Re^6: Algorithm for cancelling common factors between two lists of multiplicands

The precision is setable, but I had left at the default.

Increasing the precision to the point where it match or suppassed the accuracy of your Haskell code (a setting of 58), doubled the time it took to a gnat's under 50 ms:

[ 6:46:43.79] P:\test>MP-FET.pl
8.070604647867604097576877675243109941729476950993498765160880911582E-
+7030
  1 trial  of _default ( 49.865ms total), 49.865ms/trial
[download]

BTW: Could you explain something for me? In this:

cancel (x:xs) (y:ys)
    | x == y    = cancel xs ys
    | x < y     = let (xs', ys') = cancel xs (y:ys) in (x:xs', ys')
    | otherwise = let (xs', ys') = cancel (x:xs) ys in (xs', y:ys')
cancel xs ys    = (xs, ys)
[download]

I understand how it cancels between the lists, but I am confused about when it would pattern match against the second definition?

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Re^7: Algorithm for cancelling common factors between two lists of multiplicands by tmoertel (Chaplain) on Aug 11, 2005 at 06:20 UTC
The pattern `(_:_)` will not match an empty list `[]`, so the first definition will match only when both input lists are non-empty. If one or both of the inputs are empty, the second definition will match. Tom Moertel : Blog / Talks / CPAN / LectroTest / PXSL / Coffee / Movie Rating Decoder	[reply]