Oops--I do get a stack overflow error if I give it 959 or greater as the 
argument, instead of 500.  It looks like the error is not from the explicit 
recursion, but is due to concat.  Someone who knows more than I do will 
have to explain this.

user=> ((fn pascal ([n] (pascal n [1M])) ([n row] (if (= n 1) row (recur 
(dec n) (map (partial reduce +) (partition 2 1 (concat [0] row [0]))))))) 
959)
StackOverflowError   clojure.core/concat/fn--3923 (core.clj:678)
(user=> (pst)
StackOverflowError 
    clojure.core/concat/fn--3923 (core.clj:678)
    clojure.lang.LazySeq.sval (LazySeq.java:42)
    clojure.lang.LazySeq.seq (LazySeq.java:60)
    clojure.lang.RT.seq (RT.java:484)
    clojure.core/seq (core.clj:133)
    clojure.core/concat/cat--3925/fn--3926 (core.clj:687)
    clojure.lang.LazySeq.sval (LazySeq.java:42)
    clojure.lang.LazySeq.seq (LazySeq.java:60)
    clojure.lang.RT.seq (RT.java:484)
    clojure.core/seq (core.clj:133)
    clojure.core/partition/fn--4309 (core.clj:2834)
    clojure.lang.LazySeq.sval (LazySeq.java:42)


On Monday, February 3, 2014 3:19:36 PM UTC-6, Andy Smith wrote:
>
> Hi,
>
> I am working through the 4clojure questions, I have a few different 
> solutions to problem 87 but all of them run out of stack space. I tried to 
> convert to using recur but I still have the problem. Why does this fail for 
> large n?
>
> ((fn pascal ([n] (pascal n [1])) ([n row] (if (= n 1) row (recur (dec n) 
> (map (partial reduce +) (partition 2 1 (concat [0] row [0]))))))) 500)
>
> Andy
>

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