apfelmus wrote:
Henning Thielemann wrote:
apfelmus wrote:
Back then, I was given the task to calculate some sequence
of numbers which I did in one page of C code. So far so good, but when I
asked the task assigner about his solution, he responded: "Ah, this
problem, that's 1 line in Haskell. Well, 2 lines if the terminal is too
small."
Ah, a Haskell code contribution to the Encyclopedia of Integer Sequences?
The task was just for fun, but it's sequence A050000.
import Data.Set
xs = let f x m = x: let y = x `div` 2
in f (if member y m then 3*x else y) (insert x m)
in f 1 (singleton 0)
As said, it's two lines if the terminal is too small :)
I can't see how it could be one page of C unless the page is 10 lines
long ;-) The following code is the direct translation of your Haskell
code (except that it prints the result instead of building a list).
a+, ld.
#include <stdio.h>
#include <intset.h>
void f(int x, intset s) {
printf("%d, ", x);
f (intset_elem(s, x/2) ? 3*x : x/2, intset_put(s, x));
}
int main(void) {
f (1, intset_put(intset_new(), 0));
}
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