Wednesday, 21 June 2017

Java Calculator 2

Following previous post, I've fixed this - now is not nessessery to use fully paranthized expression; the operator precedence is set and can be changed using paranthesis. Instead of binary tree, I parsed expression to postfix - Reverse Polish Notation Rocks :).
Code, of course, on Github. Till the next time!

Monday, 12 June 2017


Trying to get new skills: objective programming, I've started to code in Java. The simple project: Calculator. Expression string is parsed to Binary Abstract Syntax Tree and then recursively evaluated.
Code on Github. Till the next time!

Wednesday, 17 May 2017

Thursday, 30 March 2017

New Class in C++ Biginteger Library!

I've started developing a C++ wrapper for GMP - high precision arithemtic library in C; updates on github today - bigrationals added! Only basic functions for now, but development in progress:)

Thursday, 23 March 2017

C++ GMP Wrapper

Recently beeing busy - writing, in C++, wrapper for GMP LibraryCode here - you are invited to improve it!:)

Wednesday, 8 March 2017

Scala Trees

Recently, I've been playing with functional programming, ADT to be precise, and this is the outcome - trees implementation in Scala.
Data are created in common way as a Scala trait:

sealed trait Tree[+A]
case object EmptyTree extends Tree[Nothing]
case class Node[A](value: A, left: Tree[A], right: Tree[A]) extends Tree[A]

All looks Okay, lets create some trees and functions.

val tree = Node(10, Node(5, EmptyTree, EmptyTree), Node(15, EmptyTree, EmptyTree))

No problem, but at least for integer binary trees, we can right now do better: create a function to join elements to the tree:

def addToTree(elem: Int, tree: Tree[Int]): Tree[Int] = {
if (isTreeEmpty(tree)) Node(elem, EmptyTree, EmptyTree)
else if (elem == loadTree(tree)) tree
else if (elem < loadTree(tree)) Node(loadTree(tree), addToTree(elem, leftBranch(tree)), rightBranch(tree))
else Node(loadTree(tree), leftBranch(tree), addToTree(elem, rightBranch(tree)))

This is the standard way to add elements to a binary tree, we can use it in a loop and don't need to worry about memory - we use persistent data structure.

Two sample functions operate on a tree:

def length[A](tree: Tree2[A]): Int =
tree match {
case EmptyTree => 0
case Node(x, left, right) => length2(left) + 1 + length2(right)

def maxDepth[A](tree: Tree2[A]): Int =
tree match {
   case EmptyTree => 0
   case Node(x, left, right) =>
   var lmax = maxDepth2(left)
   var rmax = maxDepth2(right)
   if (lmax > rmax) lmax + 1
      else rmax + 1

They do what their names promise: count nodes and maximum depth of the trees. Finally map over the tree:

def treeMap[A, B](tree: Tree2[A])(f: A => B): Tree2[B] =
tree match {
case EmptyTree => EmptyTree
case Node(x, left, right) => 
Node(f(x), tree2Map(left)(f), tree2Map(right)(f))
We can, in a similar way, all the needed function like foldl, traversing a tree and more. Code, including not implemented here functions helped to design joining element to tree, as usually on github. Till the next time!