Repository : ssh://darcs.haskell.org//srv/darcs/packages/base On branch : master
http://hackage.haskell.org/trac/ghc/changeset/5669f51e8bb1c0e57ada08e0962e015bf90dcbc9 >--------------------------------------------------------------- commit 5669f51e8bb1c0e57ada08e0962e015bf90dcbc9 Author: Daniel Fischer <[email protected]> Date: Sun May 29 19:33:57 2011 +0200 New gcd documentation Based on Ross Paterson's suggestion, a short explanation of the meaning of gcd, and a mention of possible negative results. >--------------------------------------------------------------- GHC/Real.lhs | 12 +++++++++--- 1 files changed, 9 insertions(+), 3 deletions(-) diff --git a/GHC/Real.lhs b/GHC/Real.lhs index 51d7db4..27b1b6c 100644 --- a/GHC/Real.lhs +++ b/GHC/Real.lhs @@ -520,9 +520,15 @@ x ^^ n = if n >= 0 then x^n else recip (x^(negate n)) in if even e then (nn :% dd) else (negate nn :% dd) ------------------------------------------------------- --- | @'gcd' x y@ is the greatest (nonnegative) integer that divides both @x@ --- and @y@; for example @'gcd' (-3) 6@ = @3@, @'gcd' (-3) (-6)@ = @3@, --- @'gcd' 0 4@ = @4@. @'gcd' 0 0@ = @0@. +-- | @'gcd' x y@ is the non-negative factor of both @x@ and @y@ of which +-- every common factor of @x@ and @y@ is also a factor; for example +-- @'gcd' 4 2 = 2@, @'gcd' (-4) 6 = 2@, @'gcd' 0 4@ = @4@. @'gcd' 0 0@ = @0@. +-- (That is, the common divisor that is \"greatest\" in the divisibility +-- preordering.) +-- +-- Note: Since for signed fixed-width integer types, @'abs' 'minBound' < 0@, +-- the result may be negative if one of the arguments is @'minBound'@ (and +-- necessarily is if the other is @0@ or @'minBound'@) for such types. gcd :: (Integral a) => a -> a -> a gcd x y = gcd' (abs x) (abs y) where gcd' a 0 = a _______________________________________________ Cvs-libraries mailing list [email protected] http://www.haskell.org/mailman/listinfo/cvs-libraries
