Add a bit more explanation

maxsnew · Dec 22, 2014 · e5e9a4b · e5e9a4b
1 parent 9c9a4bb
commit e5e9a4b
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diff --git a/src/Lazy.elm b/src/Lazy.elm
@@ -136,6 +136,10 @@ pattern match on a value, for example, when appending lazy lists:
 
                 Cons first rest ->
                   cons first (append rest list2))
+
+By using `andThen` we ensure that neither `lazyList1` or `lazyList2` are forced
+before they are needed. So as written, the `append` function delays the pattern
+matching until later.
 -}
 andThen : Lazy a -> (a -> Lazy b) -> Lazy b
 andThen a callback =