The Monty Hall problem is a counter intuitive problem in probability mathematics that deals with picking the right prize from a set of three doors. The problem is named after the television celebrity Monty Hall and is loosely based on the USA game show Let's Make a Deal.
Following on from my last post about sorting colors I have been thinking about different ways of sorting colors. I have been looking at interfaces that allow people to select colors and they will quite normally have a band of colors that does look nicely sorted. As it turns out this is perfectly possible to do if the colors are normalised to remove light and dark variations of different colors.
I came across this sorting algorithm the other day called 'bogo sort'. This is a sort of joke sorting algorithm that is highly ineffective at actually sorting arrays. The name comes from the word 'bogus'.
Here is how it works.
I have been doing some reading and watching lectures of programming theory recently and I was reminded of this algorithm I learned about in university. Binary searching an array is a divide and conquer algorithm that takes an array and searches for a value in that array by splitting the array into halves. The algorithm works like this.
Sorting colors is the sort of thing that you never really think about until you need to do it. Sorting a bunch of items by their color is useful in a number of applications, but the simplest is just to display items to the user in a more controlled manner. As it happens sorting with colors is a much more complex topic than I originally thought and required digging into quite a bit more maths than I expected.
Incidentally, there is a whole world of color maths that I didn't know existed until I started looking into this. It was worth learning about though.
PHPNW is the 8th annual PHPNW Conference, and I think I'm lucky to be one of the few who have attended every year. This was something that Jeremy Coates mentioned out as we sat down the introductory session, but it was also good to see lots of new people attending the conference as well. It was a great conference with a great community feeling.
The keynote this year was by Meri Williams, who talked about Stealing People Lessons from Artificial Intelligence. Meri's career has been in both development and project management and she was able to use lessons learnt during her PhD thesis on artificial intelligence in order to think about how people respond to work. The concept sounds a little un-emotional at face value, but part of the principles of AI is making sure that all agents have their own goals. Meri was a funny and engaging speaker who talked about all kinds of interesting aspects of how people learn and grow.
At the LAMP and Beyond III event (run by PHPNW) this weekend we set ourselves the task of giving PHP7 a go. Below is some nodes from that session.
This assumes that you’ve already installed PHP5.6 along with Apache and MySQL. Installing PHP5.6 via apt-get is fine as we just need some of the dependencies to be present.
To get the the code for PHP7 you need to clone from the PHP repo on Github.
New in PHP 5.5 is a group of functions that deal with password hashing and verification. This is such a common thing for PHP applications to do that it was decided to include it into the core of PHP. They effectively solve the problem of hashing and comparing passwords that just about every PHP developer has implemented at one point or another.
There are only a few functions available but they provide all of the functionality needed to create a hash value from a password, check if the hash is valid and to check if the password hash needs to be recreated.
Getting the first or last item from an array in PHP is usually quite easy. If you create an array and then add a bunch of values to it then the array index will increment by 1 for every element you add. This means that in order to get the first element from an array you just reference the default stating position (0). To get the last item in the array the index key will be the length of the array, minus 1. Here is some example code showing this.
Alternative PHP Cache (APC) is an opcode and variable cache for PHP. When you run a PHP script it is first compiled into a series of opcodes which are then used by the Zend engine to run the program before being discarded. APC sits between the source files and the Zend engine and will stop the opcodes generated during the PHP script execution being thrown away. This means that when you run a PHP script a second time the work done in generating the opcodes has already been done and the script will execute faster.