The Weird and The Wonderful

TheArchitectualizer wrote:

Microsoft actually considered removing recursive funcion from C#

Super Lloyd wrote:

As a rule recursion IS NOT bad. In fact it is use very much often!

Super Lloyd wrote:

Are you one of those religious warrior?

Super Lloyd wrote:

How do you write structure recognizer in a non recursive fashion?
i.e. how do you write thing such as a "Language compiler" or an "Object graph deserializer"?

Super Lloyd wrote:

How do you write structure recognizer in a non recursive fashion?
i.e. how do you write thing such as a "Language compiler" or an "Object graph deserializer"?

IEnumerable<Control> GetUITree(Control c)<br />
{<br />
 yield return c;<br />
 foreach(Control c in c.Children)<br />
  foreach(Control c2 in GetUITree(c))<br />
   yield return c2;<br />
}

void f()<br />
{<br />
 g();<br />
}

Super Lloyd wrote:

Why would getting the list of all control in a hierarchy this way be any bad?

void IterateUITree(Control c, Action<Control> listener)
{
  listener(c);
  foreach(Control child in c.Children)
    IterateUITree(child, listener);
}

/// <summary>
/// Converts a recursive data structure into a flat list.
/// </summary>
/// <param name="input">The root elements of the recursive data structure.</param>
/// <param name="recursive">The function that gets the children of an element.</param>
/// <returns>Iterator that enumerates the tree structure in preorder.</returns>
public static IEnumerable<T> Flatten<T>(this IEnumerable<T> input, Func<T, IEnumerable<T>> recursion)
{
	Stack<IEnumerator<T>> stack = new Stack<IEnumerator<T>>();
	try {
		stack.Push(input.GetEnumerator());
		while (stack.Count > 0) {
			while (stack.Peek().MoveNext()) {
				T element = stack.Peek().Current;
				yield return element;
				IEnumerable<T> children = recursion(element);
				if (children != null) {
					stack.Push(children.GetEnumerator());
				}
			}
			stack.Pop().Dispose();
		}
	} finally {
		while (stack.Count > 0) {
			stack.Pop().Dispose();
		}
	}
}

Control[] roots = { control };
var flatList = roots.Flatten(c=>c.Children);

void IEnumerable<Control>IterateUITree(Control c)<br />
{<br />
  var result = new List<Control>();<br />
  result.Add(c);<br />
  foreach(Control child in c.Children)<br />
    IterateUITree(child, result);<br />
  return result;<br />
}<br />
void IterateUITree(Control c, List<Control> result)<br />
{<br />
  result.Add(c);<br />
  foreach(Control child in c.Children)<br />
    IterateUITree(child, result);<br />
}<br />

<br />
(* Fibonacci Number formula *)<br />
let rec fib n =<br />
    match n with<br />
    | 0 | 1 -> n<br />
    | _ -> fib (n - 1) + fib (n - 2)<br />
 <br />
(* An alternative approach - a lazy recursive sequence of Fibonacci numbers *)<br />
let rec fibs = seq {<br />
    yield! [1; 1];<br />
    for (x, y) in Seq.zip fibs (Seq.skip 1 fibs) -> x + y }<br />
 <br />
(* Print even fibs *)<br />
[1 .. 10]<br />
|> List.map     fib<br />
|> List.filter  (fun n -> (n mod 2) = 0)<br />
|> printlist<br />
 <br />
(* Same thing, using Comprehension syntax *)<br />
[ for i in 1..10 do<br />
    let r = fib i<br />
    if r % 2 = 0 then yield r ] br />
|> printlist<br />

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Linq
{
    class Program
    {
        static void Main(string[] args)
        {
            ListFiles(new DirectoryInfo("c:\\"));
        }

        static void ListFiles(DirectoryInfo dir)
        {
            var Directories = from dirs in dir.GetDirectories()
                              orderby dirs.FullName
                              select dirs;

            foreach(DirectoryInfo directory in Directories)
            {
                Console.WriteLine("Directory: <" + directory.FullName + "> contains the following files:");

                var Files = from file in directory.GetFiles()
                            orderby file.FullName
                            select file;

                foreach (FileInfo file in Files)
                {
                    Console.WriteLine("---" + file.FullName);
                }
            }
        }
    }
}

C:\
  A
    A1
      A11
        File1
        File2

static void ListDirectories(DirectoryInfo dir)
{
    var BaseDir = from dirs in dir.GetDirectories()
                         orderby dirs.FullName
                         select dirs;

    foreach (DirectoryInfo thisDir in BaseDir)
    {
        var TheDirectory = from dirs in thisDir.GetDirectories("*", SearchOption.AllDirectories)
                           orderby dirs.FullName
                           select dirs;

        Console.WriteLine("Directory: <" + thisDir.FullName + "> contains the following directories:");

        foreach (DirectoryInfo directory in TheDirectory)
        {
            Console.WriteLine("  --[" + directory.FullName + "]");
        }
    }
}