changes, thanks, integrate example

1 files changed, 9 insertions, 2 deletions

diff --git a/examples/integrate.hs b/examples/integrate.hs
index 10f0269..3a03da6 100644
--- a/examples/integrate.hs
+++ b/examples/integrate.hs
@@ -4,14 +4,21 @@ import Numeric.GSL
 quad f a b = fst $ integrateQAGS 1E-9 100 f a b  
 
 -- A multiple integral can be easily defined using partial application
-quad2 f a b g1 g2 = quad h a b
-    where h x = quad (f x) (g1 x) (g2 x)
+quad2 f y1 y2 g1 g2 = quad h y1 y2
+  where
+    h y = quad (flip f y) (g1 y) (g2 y)
 
 volSphere r = 8 * quad2 (\x y -> sqrt (r*r-x*x-y*y)) 
                         0 r (const 0) (\x->sqrt (r*r-x*x))
 
+-- wikipedia example
+exw = quad2 f 7 10 (const 11) (const 14)
+  where
+    f x y = x**2 + 4*y
+
 main = do
     print $ quad (\x -> 4/(x^2+1)) 0 1
     print pi
     print $ volSphere 2.5
     print $ 4/3*pi*2.5**3
+    print $ exw