<p>Hi, <br>
Then how about p2num, how to memorize this function.</p>
<p>Also I think it's okay to memorize this kind of function. The type system ensure all calling of montgKeys have the same type, e.g., it's a pure function without parameter, it's safe to memorize it since it didn't occupy more memory than representing dynamic generated types.</p>
<div class="gmail_quote">On Nov 6, 2011 11:06 PM, "Yucheng Zhang" <<a href="mailto:yczhang89@gmail.com">yczhang89@gmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Sun, Nov 6, 2011 at 9:35 PM, Bin Jin <<a href="mailto:bjin1990@gmail.com">bjin1990@gmail.com</a>> wrote:<br>
> Hi,<br>
> Since I actually didn't use the parameter in calculation, the return value<br>
> only depends on the type<br>
> of input, not the actually value. If it's impossible to cache the result, is<br>
> there another way to<br>
> memorize this "function" ?<br>
<br>
Sorry, I haven't considered about 'number parameterized<br>
type' when I answered the question.<br>
<br>
However, you can still use a data structure like MemoTrie [1]<br>
to memorize the function. The memorization is trivial, since<br>
you can convert between the number-typed 'undefined' and<br>
'Integer' with the functions 'p2num' and 'num2p' in your<br>
code. I've not tested, but this is an example using MemoTrie:<br>
<br>
> import Data.MemoTrie<br>
><br>
> memoMontgKeys :: (PostiveN p, Integral a, Bits a) => p -> a<br>
> memoMontgKeys = memoMontgKeys' . p2num<br>
><br>
> memoMontgKeys' :: (Integral a) => Integer -> a<br>
> memoMontgKeys' = memo (montgKeys . num2p)<br>
<br>
On the other hand, I think GHC is not expected to do the<br>
memorization automatically. An arbitrary number can turn up<br>
as the argument type of 'montgKeys'. This is similar to a<br>
function with an Integer argument, which GHC does not<br>
memorize now.<br>
<br>
<br>
[1] <a href="http://hackage.haskell.org/package/MemoTrie" target="_blank">http://hackage.haskell.org/package/MemoTrie</a><br>
<br>
<br>
<br>
Yucheng Zhang<br>
</blockquote></div>