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Going back to C
by buddhabrot

When I was 12 someone gave me a Metrowerks IDE to learn programming on my mac. I learned a lot with it, and got programming in C. I never really wrote a large program in it, only things like ROM hacks that extracted levels and models from snes/psx games I liked. Later, I got a windows PC and messed around with MFC in C++. That was the end for me, programming UI’s was too much work in C++ and I couldn’t handle the encyclopedic knowledge needed to program the Microsoft framework.

Later, I learned Java, which was also the language most commonly in my college. Making UI’s was a blast with it, I could factorize anything and really loved making as generic code as possible with it, even for small projects. Everything I made was made in Java.

Later in uni, I started learning functional languages, we used Haskell in one class. I got intrigued with Haskell and started solving Euler problems, up to this day I still have not written anything useful in Haskell but I love using it.

In the mean time I did some jobs for writing web sites. I used perl and php. After a while I only used php and used it more frequently.

After working for a while as a programmer I started to love higher-level languages, most of all Ruby. I became convinced that higher-level interpreted languages were the future because the slower execution times were to become meaningless. For any web projects I started using Ruby on Rails and to this day it still is my favourite framework.

Then, I learned Erlang because everyone was talking about it, and it showed me how to unleash parallellization, in whole new ways. I still think Erlang is the most amazing language I have ever seen. But then I found out it was also rather slow for the things I had in mind with it. I just didn’t find any use for it and never completely learned the language.

Last week I wanted to make a big poster of a fractal. I wanted to compute it on a friend’s octocore, and write a fast parallellized program. At first, I used Ruby, thinking it would perform better than I thought. And I quickly abandoned the idea because it was too slow.

Then I rewrote the same single-threaded algorithm in Haskell and saw that it was much, much quicker. But when I tried to parallallize it, I couldn’t fathom how to do it in Haskell and abandoned the idea. I tried to write a parallellized version in Erlang, and while it spreak across the machine nicely, each individual process was way too slow, the parallellized algorithm was hundreds of times slower than the single-threaded haskell.

Because I really wanted that poster, I decided to switch to C because I had this idea that nothing could fail in C. And I started to code in a language I hadn’t used for years, even a decade. And suddenly it hit me, everything made sense. Sure, I was writing so much boilerplate but it didn’t bother me. I suddenly realized that everything I wrote would be inside the program’s code, and that nothing more would. It was a great feeling.
I used simple pthreads to do the parallellization, and I used libgd to output my data to a png file. I started learning about mutex lock hierarchies to make the parallellizations overlap without endangering thread safety, it was all ugly code and the API’s felt horrible compared to what I was used to.. but it all worked out. The resulting program was thousands of times faster than anything I had written.

And now, I am seriously wondering where I have been all this time. Sure, I still think C is incredibly clunky. But now I got the dust off of my old course on writing compilers (Modern compiler implementation in C), and I want to write a compiler in C for a small programming language. I want to get down to earth again, and write things that are efficient and just run very quickly. I want to write lots and lots of code and know exactly what every line does.

Has anyone else had this feeling, this evolution? Am I going mad? Do you think C will last, and there are intersting jobs left for pure C developers?

I have the same question: Are there intersting jobs left for pure C developers?

In out the -- arguments to cat and less tells these utilities that no more options follow on the command line and not to consider leading hyphen (-) in the following list as indicating options. Thus -- allows you to view a file with a name that starts with a hyphen… -- argument works with all Linux utilities that use the getopts builtin… This argument is particularly useful when used in conjunction with rm to remove a file whose name starts with a hyphen (rm -- -fname)…

A Practical Guide to Linux Commands, Editors and Shell Programming (p. 442)

via Handling Filenames with Spaces in Bash

Requirement:

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How to use it:

1. Download weather.py.
2. Edit the file, fill in required parameters (read CONFIGURATION first).
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x = 5
y = 3

temp = x
x = y
y = temp

We need a temporary variable as a container to hold a value first then do the swap.

What if in some situation you can’t use the extra variable? How would you do it?

Well, let’s forget computer programming but pick up some little math we learned in elementary school:

x = 5
y = 3

x = x - y (=2)
y = x + y (=5)
x = y - x (=3)

Here we go!

Merry Christmas, everyone!

Here is my solution:

class Foo
{
public:
    Foo(const Foo& f) {}
    static Foo getAnInstance()
    {
        return Foo();
    }
private:
    Foo() {}
};

Explanation:

To prevent users from creating objects on heap, I basically can’t give them any public constructors (ctor); therefore, I need to write at least one ctor myself and make it private since if I fail to do so, the compiler will generate a public default ctor for me and that is exactly what I don’t want. Then the user can only use the static member function getAnInstance to get an object to use.

Analysis:

In fact, my solution contradicts the explanation because I actually have a public ctor — the copy ctor. The copy ctor makes the following usage work:

Foo f0 = Foo::getAnInstance();

But because there is a copy ctor, after the user get his/her first object, he/she can do the following:

Foo* f1 = new Foo(f0);

This is saying that my solution can only guarantee the first object is on stack and it can’t go further.

So, my solution fails to solve the question.

p.s. I haven’t really seen the point of the interview question, but it’s interesting to think about ;)

Update:

The correct solution is to overload the new operator and make it private. Credit to DANIWEB

When you are going though a document in VIM, you find a word and you want to go to the next same word in the document, you just need to put the cursor on the word and press * (SHIFT + 8).

What if you want to the previous one? Answer: # (SHIFT + 3).