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use v6d;
###############################################################################
=begin comment
Perl Weekly Challenge 095, Task #2: Demo Stack
=end comment
###############################################################################
#--------------------------------------#
# Copyright © 2021 PerlMonk Athanasius #
#--------------------------------------#
#==============================================================================
unit class Stack;
#==============================================================================
#------------------------------------------------------------------------------
# Exception classes
#------------------------------------------------------------------------------
class Empty is Exception { }
class Empty::Pop is Stack::Empty
{
method message() { 'ERROR: Cannot pop() an empty stack'; }
}
class Empty::Top is Stack::Empty
{
method message() { 'ERROR: There is no top() on an empty stack'; }
}
class Empty::Min is Stack::Empty
{
method message() { 'ERROR: There is no min() for an empty stack'; }
}
#------------------------------------------------------------------------------
# Stack attributes
#------------------------------------------------------------------------------
has Bool $!throw;
has Int:D $!top = -1; # Index of the top element: -1 indicates an empty stack
has Real:D @!items;
#------------------------------------------------------------------------------
submethod BUILD( Bool:D :$throw = True )
#------------------------------------------------------------------------------
{
$!throw = $throw;
}
#------------------------------------------------------------------------------
method push( Real:D $item )
#------------------------------------------------------------------------------
{
@!items.push: $item;
++$!top;
}
#------------------------------------------------------------------------------
method pop( --> Real )
#------------------------------------------------------------------------------
{
my Real $item;
if $!top >= 0
{
$item = @!items.pop;
--$!top;
}
elsif $!throw
{
Empty::Pop.new.throw;
}
return $item;
}
#------------------------------------------------------------------------------
method top( --> Real )
#------------------------------------------------------------------------------
{
my Real $item;
if $!top >= 0
{
$item = @!items[ $!top ];
}
elsif $!throw
{
Empty::Top.new.throw;
}
return $item;
}
#------------------------------------------------------------------------------
method min( --> Real )
#------------------------------------------------------------------------------
{
my Real $min;
if $!top >= 0
{
$min = @!items[ 0 ];
for 1 .. @!items.end -> UInt $i
{
my Real $new-min = @!items[ $i ];
$min = $new-min if $new-min < $min;
}
}
elsif $!throw
{
Empty::Min.new.throw;
}
return $min;
}
#------------------------------------------------------------------------------
method display( --> Str:D )
#------------------------------------------------------------------------------
{
my Str $stack = "Stack: (empty)\n";
if $!top >= 0
{
my UInt $width = @!items[ $!top ].chars;
for @!items[ 0 .. $!top - 1 ] -> Real $item
{
my UInt $new-width = $item.chars;
$width = $new-width if $new-width > $width;
}
my Bool $top = True;
my Str $bar = '+-%s-+'.sprintf: '-' x $width;
$stack = "Stack: $bar\n";
for @!items.reverse -> Real $item
{
$stack ~= " | %*s |%s\n %s\n".sprintf:
$width, $item, $top ?? ' <- top' !! '', $bar;
$top = False;
}
}
return $stack;
}
##############################################################################
|
