问如何使用lambdabot获取前言中未包含的函数的源代码？

EN

lambdabot> src foldr
foldr f z []     = z
foldr f z (x:xs) = f x (foldr f z xs)

lambdabot> src flatten
Source not found. Maybe if you used more than just two fingers...
lambdabot> hoogle flatten
Data.Tree flatten :: Tree a -> [a]
Data.Graph flattenSCC :: SCC vertex -> [vertex]
Data.Graph flattenSCCs :: [SCC a] -> [a]
lambdabot> src Data.Tree flatten
Source not found. Just try something else.
lambdabot> src Data.Tree.flatten
Source not found. Have you considered trying to match wits with a rutabaga?
lambdabot> src Tree flatten
Source not found. And you call yourself a Rocket Scientist!
lambdabot> src Tree.flatten
Source not found. Just try something else.