Oscar Del Ben

Rspec book announced

So, after more than a year of voices about it, it looks that the pragmatic programmers finally announced a book about rspec. The title will be available on april of the next year and I don't know if there will be a beta version.

Solution of project Euler #1

This is the first of a series of articles about project euler, a set of mathematics problems of incremental difficulty to be solved with your preferred programming language. You can find more about this on the project website.

PROBLEM N 1

This is the announcement of the first problem:

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

Solution using Ruby

The solution above is extremely simple and readable, which is why I love ruby and use it in my every day work:

def is_a_multiple_of_3_or_5?( n )

  n % 3 == 0 || n % 5 == 0

end

counter = 0

  

3.upto( 999 ) do |n|

  counter += n if is_a_multiple_of_3_or_5?( n )

end

puts counter

Solution using Erlang

I'm totally new to Erlang, but I've worked to a one-line solution using a comprehension list:

Result = lists:sum([ N || N <- lists:seq(1,999), N rem 3 == 0 orelse N rem 5 == 0 ]).

Basically, I create a list of all numbers under 1000 which are either multiples of three or multiples of five, then I've calculated the sum of all those numbers with the native procedure lists:sum.

Solution using Scheme

I love scheme, although I've never done that much with it:

(define total

(lambda (n counter)

(cond

((> n 999) counter)

((or (= (remainder n 3) 0) (= (remainder n 5) 0))

(total (+ n 1) (+ n counter)))

(else (total (+ n 1) counter)))))

(display (total 3 0))

Conclusion

It was very simple to figure out the solution for this problem, but the point here for me is to exercise my programming skills with a series of problems. Feel free to send me your suggestions in the comments, especially about Erlang and Scheme, where I'm still new, and I need to improve.

The mind map book review

I became more interested about mind maps after reading pragmatic thinking and learning, so i went to amazon to find a good book about mind mapping. I had enough luck to find The Mind Map Book: How to Use Radiant Thinking to Maximize Your Brain's Untapped Potential, which is written directly by Tony Buzan, the creator of modern mind maps techniques.

The book is divided in three major parts, the first part explain why the use of mind maps is efficient and how it reflect the structure of our mind in the act of learning and thinking. The second part introduces the effective way of producing a mind map, explaining the difference between various techniques and methods. The last part of the book explores different environments like family, work and learning where the use of mind mapping could dramatically improve the experience.

Conclusion: be sure to read this book as soon as possible if you haven't already, even if you think that you are not interested in map mapping.

High performance web sites book review

This is a book about fast web sites.

Steve Souders, the author, was involved in the performance revision for yahoo, and collected his experience in the book high performance web sites.

The first important lesson, is that the 80-90 percent of loading time, is not time about html rendering (back-end), but instead is devoted at browser things, such as loading images, scripts and other factors that you will learn in the course of the book, which in fact is written with the purpose of reducing that amount of time.

High performance web sites  is written in a concise way, meaning that you'll find exactly the informations you need, collected in 14 easy to follow rules, most of them directly applicable for every web site.

A personal note: even if the book is oriented at front end developers, i found the chapters about conditional tags and http headers to be very interesting for the rest of us, since rails 2.2 will introduce custom helpers for take advantage of them.