domingo, 8 de noviembre de 2009

Buscando el siguiente orden de magnitud

Viendo esta entrevista con John Hughes (creador de QuickCheck) me he quedado pensando sobre el último párrafo.

If you compare Haskell programs to C code or even C++ often, they are about an order of magnitude smaller and simpler. The same is for Erlang, those results are being validated in the industry. Where is the next order of magnitude coming from? I wish I had an answer to that question because it's hard to see almost. When you look at a beautiful Haskell program, how could this be 10 times shorter? But I think we need to be asking ourselves that kind of question. If I had a good idea there, I would spend the rest of my career working on it.

Realmente parece difícil reducir más un programa Haskell, como por ejemplo su versión de quick sort.

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

Comparada con la de C...

void qsort(int a[], int lo, int hi) {
int h, l, p, t;

if (lo < hi) {
l = lo;
h = hi;
p = a[hi];

do {
while ((l < h) && (a[l] <= p))
l = l+1;
while ((h > l) && (a[h] >= p))
h = h-1;
if (l < h) {
t = a[l];
a[l] = a[h];
a[h] = t;
} while (l < h);

a[hi] = a[l];
a[l] = p;

qsort( a, lo, l-1 );
qsort( a, l+1, hi );

¿De dónde va a salir el siguiente orden de magnitud?

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