operator of a number.

This class is usually not invoked directly, at least not when used with the Persistent framework of classes. However, the constructor arguments of this class are usually of interest when defining the attributes of a Persistent object since the add_attribute method of the Persistent classes instantiates this class directly. Also, the arguments to the value method are of interest when dealing with the accessor methods of the Persistent classes since the accessor methods pass their arguments to the value method and return the string value from the value method.

This class is part of the Persistent base package which is available from:

  http://www.bigsnow.org/persistent
  ftp://ftp.bigsnow.org/pub/persistent

DESCRIPTION

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Before we get started describing the methods in detail, it should be noted that all error handling in this class is done with exceptions. So you should wrap an eval block around all of your code. Please see the Persistent documentation for more information on exception handling in Perl.

METHODS

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Constructor -- Creates the Number Object

  eval {
    my $number = new Persistent::DataType::Number($value,
                                                  $precision,
                                                  $scale);
  };
  croak "Exception caught: $@" if $@;

Initializes a number object. This method throws Perl execeptions so use it with an eval block.

Parameters:

$value

Actual value of the number; this may be a floating point or integer. This argument is optional and may be set to undef.

$precision

The number of digits in the number not including the decimal point or the sign. This argument is optional and will be initialized to the precision of the $value argument as a default.

$scale

The number of digits after the decimal point. This argument is optional and will be initialized to the scale of the $value argument as a default.

value -- Accesses the Value of the Number

  eval {
    ### set the value ###
    $number->value($value);

    ### get the value ###
    $value = $number->value();
  };
  croak "Exception caught: $@" if $@;

Sets the value of the number and/or returns the value. This method throws Perl execeptions so use it with an eval block.

Parameters:

$value

Actual value of the number; this may be a floating point or integer. This argument is optional and may be set to undef.

get_compare_op -- Returns the Comparison Operator

  $cmp_op = $number->get_compare_op();

Returns the comparison operator for the Number class which is '<=>'. This method does not throw execeptions.

Parameters:

None

precision -- Accesses the Precision of the Number

  eval {
    ### set the precision ###
    $number->precision($new_precision);

    ### get the precision ###
    $precision = $number->precision();
  };
  croak "Exception caught: $@" if $@;

Sets the precision of the number and/or returns it. This method throws Perl execeptions so use it with an eval block.

Parameters:

$precision

The number of digits in the number not including the decimal point or the sign. The precision must be >= 0. If it is undef or the empty string (''), then it is set to 0.

scale -- Accesses the Scale of the Number

  eval {
    ### set the scale ###
    $number->scale($new_scale);

    ### get the scale ###
    $scale = $number->scale();
  };
  croak "Exception caught: $@" if $@;

Sets the scale of the number and/or returns it. This method throws Perl execeptions so use it with an eval block.

Parameters:

$scale

The number of digits after the decimal point. The scale must be >= 0. If it is undef or the empty string (''), then it is set to 0.

SEE ALSO

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Persistent, Persistent::DataType::Char, Persistent::DataType::DateTime, Persistent::DataType::String, Persistent::DataType::VarChar

BUGS

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This software is definitely a work in progress. So if you find any bugs please email them to me with a subject of 'Persistent Bug' at:

  winters@bigsnow.org

And you know, include the regular stuff, OS, Perl version, snippet of code, etc.

AUTHORS

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  David Winters <winters@bigsnow.org>

COPYRIGHT

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Copyright (c) 1998-2000 David Winters. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

Persistent-Base documentation Contained in the Persistent-Base distribution. 
########################################################################
# File:     Number.pm
# Author:   David Winters <winters@bigsnow.org>
# RCS:      $Id: Number.pm,v 1.6 2000/02/08 02:36:40 winters Exp winters $
#
# A floating point and integer class.
#
# This file contains POD documentation that may be viewed with the
# perldoc, pod2man, or pod2html utilities.
#
# Copyright (c) 1998-2000 David Winters.  All rights reserved.
# This program is free software; you can redistribute it
# and/or modify it under the same terms as Perl itself.
########################################################################

package Persistent::DataType::Number;
require 5.004;

use strict;
use vars qw($VERSION $REVISION @ISA);

### we are a subclass of the all-powerful Persistent::DataType::Base class ###
use Persistent::DataType::Base;
@ISA = qw(Persistent::DataType::Base);

use Carp;

### copy version number from superclass ###
$VERSION = $Persistent::DataType::Base::VERSION;
$REVISION = (qw$Revision: 1.6 $)[1];


########################################################################
#
# --------------------------------------------------------------------
# PUBLIC ABSTRACT METHODS OVERRIDDEN (REDEFINED) FROM THE PARENT CLASS
# --------------------------------------------------------------------
#
########################################################################

########################################################################
# initialize
########################################################################


sub initialize {
  my($this, $value, $precision, $scale) = @_;

  $this->_trace();

  ### parse out the digits before and after the decimal point ###
  my($before, $after) = _parse_number($value);

  ### set the attributes ###
  $precision = length($before) + length($after) if !defined($precision);
  $this->precision($precision);
  $scale = length($after) if !defined($scale);
  $this->scale($scale);
  $this->value($value);
}

########################################################################
# value
########################################################################


sub value {
  (@_ == 1 || @_ == 2) or croak 'Usage: $obj->value([$value])';
  my $this = shift;
  ref($this) or croak "$this is not an object";

  $this->_trace();

  ### set the value ###
  if (@_) {
    my $value = shift;
    $value = undef if defined $value && $value eq '';

    ### parse out the digits before and after the decimal point ###
    my($before, $after) = _parse_number($value);

    ### get the precision and scale of the object ###
    my $precision = $this->precision();
    my $scale = $this->scale();

    ### check the length ###
    if (length($before) + length($after) > $precision) {
      croak "'$value' is longer than $precision digit(s) of precision";
    } elsif (length($after) > $scale) {
      croak "'$value' is longer than $scale digit(s) of scale";
    } else {
      $value = $value + 0 if defined $value;  ### force numeric context ###
      $this->{Data}->{Value} = $value;
    }
  }

  ### return the value ###
  $this->{Data}->{Value};
}

########################################################################
# get_compare_op
########################################################################


sub get_compare_op {
  (@_ == 1) or croak 'Usage: $obj->get_compare_op()';
  my $this = shift;
  ref($this) or croak "$this is not an object";

  $this->_trace();

  '<=>';  ### number comparison operator ###
}

########################################################################
#
# --------------
# PUBLIC METHODS
# --------------
#
########################################################################

########################################################################
# precision
########################################################################


sub precision {
  (@_ == 1 || @_ == 2) or croak 'Usage: $obj->precision([$precision])';
  my $this = shift;
  ref($this) or croak "$this is not an object";

  $this->_trace();

  ### set the precision ###
  if (@_) {
    my $precision = shift;
    $precision = 0 if !defined($precision) || $precision eq '';
    croak "precision ($precision) must be >= 0" if $precision < 0;
    $this->{Data}->{Precision} = $precision;

    ### check that the value is not too long ###
    my $value = $this->value();
    if (defined $value) {
      $value =~ s/[\-\.]//g;
      if (length($value) > $precision) {
	croak(sprint("'%s' is longer than $precision digit(s) of precision",
		     $this->value()));
      }
    }
  }

  ### return the precision ###
  $this->{Data}->{Precision};
}

########################################################################
# scale
########################################################################


sub scale {
  (@_ == 1 || @_ == 2) or croak 'Usage: $obj->scale([$scale])';
  my $this = shift;
  ref($this) or croak "$this is not an object";

  $this->_trace();

  ### set the scale ###
  if (@_) {
    my $scale = shift;
    $scale = 0 if !defined($scale) || $scale eq '';
    croak "scale ($scale) must be >= 0" if $scale < 0;
    $this->{Data}->{Scale} = $scale;

    ### check that the value is not too long ###
    my $value = $this->value();
    if (defined $value) {
      if ($value =~ /^\d*\.(\d*)$/) {
	if (length($1) > $scale) {
	  croak(sprint("'%s' is longer than $scale digit(s) of scale",
		       $this->value()));
	}
      }
    }
  }

  ### return the scale ###
  $this->{Data}->{Scale};
}

########################################################################
#
# ---------------
# PRIVATE METHODS
# ---------------
#
# NOTE: These methods do not need to be overridden in the subclasses.
#       However, you may certainly override these methods if you see
#       the need to.
#
########################################################################

########################################################################
# Function:    _parse_number
# Description: Parses the number into digits before and after the
#              decimal point.  Insignificant trailing zeroes will be
#              truncated.
# Parameters:  None
# Returns:     None
########################################################################
sub _parse_number {
  my $value = shift;

  my $before = '';
  my $after = '';

  if (defined $value) {
    if ($value =~ /^[+-]?(\d*)\.?(\d*)$/) {
      $before = $1;  $after = $2;
      $after =~ s/0+$//;  ### remove trailing zeroes ###
    } else {
      croak "'$value' is not a number";
    }
  }

  ($before, $after);
}

### end of library ###
1;
__END__