Every time I think about learning Haskell, I head over to haskell.org, read the Introduction link, and am offended by the astoundingly absurd quicksort example they provide for its superiority over C and leave in disgust.

First, let’s take a look at their Haskell implementation of quicksort:

    qsort (x:xs) = qsort (filter (< x) xs) ++ [x] ++ qsort (filter (>= x) xs)

Wait one second here! Something’s fishy. At the bottom, the basic operation quicksort does is a swap. Where’re the swaps? I don’t see any swapping. I do see splicing though; quicksort doesn’t splice. This isn’t quicksort; quicksort is an in-place sort, this thing here is a list sort. This is not just an implementation detail, it’s fundamental to what quicksort is. It doesn’t splice, it makes swaps. If you have some linked lists, you sort them with something like mergesort. But for arrays, you can’t beat quicksort.

Now, we can start on the C implementation they provide…

    qsort( a, lo, hi ) int a[], hi, lo;

Huh?

If you’re a C programmer, your first impression is to boggle at this syntax. It’s been deprecated for 17 years, and most C programmers nowadays probably don’t even recognize it. What moth-eaten tome did they dig this out of? Variables of hi and lo and h and l? l+1 and l-1 as expressions? That’s the kind of thing you see at the IOCCC. Let’s choose an actual decent example of quicksort for a more honest comparison, like the one from K&R2:

/* qsort:  sort v[left]...v[right] into increasing order */
void qsort(int v[], int left, int right)
{
    int i, last;
    void swap(int v[], int i, int j);

    if (left >= right)    /* do nothing if array contains */
        return;           /* fewer than two elements */
    swap(v, left, (left + right)/2); /* move partition elem */
    last = left;                     /* to v[0] */
    for (i = left+1; i <= right; i++)   /* partition */
        if (v[i] < v[left])
            swap(v, ++last, i);
    swap(v, left, last);        /* restore partition elem */
    qsort(v, left, last-1);
    qsort(v, last+1, right);
}

Much more readable than that strawman example they have on the Haskell intro page!
But it’s still an apples-to-oranges comparison, because the C implementation is doing a real quicksort, and the Haskell is doing a list sort. Show me a real in-place quicksort in Haskell: It’ll turn out looking almost like the implementation in K&R, I wager.

Now, Haskell was written by people who know their computer science. They know all about quicksort, they know their example is comparing different algorithms, and they can write better C code than what they use. Why do they have to be dishonest when promoting the virtues of Haskell, hmm?