I'm working one of the Euler project problems, which asks for the
first triangle number with more than 500 divisors. I thought it might
be fun to use lazy sequences, and tried two approaches. One worked,
the other blew the stack. I'm trying to understand why the second
approach fails.
Here's the successful approach.
(defn tri [n]
(* n (inc n) 1/2))
(defn triangle-numbers []
(map tri (iterate inc 1)))
(take 1 (filter #(> (count-divisors %) 500)
(triangle-numbers)))
I have omitted the definition of count-divisors for the sake of
brevity. The failing approach is the same, except for an alternative
definition of the triangle numbers:
(defn triangle-numbers []
(lazy-cat [1] (map + (iterate inc 2) (triangle-numbers))))
This second approach dies with a stack overflow. Can anyone shed some
light on why?
Thank you.
David Cabana
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