leonoff / medusa

Immutable and persistent collections for PHP

Medusa

Immutable and persistent collections for PHP.

Life would be a lot simpler if we had immutable data structures. Code would be easier to understand, easy to test and free of side-effects. Being immutable is not all, these data structures must be efficient. By making them persistent, collections reuse internal structure to minimize the number of operations needed to represent altered versions of an instance of a collection.

Installation

To install this library, run the command below and you will get the latest version

composer require keyvanakbary/medusa

Usage

Persistent Stack

$s = Medusa\Stack\PersistentStack::createEmpty();

$s1 = $s->push(1);
$s2 = $s1->pop();
echo $s1->peek();//1
echo $s2->peek();//Runtime exception

Complexity

operation	big-O
push	O(1)
peek	O(1)
pop	O(1)
isEmpty	O(1)
count	O(1)

Persistent Queue

$q = Medusa\Queue\PersistentQueue::createEmpty();

$q1 = $q->enqueue(1);
$q2 = $q1->dequeue();
echo $q1->peek();//1
echo $q2->peek();//Runtime exception

Complexity

operation	big-O
isEmpty	O(1)
peek	O(1)
enqueue	O(1)
dequeue	O(1) in average, O(n) in some cases
count	O(1)

Persistent AVL Tree

$t = Medusa\Tree\PersistentAvlTree::createEmpty();

$t1 = $t->add(1, 'one');
$t2 = $t1->remove(1);
echo $t1->search(1)->value();//one
echo $t2->lookup(1);//Runtime exception

Complexity

operation	big-O
isEmpty	O(1)
value	O(1)
key	O(1)
search	O(log(n))
add	O(1)
search	O(log(n))
contains	O(log(n))
height	O(1)
lookup	O(log(n))

Persistent Red-Black Tree

$t = Medusa\Tree\PersistentRedBlackTree::createEmpty();

$t1 = $t->add(1, 'one');
$t2 = $t1->remove(1);
echo $t1->search(1)->value();//one
echo $t2->lookup(1);//Runtime exception

Complexity

operation	big-O
isEmpty	O(1)
value	O(1)
key	O(1)
search	O(log(n))
add	O(1)
search	O(log(n))
contains	O(log(n))
height	O(1)
lookup	O(log(n))
min	O(log(n))
removeMin	O(log(n))