use strict;
use warnings;
use diagnostics;

use Tk 800;
use Tk::Entry;
use Tk::Button;
use Tk::DialogBox;

my $calc    = '0.00';
my $r       = 0;
my $w       = '0';
my $h       = 1;
my $buffer  = '';
my $dbuffer = '';
my %button;
my @rows;


my $mw = new MainWindow(-title => 'Calc');
$mw->geometry("300x300");


my $menubar = $mw->Menu;
$mw->configure(-menu => menuconf());

my $topframe = $mw->Frame(-height => '60', -width => '300')->pack(-sid
+e => 'top', -expand => '0', -fill => 'x');
my $btmframe = $mw->Frame(-height => '225', -width => '300',)->pack(-s
+ide => 'left', -expand => '1', -fill => 'both');
push @rows, $btmframe->Frame()->pack( -expand => 1, -fill => 'both', -
+side => 'top') for (0..3);

my $display   =  $topframe->Entry(-justify      => 'right',
                                  -state        => 'disabled', 
                                  -textvariable => \$calc)
                           ->pack(-expand       => '1',
                                  -fill         => 'x',
                                  -pady         => 30,
                                  -padx         => 20,
                                  -side         => 'right');

$mw->bind("<KeyRelease>" , sub { &keypress } );


for my $i (
qw/
   7 8 9 * n*
   4 5 6 - \/
   1 2 3 + =
   0 . C     / )
{

if($i eq '+' || $i eq '=')
{
$h = 3;
}


$button{$i} = $rows[$r]->Button(-text    => "$i", 
                                -width   => '3', 
                                -height  => "$h", 
                                -command => sub { &btnpress($i) })
                         ->pack(-expand  => 1,
                                -fill    => 'both',
                                -padx    => 2, 
                                -pady    => 2,
                                -side    => 'left',
                                -ipadx   => 5, 
                                -ipady   => 5);

$w++;
$h = 1;

if($w > 4){$w = 0; $r++;}
}



MainLoop;


sub btnpress{
my $btn = shift;

if($btn eq 'n*' && $buffer ne '')
{
   $btn = '**';
   calc($btn);
}

elsif($btn eq 'C')
{
   $calc   = '0.00';
   $buffer = '';
   $dbuffer= '';
}

elsif($btn eq '=')
{
   $buffer = eval($buffer);
   $calc = sprintf "%0.2f", $buffer;
}

else
{  
   calc($btn);
}
}

sub calc{

 my $btn = shift;
 $buffer = $buffer . $btn;

 if( $btn =~ /(\d)|\./){ $dbuffer = $dbuffer . $btn }

 unless( $btn =~ /(\d)|\./){ $calc = ''; $dbuffer = ''; }
 
 if( $btn =~ /(\d)|\./){ $calc = sprintf "%0.2f", $dbuffer; }
}


sub keypress{

 if($_[0] ne 'q'){
 my $widget = shift;
 my $e = $widget->XEvent;    # get event object
 my $btn = $e->K;
 $btn=~s/period/\./ig;

 if( $btn =~/c/ig ){ $btn = uc $btn; $button{$btn}->invoke; }
 if( $btn =~/q/ig ){ exit 0; }    
 if( $btn =~/(\d)|\./){ &btnpress($btn); }
}
else
{
exit 0;
}
}

sub menuconf{

 my $file_menu = $menubar->cascade(-label => "~File");
 my $func_menu = $menubar->cascade(-label => "~Function");
 my $help_menu = $menubar->cascade(-label => "~Help");

 $file_menu->command(-label => "~Clear     C",     -command => sub { \
+&btnpress('C' );  });
 $file_menu->command(-label => "~Exit      Q",     -command => sub { \
+&keypress('q' );  });
 $func_menu->command(-label => "~Add       +" ,    -command => sub { \
+&btnpress('+' );  });
 $func_menu->command(-label => "~Minus     -" ,    -command => sub { \
+&btnpress('-' );  });
 $func_menu->command(-label => "~Multiply  x" ,    -command => sub { \
+&btnpress('x' );  });
 $func_menu->command(-label => "~Divide    /" ,    -command => sub { \
+&btnpress('/' );  });
 $func_menu->command(-label => "~Power of  n*",    -command => sub { \
+&btnpress('n*');  });
 $func_menu->command(-label => "~Equals    =" ,    -command => sub { \
+&btnpress('=' );  });
 $help_menu->command(-label => "~About"       ,    -command => sub { \
+&aboutbox()       });

return $menubar;
}

sub aboutbox{

 my $about_box = $mw->DialogBox(-title => "About", -buttons => ["OK"])
+;
 $about_box->add('Label', -anchor  => 'w',
                          -justify => 'center',
                          -text => qq(
This Simple Calculator was created Feb. 2004 by Eoin Murphy.
It was completed with the help of http:\/\/www.perlmonks.com, and thei
+r 
wonderful members. JamesNC and zentara to mention a few who helped.))-
+>pack(qw/-side top -anchor w/);


 $about_box->add('Label', -anchor  => 'sw',
                          -justify => 'left',
                          -text => qq(
eoin
eoinmurphy00\@hotmail.com
http:\/\/eoin.perlmonk.org))->pack(qw/-side top -anchor sw/);

$about_box->Show();


}