Mirko Rahn wrote:
The following code is the direct translation of your Haskell codevoid f(int x, intset s) { printf("%d, ", x); f (intset_elem(s, x/2) ? 3*x : x/2, intset_put(s, x)); }No, not that easy. The Haskell code works with arbitrary precision Integer, the C code with a fixed size int. On a 32 bit machine, try to calculate a_{1805133}, which equals to 19591041024. Or a_{8392780} = 26665583616. Or a_{8500000} = 10804333. These values are calculated with the Haskell program in 370s and ~1GB memory usage.
This is also a work for a library (BTW like Haskell does), you can use gmp or mpfr. This will just add one line to store x/2 in y and avoid its recomputation. You will also have to switch from intset to set. And there one can start to see the difference. The code refactoring will be longer since C doesn't support parametric polymorphism nor operator overloading.
Fair enough, on the same machine a C program (*two* pages long) was able to calculate a_{23448481} = 594261577728 and a_{25000000} = 192365946 in 50s and ~1GB memory usage.
;-) a+, ld. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
