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Re: My Most Important C++ Aha! Moments...Ever
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Posted: Oct 2, 2006 6:36 AM
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> > > My best Aha! moment wasn't directly related to C++
> > > although it uses it. I realised that programming
> > doesn't
> > > need functions, execution points or any execution
> > control
> > > statements at all. [...] It's
> > a
> > > a 30 year old idea that will probably take another 30
> > > years to come to fruition by the looks of things.
> >
> > This sounds interesting, could you elaborate on it, or
> > give any pointers to where to learn about this idea?
>
> I'm talking about specifying instructions on data and not
> the machine. It can come in any form. Right now, only
> data flow "languages" come close, but not completely. I
> took it for granted. I didn't understand the power that
> this gives.
>
> I don't know where I could give you a link because there's
> nothing out there that fully exploits this power. I'm
> working on a tool for this though.
>
> The simplest way I could describe this is by comparison.
> When we add two numbers, we take for granted that we're
> e asking the computer to do it.
>
> a = b+c;
>
> is actually
>
> a = CPU->Add(b,c);
Well, not really from a functional programming view of things, i.e. "a = b+c" _declares_ that a is the sum of b and c; no instruction about how to do that, or in which order (compared to other things) is given. However, that distinction may not be important in this context.
That's also something like a 30 year old idea.
Indeed, declarative programming (such as functional programming) is recognised as a powerful way of doing things, but like other "paradigms", there may be areas where it may be hard to write something in a purely declarative style.
We have the example in HTML, which is declarative (it only specifies that something is a header, another thing is a paragraph, etc.; nothing about how it's supposed to look (unless you use presentational markup...)). However, for behaviour, JavaScript is typically used, an imperative language, again.
However, recent developments of HTML (XHTML 2.0) aims to take care of 90% or so of what we now use scripting for (validation, calculations, etc.) using declarative constructs.
It seems you're talking about something quite different, though.
> I don't like that. I'd rather specify that b and c should
> be added and sent to a.
>
> (b,c)->ADD->(c).
>
> I found the majority of people think that the two Add
> statements above are the same. They're not even
> equivalent, but that's irrelevant. One is machine
> specific (low level), the other is not.
Regarding the last paragraph: The same can be said for the distinction between imperative and declarative programming: a=b+c is a statement about the relationship between a, b and c, but it _can_ also be viewed as the instruction: "Add b and c, and assign the result to a".
> This seemingly
> small detail in the previous sentence can open up a whole
> new area in the computing industry. Understanding this
> was my AHA! moment.
I see. Hm, you say the variables are _streams_... I still have a little difficulty understanding what is meant by the pseudo-code you gave. How is it different from the FP-interpretation of a=b+c?
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