Arithmetic-geometric mean: Difference between revisions

-- The result is considered accurate when two successive approximations are

-- sufficiently close, as determined by "eq".

agm a g eq = snd . head . dropWhile (not . eq) $ iterate step (a, g)

where step (a, g) = ((a + g) / 2, sqrt (a * g))

-- Return the relative difference of the pair. We assume that at least one of

-- the values is far enough from 0 to not cause problems.

relDiff (x, y) = let n = abs (x - y)

d = ((abs x) + (abs y)) / 2