Comments on: Writing better code: it’s imperative that you are declarative

By: Sergey

Sergey — Wed, 28 Apr 2010 08:24:33 +0000

Andrew, it’s a very good article and I absolutely agree with you. I think that who are not agree with you should read very nice book “Functional Programming for the Real World with examples in F# and C# by Tomas Petricek and Jon Skeet” (yes, Jon Skeet) or just one chapter from this book “1.2 Functional programming by example” and they will change their mind very quickly :)

By: Andrew

Andrew — Sat, 24 Apr 2010 13:45:46 +0000

@Michael Chandler – You make an excellent point about parallelization – declarative code is much easier to parallelize! Thank you for your comment!

By: Michael Chandler

Michael Chandler — Sat, 24 Apr 2010 13:22:05 +0000

I'm surprised to see so many people disagreeing with you. I totally agree with you that the readability of the second and third examples prevail. Clearly in this case it's a trivial example, but breaking out a lambda into a separate method is a great way of self-documenting what its purpose is.

It's also disappointing to see that people assume that declarative performance is going to be worse than that of the imperative counterpart. How does your imperative, state-based code stack up when you need to perform in parallel? Functional / declarative programming seems to be the way forward in addressing much of these problems. You can't just stick an .IsParallel onto the end of your imperative code, that's for sure.

The comment about using & vs % is just silly. Either work fine. In my opinion modulus is a 'higher level of abstraction' than the bitwise operator, so I would generally using it. (Yes, even if it's an operation slower.)

I've added your blog to my Google Reader. :)

By: Andrew

Andrew — Sat, 17 Apr 2010 18:24:04 +0000

@John Haugeland - I appreciate the Erlang example, your use of list.sum and list.seq both greatly contribute to its declarative nature. I am not completely certain what you meant by these two statements:

"Thanks for not confusing the effects of one particular language’s syntax with those of a style of language."
"You’re really just showing off the effects of a bad formatting style."

Would you mind explaining a bit more?

By: John Haugeland

John Haugeland — Sat, 17 Apr 2010 18:10:48 +0000

Alternatively,

int Total = 0; for (int i=0; i<100; ++i) { if (i%2==0) { Total += i; }}

You're really just showing off the effects of a bad formatting style.

By: John Haugeland

John Haugeland — Sat, 17 Apr 2010 18:09:41 +0000

Er.

lists:sum( [ X || X <- lists:seq(1,100), x%2 == 0] )

That's completely imperative code, sir. Thanks for not confusing the effects of one particular language's syntax with those of a style of language.

By: Ed The Dev .com » Blog Archive » Declarative programming

Ed The Dev .com » Blog Archive » Declarative programming — Sat, 17 Apr 2010 04:42:41 +0000

[...] togaroga.com/2010/03/writing-better-code-its-imperative-that-you-are-declarative/ Posted in Random Geekiness by Edward Delaporte RSS 2.0 [...]

By: Andrew

Andrew — Fri, 16 Apr 2010 23:24:08 +0000

@hobbit125 - Private methods that are singular in focus like I have used here are not only appropriate but actually desired in some cases. I did consider using a named lambda expression to check for evenness but given the introductory nature of the article I decided against it. I also don't think a comment explaining the evenness check makes a whole lot of sense given that this article is supposed to be an introduction on declarative code. You could make a case that my isEven method is unnecessary but I could just as easily make the case that you are missing the point of the article.

I do appreciate your alternative method for checking a number for evenness. From the way you phased your statement someone could get the impression that you consider your approach to be correct and my approach incorrect. Given the fact that i & 1 == 0 provides the same exact results as i % 2 == 0 and takes about the same amount of time to execute I thought it was important to point out that both solutions are correct and can be used interchangeably.

Finally, I am happy to report that I am in no way a superstitious person at all! I simply prefer to use the actual names of the types as they are defined in their assemblies instead of their corresponding aliases. Given the fact that the aliases are changed by the compiler into their respective type names I like to think that I am saving the compiler that trouble and therefore compiling my code at a faster rate than others who prefer to use aliases.

By: Andrew

Andrew — Fri, 16 Apr 2010 22:45:02 +0000

@Dean Camera – Yes declarative code like this has the potential to have poorer performance but I believe that it is better to write the most readable code first. If it becomes apparent (through the use of a profiler) that the code is creating a bottleneck in the application’s performance only then would I consider changing it to an imperatively-styled solution.

By: hobbit125

hobbit125 — Fri, 16 Apr 2010 03:35:06 +0000

Eww...polluting the class with a one-off method. At least, use a named local lambda. Better, don't bother. Just inline it. Most people are familiar with even check statements, and if it's that big of a deal, throw a comment at the end of the Where line.

Also, this is how you check for evens: (i & 1) == 0.

Also, do you have some superstitious reason for not liking keyword types?