From: Josh Cheek <josh.cheek@...>
Date: 2011-04-04T03:59:49+09:00
Subject: Re: Lambda Shambda

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On Sun, Apr 3, 2011 at 6:50 AM, Phillip Gawlowski <
cmdjackryan@googlemail.com> wrote:

>
> Though, considering that LISP was one of, if not the, first language
> to use the lambda calculus as basis for a programming language, it is
> certainly a forefather of today's crop of functional programming
> languages, like Scheme, ML, Erlang, Haskell, or F#.
>
>
I'm not particularly familiar with its history, but I don't think Common
Lisp was the original dialect of Lisp.


On Sun, Apr 3, 2011 at 7:17 AM, Everett L Williams II
<rett@classicnet.net>wrote:

> *Let's not pay too much attention to the code snobs on here. I've yet to
> see a recursive function that is more efficient than a more linearly coded
> function that accomplishes the same thing,


There are many types of efficiency, there is also efficiency of
comprehension, and implementation, and it is much easier to comprehend and
implement recursion in many situations.

Here is an example of a Binary Search Tree with a recursive_print method and
a "linearly coded function that that accomplishes the same thing" (I assume
by "linear" you mean "imperative"). I can barely comprehend the linear
version, and I wrote it. If you can come up with a better version, please
post it.

class BST

  attr_accessor :left , :right , :data

  def << new_data
    if !data
      self.data = new_data
    elsif new_data <= data
      ( self.left  ||= BST.new ) << new_data
    else
      ( self.right ||= BST.new ) << new_data
    end
    self
  end

  # this is for simplicity of the exercise, in reality it
  # would be an each method and the code using it
  # would make it print
  def recursive_print
    left  && left.recursive_print
    data  && puts(data)
    right && right.recursive_print
  end

  def iterative_print
    todo = []
    crnt = self
    loop do
      if crnt && crnt.left
        todo.push crnt
        crnt = crnt.left
      elsif crnt && crnt.right
        puts crnt.data
        crnt = crnt.right
      else
        puts crnt.data if crnt && crnt.data
        crnt = todo.pop
        break unless crnt
        puts crnt.data if crnt.data
        crnt = crnt.right
      end
    end
  end
end


root = BST.new << 7 << 3 << 1 << 0 << 2 << 5 << 4 \
       << 6 << 11 << 9 << 8 << 10 << 13 << 12 << 14

root.recursive_print
puts
root.iterative_print


I decided to benchmark it, just to see how much faster it really is. And it
actually turns out to be slower. In this case, the recursive version is not
only elegant, easier to read, write, and comprehend, but it is also faster.

def no_output
  stdout = Object.new
  def stdout.write(*params) end
  def stdout.puts(param) end
  $stdout = stdout
  yield
ensure
  $stdout = STDOUT
end

require 'benchmark'
Benchmark.bm 10 do |b|
  b.report "recursive" do
    no_output do
      100_000.times { root.recursive_print }
    end
  end
  b.report "linear" do
    no_output do
      100_000.times { root.iterative_print }
    end
  end
end

# RESULTS
#                 user     system      total        real
# recursive   0.840000   0.000000   0.840000 (  0.843655)
# linear      1.040000   0.010000   1.050000 (  1.059313)



On Sun, Apr 3, 2011 at 8:13 AM, Martin DeMello <martindemello@gmail.com>wrote:

>
> No less a person than Simon Peyton Jones has called Excel "the world's
> most popular functional language".
>
> http://research.microsoft.com/en-us/um/people/simonpj/papers/excel/
>
> martin
>
>
It might be easier if you guys could show how one writes a program in excel.
OP was talking about a web app, complete with authentication, authorization,
cookies, "etc". I can't even conceive of how one would go about doing such a
thing. I wouldn't even know how to execute an Excel program (do you make an
executable? do you invoke it on the command line? is there an interpreter?
compiler?). Here are some examples of programs I've written this semester in
Ruby:
* A Shoes app to help me in my Chem lab by watching the time and telling me
to take a measurement every n seconds. (
http://img209.imageshack.us/img209/2602/93593675.png)
* A program to go through my music and rename all my mp3s to
"#{mp3.tag['artist']} - #{mp3.tag['title']}", it is invoked on the command
line, you pass it the directory with the mp3s that it should rename.
* A program to create Conway's game of life videos (
http://vimeo.com/21594165)

Is it even possible (let alone viable) to do any of this in Excel? And if
so, then why do they bother bundling VBA with Excel? Seems redundant.

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