Comments for Pavel Fatin

Comment on Scala for Project Euler by Pavel

Pavel — Thu, 02 Jun 2011 14:18:36 +0000

Rhys, I usually run such code directly, either from command line (“scala problem1.scala”) or from IntelliJ IDEA, which supports running Scala scripts.

Additionally, I used a simple application to measure code execution time (to exclude JVM and Scala startup time).

Comment on Scala for Project Euler by Rhys

Rhys — Wed, 01 Jun 2011 21:20:45 +0000

Hi, thanks for posting your solutions. They are very useful for comparing against my own and learning new techniques.

I have a mundane question: how do you run these? In the REPL, in an IDE? Do you package them in individual objects that extend App, or do you have a separate object that calls them and displays the result?

Comment on Sleeptracker Pro Review by Pavel

Pavel — Sun, 20 Mar 2011 15:07:53 +0000

So, I've open sourced SleepArchiver.

Comment on Scala for Project Euler by Mark

Mark — Wed, 16 Mar 2011 15:21:16 +0000

Of course. I have a memory like a sieve. I was bitten by this a couple of years ago.

Thanks.

Comment on Scala for Project Euler by Pavel

Pavel — Tue, 15 Mar 2011 11:22:23 +0000

Mark, lazy modifiers are needed to prevent “forward reference extends over definition of value” compilation error when such code is put into a method (like “main”).

Comment on Scala for Project Euler by Mark

Mark — Mon, 14 Mar 2011 15:13:01 +0000

Some interesting code, but I was wondering why you are using lazy vals? The examples run the same without the vals being lazy…

Comment on Scala for Project Euler by ndesmoul

ndesmoul — Mon, 03 Jan 2011 09:57:13 +0000

To complement my previous message, an interesting project is ScalaCLPlugin:
https://code.google.com/p/scalacl/wiki/ScalaCLPlugin

“The ScalaCL Compiler Plugin optimizes simple generalistic Scala loop-like calls by transforming them into equivalent while loops, which are much faster.”

So even with pure functionnal programming, you could potentially obtain good performances.
It could be interesting to compare the performances with and without the use of this compiler plugin.

Comment on Scala for Project Euler by ndesmoul

ndesmoul — Thu, 16 Dec 2010 12:26:25 +0000

Scala is an hybrid imperative/functional language, so even if the use of vals is encouraged, “No vars” is not an absolute rule.
Quoting “Programming in Scala”, you have to prefer using val as much as possible unless “you have a specific need and justification for them”. Well in this case it is just 2 to 3 times faster (a potentially valid justification to me), and the whole method still has no side effects.
Just to say that the pure functionnal style programming may be the most elegant, but not always the most efficient. When you deal with time critical code, it may be important to have this in mind.

Comment on Scala for Project Euler by Pavel

Pavel — Wed, 15 Dec 2010 19:50:19 +0000

> for problem 1 the following code gives the same result and is clearly faster…

“No vars” is the first rule of idiomatic Scala

Scala encourages “functional style” of programming, with no mutable states and no side-effects. I recommend you to check “Next steps in Scala / Learn to recognize the functional style” in “Programming in Scala” book.

Comment on Scala for Project Euler by Pavel

Pavel — Wed, 15 Dec 2010 19:47:43 +0000

> I also cooked up an alternative solution for problem 5 and figured you might like it

Nice! The code is still concise and “functional” but it runs much faster than mine.