I always forget to reply-all :( ---------- Forwarded message ---------- From: Eli Frey Date: Thu, Mar 21, 2013 at 5:04 PM Subject: Re: [Haskell-cafe] A Thought: Backus, FP, and Brute Force Learning To: OWP Ah, ye old "point free programming" [1]. Yes when you first see this stile it's a bit alarming. I think it's valid to say you shouldn't take this too far, but IMHO it is a good thing. If it is any more enlightening, it is good to think of this style like building shell pipelines. Depending on your disposition, that might make you more dismayed though :). Personally I like this style because it allows me to very rapidly prototype my ideas. When I am fleshing some solution out I will write it nearly entirely in this style. As I am throwing code around and refactoring, I will reevaluate things and name my pipes and their inputs and outputs where it makes sense to increase legibility. I am sure that Bacchus is serious about this, but have no fear. Just because you can do this does not mean you have to. You are still free to name your inputs and outputs as much as you please. However, no-one is forcing you to. There is a parallel in languages that have syntactic support for OOP. obj.dothis.dothat.andthis.andthat.andanotherthing There is just as much debate about how far to go with method chaining, and when to name intermediate values. [1] https://en.wikipedia.org/wiki/Tacit_programming On Thu, Mar 21, 2013 at 4:21 PM, OWP wrote:

Thank you for this reply. This thought is more about Backus (he is cited quite a lot) and how much of his theory made it into Haskell and other commonly used functional programming.

In Backhu's paper ( http://www.thocp.net/biographies/papers/backus_turingaward_lecture.pdf), is his comparison between FP and Impertive as seen in 5.1 & 5.2 of "Programs for Inner Product".

When I start seeing that program described as:

"Def Innerproduct = (Insert +) o (ApplyToAll x) o Transpose"

I start getting queasy. When he later describes functional programming main purpose is to expand on that, I get worried. When he later explains how I don't need to use variables and just need to use "elementary substitution rule" for everything, I'm wondering if he's really serious about this.

From what you say, it doesn't sound as bad and I hope it isn't as I learn more.

Thanks for the reply.

On Wed, Mar 20, 2013 at 7:56 PM, Eli Frey wrote:

...

I have not read Bacchus' paper, so i might be off the mark here.

Functional code is just as simple (if not more so) to puzzle apart and understand as imperative code. You might find that instead of "stepping through the process" of code, you end up "walking the call graph" more often. FPers tend to break their problem into ever smaller parts before re-assembling them back together, often building their own vocabulary as they go. Not to say this is not done in imperative languages, but it is not so heavily encouraged and embraced. One result of this is that you can easily understand a piece of code in isolation, without considering it's place in some "process". It sounds as though you are not yet comfortable with this yet.

So yes, you might have to learn more vocabulary to understand a piece of functional code. This is not because the inner workings are obfuscated, but because there are so many more nodes in the call graph that are given names. You can still go and scrutinize each of those new pieces of vocabulary by themselves and understand them without asking for the author to come down from on high with his explanation.

Let's take iteration for example. In some imperative languages, people spend an awful lot of time writing iteration in terms of language primitives. You see a for loop. "What is this for loop doing?" you say to yourself. So you step through the loop imagining how it behaves as it goes and you say "Oh, this guy is walking through the array until he finds an element that matches this predicate." In a functional style, you would reuse some iterating function and give it functions to use as it is iterating. The method of iteration is still there, it has just nested into the call graph and if you've never seen that function name before you've got to go look at it. Again I don't mean to suggest that this isn't happening in an imperative language, just not to the same degree.

As well there is a bit of a learning curve in seeing what a function "does" when there is no state or "doing" to observe in it. Once you get used to it, I believe you will find it quite nice though. You have probably heard FPers extolling the virtues of "declarative" code. When there is no state or "process" to describe, you end up describing what a thing is. I for one think this greatly increases readability.

Good Luck! Eli

On Wed, Mar 20, 2013 at 3:59 PM, OWP wrote:

...

I made an error. I meant FP to stand for Functional Programming, the concept not the language.

On Wed, Mar 20, 2013 at 6:54 PM, OWP wrote:

...

This thought isn't really related to Haskell specifically but it's more towards FP ideal in general.

I'm new to the FP world and to get me started, I began reading a few papers. One paper is by John Backus called "Can Programming Be Liberated from the von Neumann Style? A Functional Style and It's Algebra of Programs".

While I like the premise which notes the limitation of the von Neumann Architecture, his solution to this problem makes me feel queasy when I read it.

For me personally, one thing I enjoy about a typical procedural program is that it allows me to "Brute Force Learn". This means I stare at a particular section of the code for a while until I figure out what it does. I may not know the reasoning behind it but I can have a pretty decent idea of what it does. If I'm lucky, later on someone may tell me "oh, that just did a gradient of such and such matrix". In a way, I feel happy I learned something highly complex without knowing I learned something highly complex.

Backus seems to throw that out the window. He introduces major new terms which require me to break out the math book which then requires me to break out a few other books to figure out which bases things using archaic symbols which then requires me to break out the pen and paper to mentally expand what in the world that does. It makes me feel CISCish except without a definition book nearby. It's nice if I already knew what a "gradient of such and such matrix" is but what happens if I don't?

For the most part, I like the idea that I have the option of Brute Force Learning my way towards something. I also like the declarative aspect of languages such as SQL which let's me asks the computer of things once I know the meaning of what I'm asking. I like the ability to play and learn but I also like the ability to declare this or that once I do learn. From Backus paper, if his world comes to a reality, it seems like I should know what I'm doing before I even start. The ability to learn while coding seems to have disappeared. In a way, if the von Neumann bottleneck wasn't there, I'm not sure programming would be as popular as it is today.

Unfortunately, I'm still very new and quite ignorant about Haskell so I do not know how much of Backus is incorporated in Haskell but so far, in the start of my FP learning adventure, this is how things seem to be seen.

If I may generously ask, where am I wrong and where am I right with this thought?

Thank you for any explanation

P.S. If anyone knows of a better place I can ask this question, please feel free to show me the way.

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