VList: Difference between revisions

</pre>

=={{header|Perl 6}}==

{{trans|Go}}

{{trans|Kotlin}}

<lang perl6>#!/usr/bin/env perl6

class vList {

subset vEle of Any; # or Str

class vSeg {

has $.next is rw is default(Nil) ;

has vEle @.ele is rw ;

}

has vSeg $.base is rw is default(vSeg.new(ele=>()));

has Int $.offset is rw is default(0) ;

method Index(Int $i is copy --> vEle) { # method to locate the kth element

if $i ≥ 0 {

loop ( $i += self.offset, $_ = self.base; $_.defined; $_ := $_.next) {

($i < my $len = .ele.elems) ?? return .ele[$i] !! $i -= $len

}

}

die "index out of range"

}

method cons(vEle \a --> vList) { # method to add an element to the front

if not self.base.ele.Bool { # probably faster than .elems ?

self.base.ele.push: a ;

return self;

} elsif self.offset == 0 {

my \L2offset = (self.base.ele.elems * 2) - 1 ;

my \s = vSeg.new(next => self.base, ele => flat Nil xx L2offset, a);

return vList.new(base => s, offset => L2offset )

}

self.base.ele[--self.offset] = a;

return self

}

# obtain a new array beginning at the second element of an old array

method cdr(--> vList) {

die "cdr on empty vList" unless self.base.defined;

return self if ++self.offset < self.base.ele.elems;

return vList.new(base => self.base.next)

}

method Length(--> Int) { # method to compute the length of the list

return 0 unless self.base.defined;

return self.base.ele.elems*2 - self.offset - 1

}

method gist { # (mis)used to create output similar to Go/Kotlin

return '[]' unless self.base.ele.Bool;

my @sl = self.base.ele[self.offset .. *];

loop ($_=self.base.next; $_.defined; $_:=$_.next) { @sl.append: .ele }

return "[" ~ @sl.Str ~ "]"

}

method printStructure { # One more method for demonstration purposes

say "offset: ", self.offset;

loop ( $_ = self.base; $_.defined ; $_ := $_.next ) { .ele.say }

}

}

my $v := vList.new;

say "zero value for type. empty vList: ", $v;

$v.printStructure;

say " ";

$v := $v.cons($_.Str) for 6 … 1;

say "demonstrate cons. 6 elements added: ", $v;

$v.printStructure;

say " ";

$v := $v.cdr;

say "demonstrate cdr. 1 element removed: ", $v;

$v.printStructure;

say " ";

say "demonstrate length. length = ", $v.Length;

say " ";

say "demonstrate element access. v[3] = ", $v.Index(3) ;

say " ";

$v := $v.cdr.cdr;

say "show cdr releasing segment. 2 elements removed: ", $v;

$v.printStructure;</lang>

{{out}}

<pre>zero value for type. empty vList: []

offset: 0

[]

demonstrate cons. 6 elements added: [1 2 3 4 5 6]

offset: 1

[(vEle) 1 2 3]

[4 5]

[6]

demonstrate cdr. 1 element removed: [2 3 4 5 6]

offset: 2

[(vEle) 1 2 3]

[4 5]

[6]

demonstrate length. length = 5

demonstrate element access. v[3] = 5

show cdr releasing segment. 2 elements removed: [4 5 6]

offset: 0

[4 5]

[6]