Trouble with OOP

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Subtyping, Subclassing, and Trouble with OOP.

Excerpt:

What makes this problem more unsettling is that both you and I tried to do everything by the book. We wrote a safe, typechecked code. We eschewed casts. g++ (2.95.2) compiler with flags -W and -Wall issued not a single warning. […] And yet, despite all my efforts to separate interface and implementation, I failed. Should a programming language or the methodology take at least a part of the blame?

A lot of people miss the point with Object Oriented Programming (OOP) – this author gets it.

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Best and Free Programming Ebooks

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(updated / switched link to source article on stack overflow)

So, I wrote my list of some unique programming texts. But on the more practical side, there’s this:

Best and Free Programming Ebooks.

Free full texts, covering: Bash, C, C++, C#, Common Lisp, Haskell Java, JavaScript, Lua, Objective-C, Perl, PHP, PowerShell, Prolog, Python, Ruby, SQL, x86 assembly, algorithms, version control, and a couple other topics.  I’ll still be putting together my own preferred lists, but half of what I’ve got is already on this list.

Yeah, Toast

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So, for those not familiar, I go by toast` on the programming language IRC channels. So when I saw this video come up on youtube, with Mr. Engineer (my preferred TF2 class), I had a feeling of a certain kind of awesome. Like it was meant for me, or something.

Yeah, Toast!!

Is it better to remain blissfully unaware…

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I was once asked “why bother learning these other languages, if you can’t use them”. It hadn’t occurred to this person that I code off hours. I’ve also been asked “what if you find these other languages actually are better than C++? Won’t you find it depressing having to code in a normal language then?”

It’s a good question. I don’t know if there’s one answer, but I’ve found mine.

Learning Lisp, Haskell, Python, and others has given me a greater appreciation for computer science, for the theory and universe of knowledge that lies underneath the surface of programming. Now when I code, I don’t just solve the problem at hand. I see different ways to solve it. I see other remote problems its related to. I appreciate the aesthetic of it all.

It’s not for everyone, but I find the mathematics underlying it all very beautiful.

And as for my day job in old-school-C++? Well, I hack together a prototype in Python in a couple hours, then spend a week translating it to C++ (adding verbosity, manual error handling, unfolding metaprogramming, etc). My boss doesn’t necessarily understand the whole languages thing, but he’s happy when I get a 2 wk job done in one. I’m happy too; having gotten through the icky bits of the problem in Python, I spend less time working on the boring bits in C++, and can move on to the next project sooner.

There is one last question, that I’m not sure I really have a good answer to. “Won’t you be tempted to use features that don’t exist in a normal language?” I’m hoping this will evaporate. Templates have existed in C++ since ’88 (pdf), various people have hacked lambdas in, and VC10 has added them for real. Short those facilities, it’s not like I have forgotten how to write imperative code. It’s still an option – I just now realize the development expenses of that option.

~

I’m curious, other answers do you choose for these question?

Best way to learn a Programming Language

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(Update, added Casting SPELs)

For better or worse, it’s accepted in our industry to be fluent in only a single programming language or technology. It’s lame, but there are plenty of excuses for this. “Turing equivalence” right? Finding quality tools is hard. And worse yet, to learn a new language you have to spend days and weeks reading some lame introductory text, right? Wrong!

There are tons of good intro guides out there that can get you up and running quickly, if only you know where to look. I’ve accumulated a bunch of these, and would like to spread the good wealth:

Learn You a Haskell, example image

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Comma Abuse

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Found this old C++ source file in my scratch directory, apparently from last September. I don’t even remember writing this, but it’s written using my idioms. If I did write it, rest assured it was primarily for amusement purposes (abusement purposes?) only.

#include <iostream>
using namespace std;

int fibonacci(int x) {
    int a=0, b=1, temp;
    while(x?(--x,temp=a,a=b,b=temp+b):0);
    return a;
}

int main() {
    int i = 0;
    while(i<10&&(cout<<"fib("<<i<<")="<<fibonacci(i)<<'n',++i));
}

Yeah. That was terrible. Terrible awesome. But looking back, I’m realizing that some of the comma abuse is superfluous:

int fibonacci(int x){
    int a=0, b=1;
    while(x?(--x,a=((b=a+b)-a)):0);
    return a;
}

Don’t let anyone check in code like this, ever.

Cache effects

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Quick call out to an illustrative blog entry on various cache effects.

http://igoro.com/archive/gallery-of-processor-cache-effects/

When someone bugs me about “X is too slow, because it has to make a virtual call”, and I get annoyed, it’s because a hot virtual call is an overhead of some dozen cycles or so.  Missing the cache?  In the thousands.  Don’t get me wrong, virtual calls can matter for many reasons, but that all flies out the window the moment you’re working on any non-trivial sized data set.  If your objects are 100′s of bytes large, you don’t worry about the virtual calls, you worry about shuffling their member slots around to squeeze more out of your caches.

“It better not allocate”

My other favorite perf quote from this month: “It better not allocate — this call needs to take 100 microseconds or less”.  On my dev box, on the default Win7 heap, an uncontended small allocation (and the pairing free) is 120 ns — or 0.12 microseconds.  My personal favorite small object allocator can hit down to 0.020 microseconds sustained.

We could allocate thousands of objects per call and still come in under budget.